Duramax and Powerstroke are V configuration. Twice the valvetrain movement as the I6 Cummins. Also the cummins is straight cut gear in comparison to the heli cut gear of the Dmax and Powerstroke. Straight cut gears produce no forward torque
Okay. Obviously, it is not. My point is that there is more shear force on the valvetrain of a V configuration than an inline configuration. That is why inline motors are far superior in longevity than any V configuration. It is simple geometry. With pushing the valvetrain to opposite angles, you can not deny that the force placed on the camshaft is exponentially higher in a V. But I am stupid, right?
@@danielmattiello4404 Stupid, *maybe not* , but the force exerted on the cam is only 25% more, on a V8 engine, and there isn't an application where the location dowels take the force anyway, the vibration damper *pinches* the timing gear in place, *that* is what holds the gear, the pin only *locates it* it *DOES NOT, and WAS NOT* designed to carry the load. If you left a Cummins damper bolt loose, it would rattle itself loose enough to destroy shit, just like the Duramax, and PSD, been fixing them since they came out, more than 20 years, bud.....
@jamesgeorge4874 Now, what i am talking about. I could care less about the brand. The only thing that matters is the gear cut. Cummins is straight cut. 90° to the crank. All force turned by the crank gear is turned at 90°. There is no walking of the gear. Now, the PSD and Durmax both have Heli cut crank gears at my best guess of 35- 40°. No matter how hard you try, you can not stop a heli cut gear from walking. No different than a pinion. Hence , they blow through a dowel and not a keyway. Keyway allows walking in the given area and still staying in the line of work. I'm not trying to bust your balls, but I do know what I am talking about. Honestly, if you could put a straight cut gear in a PSD, it most likely would not shear off the dowel. Why do you think all high HP motors run straight cut gears? Less issue with mesh at higher rpm and out of the diesels PSD and Duramax are the highest rpm range.
Industrial mechanic here, if I were to design all three I’d used a half moon or woodruff key with gear being an interference fit; needing heated to put on. I’ve seen a lot of keys and pins sheared in different applications and this is the strongest I’ve seen. My second choice would be a regular key in about 1/4 inch with interference fit but key stock is usually not hard enough to last extremely long times but will give a bit before shearing. Pins are usually hardened which means they are all or none. They’ll just shear with no warning, there is no give.
I'm not a engineer but I'm a old man who has been a mechanic for 40 years now and I have to say that it is the way the gears are cut and it's a angled gear and it's going to apply more force than the straight cut gear. I don't have a technical answer to why the Chevrolet and Ford doesn't have keys and should be headed and pressed on to the Crankshaft. The ones that are on the Ford and Chevrolet engines along with the angle gear cut and the extra pressure with out the keys to hold them with being have to be pressed on and off along with the cost cutting to save a few dollars along with the gear cut on the Ford and Chevrolet Diesel engine. Why would you do something that is not a solid and durable to save the extra effort to machine that key way and pressing on and off of the gears with the angle cut is a good recipe to fail. Your videos are proof of the cost savings for the manufacturing process and then passing it along to the customer that is going to use these trucks for medium duty towing and heavy duty work trucks is not a good recipe for the next purchase of a truck by the customer next time they are going to look at the Dodge diesel for the reliability of it over the others. Both should have been recalled to fix this engineering dept flaw or screw up. Going to be a repeat of the 6.0L in the older Ford truck not only for Ford and the Chevrolet Diesel engine. Hopefully you don't laugh at me too much for my answer 🤔😉
@@lonerider5315 even though I have assembled a changed a ton of motors for my friend's, customer base, and family, I have never been told of anyone of my engine's or transmission jobs fail. Wear out slow and sure as they should but never had issues like that but I have been tacking gears on stuff like that since I was in my early 20's and I learned that from a Old Time Tanker mechanic from WW2 and Korea and it never failed him and he was a great talker of a little bit of insurance never hurt anyone or anything. I would say I love to learn something daily if possible. Good day to you and thank you for the information.
Bingo! Big corporations only see numbers, so when it comes to choosing good steel and shit steel for your high stress components they only care about the profit margin. It just has to make the warranty period, then it's your problem.
From what I’ve heard through researching this issue it seems to be when the truck has been worked on and not torqued to spec. When re installing the balancer if it’s not torqued to spec it can take out the dowel pin. The pin is only there for alignment purposes.
so your implying theyr torquing the cummins to spec and not the duramax ? why would a large sample size of mechanics do it right on one motor and wrong on the next?
@tx6695 I think what they're saying is the duramax balancer has to come off to do jobs like the water pump, so when it's reassembled the crank bolt isn't tightened to specification allowing the gear to spin and shear the pins. On the other hand, the cummins balancer doesn't come off for the water pump so the bolt is never touched, the torque is never changed, and the pins are just fine. Plus I think the cummins press fit interference is tighter than the duramax.
@tx6695 i definitely agree with the powerstroke stuff!! The dowel pins are really just there for the alignment of the gear not necessarily to keep the gear from spinning. It's the torque of the crank bolt against the balancer that's 'supposed' to clamp everything together.
Is so nice of you to make these videos for the public thanks , I always like to instruct my self with these types of content’s but I like to instruct my self with with the comments of the communities thank you again Blessings
It's the loading and unloading of the gear on the duramax and it being helical so there's forward thrust also on it , having a pin sideways like that greatly reduces the sheer strength of the pin , had it been pinned like a ls balancer gets pinned for a supercharger and like how the key you guys do is installed it spreads the load an immense amount along the snout and will always be stronger probably by thousands more psi of load capability. The cummins gear is straight cut that eliminates the thrust right off jump , it's press fit so even if it could move it'd likely gall the snout and lock 1st before the pin ever sees that full load produced.
Lots of good answers. Most are pretty straight forward explanations, not "rocket science". This stimulates me to ask "how did something so easily explained by the public escape the engineers"?
@@terriecotham1567 Hey terrie. People have used this "book smart no real world " response for years. It used to be the favorite comeback from guys talking shit about their coworkers that had a diploma full of ASE certs. I would always listen to these guys that had trouble taking tests but I would finally get around to asking one question, That question would be "can't a guy have his ASE's and also have excellent hands on talent"?(of course you could) Having your ASE certs does not mean you are no good hands on.
@@danielrose-tt7os I was talking about those who have came out of school and never gotten there hands dirty. Yes they can do amazing things on paper with math and computer's And those with ASE Certified technician's for the most part have some hand on experience. But many times things come out of the Auto makers and come up short to getting the job done. Perhaps it seems like a good idea to do away with the key slots and install pins. And on paper it looks great. But in all truth it's a major weak point. Those with advanced Eadcation can at times make big advantages in every thing and can also get it wrong. Just look at some of the engineering in today's car's from engines to the computer control systems and tell me they are that much better. When repair cost are mixed with the cost of the parts. One of the most advanced things in car's for the cost was the induction of the electric Ignition system. Doing away with the points and ensuring a longer lasting in performance. When you have to spend 2 to 3 hours just removing things to get to the Vale covers that's not an advance in service When you run a cooling hose through the middle of an engine and it's possible you have to tear down parts of the engine just to replace a hose that's not advanced When you make plastic parts like a vale cover or oil pan that can't be reused that's not advanced. Car's have become High price computers and Software control systems. Are car's All that advanced if you work as an ASE Certified technician's in any shop hard to believe you think spending an hour just to replace an Oil filter is advanced Eadcation and well engineering Hard to believe your happy with the lay out of some parts or the time it takes to serve them. Those with ASE Certified papers hanging on the wall have worked for them and Lear many things others have not. But at times those with real hands on every day experience who work hard and learn as well at times have a better idea. I wasn't trying to put down anyone from college just trying to point out how all those in the engineering team came up with a bad idea.
Before even considering any gear loading it appears the Cummins gear has 2 advantages- More surface area to hold the press fit mating the gear to crank and also the I D to tooth root is dimensionally larger maintaining that press fit with more mass to to maintain the press fit as well.
Helical gears have more surface area. The tooth is longer for a given gear width. They are therefore stronger than straight cut gears. They are also quieter running but do have power loss due to the side loads and additional friction caused by the longer tooth form. You pays yur money and you takes yur choice.
I’m only talking about the surface areas of the shaft to gear internal dimension. Gear tooth contact surface area for this discussion has no consequence. But as a random factoid unrelated, you are correct.
I'll take that. I guess it might relate to the machine tolerances of crank and pully as to the maximum and minimum clamping force bandwidth avalible. A minimum tolerance crank and a max tolerance gear might be enough to cause issues.
Without getting too technical, although I’ve enjoyed reading the technical comments here, I think the answer is obvious. First, the inline 6 engine is arguably the most sound engine there is to offer due to its almost perfect harmonic balance amongst other things, and Cummins, not Dodge, has been producing quality heavy duty engines for decades. Their name is world known and trusted, because they have proven many times over that they know what they’re doing.
Exactly, I was taught years ago the pin or keyway is only there to align not to hold in place. The bolt does the job of holding it all together and if not tight that will transfer the load to the pin or keyway. Also watch out for a bolt that has been over torqued and is bottoming out.
@@philip_james Bingo. I was taught that same thing over 30 years ago, by a veteran diesel mechanic with 30+ years of service and instruction experience, at the time.
So I have a number of thinking out loud questions. 1) what does the duramax, powerstroke and Cummins have to rotate with that gear? Fuel pump, oil pump, cam ect.. 2)how many teeth (outer diameter) of the gear is each one? Does this remove some applied stress because the gear is smaller? 3) how fast and hard does the torque come in for the powerstroke or duramax? 4) whats the press fit tolerance for each one? Does having a full length key way help or could you get away with the proper press and small alignment down? I kind of like this game of asking questions and giving people the opportunity to answer.
The added variable I haven’t seen mentioned yet was; which injection pump is in the system and has it been modified ? What is the required rail pressure, did those bosch pumps fail prior to the crank gear shearing or spinning? On top of that , the difference between valve-train torque requirements, and straight cut gear vs helical cut gear .
Comes down to a couple different factors for starters the gears them self have a massive difference between surface area on the contact surfaces of the crankshaft second the dura max is a v8 it’ll have more spring tension on the gear from the cam shaft and extra components
The harmonic dampener is not pressed on for Dmax applications. The torque from the fastener clamps the dampener to the oil pump gear. The pin is simply an alignment feature. The pin sees zero torque. The dampener bolt comes loose (happened in testing), the pin sees torque and sheers. Dampener rotates causing engine misbalance and low/no oil pressure in worst cases.
Straight gears are always more powerful the sideway gears have the ability to have the gear go forward and back therefore less stress on the pin that's why Cummins rule..
I think on the duramax a lot has to do with you need to remove the balancer to change the water pump and people do not torque the balancer when they put it back on.
It’s definitely this! Bunch of yahoos thinking it’s ok to just send it. Torque specs are important for a reason, especially on the higher ends of the spectrum
From my experience it's usually because someone removed the balancer to do a water pump or something and they don't replace the balancer bolt because they are torque to yield bolts and they don't torque it to spec.
That’s a theory, but a buddy of mine had them sheer in 2 different trucks. One at 78k and the other 99k, neither of them had the balancers ever removed. GM wouldn’t honor the warranty
My uncles solution for that is to take a 1/4" drill bit and drill right between the pulley and the crank snout and then Hammer a dowel in the long way.
So you drill a hole through, weakening both components and possibly starting a stress crack, then pound a steel pin in the hole, adding additional stress the components weren’t designed for. What could go wrong?
The cummins gear has a bore diameter spec of 2.515-2.517in and the crank has a spec of 2.5193-2.5201in. The gear gets heated to 350° for about an hour and installed. All info straight from quickserve
Yep this here, once gets hot gear can expand enough it has room for the pin material to fill. The pressed one is so tight there's no where for pin material to go so it holds better. That's aside from that tighter diameter helping to hold it. If you removed all other forces and had only pins but no where for the pin material to go when force is upon them they'd still hold. Of course such a set up is impossible but the physics is more understandable thought of in that way. Kind of how even something soft as oil can hold and push things around when it has nowhere to go, hydraulics work too though.
I'm guessing the dowels are just there for timing and not holding the gears. The Cummins gear is more than twice the size of the ohers so the press or interference fit is holding it much more securely with that much more area
@@tomroe7715So with what I see and that you state the pin needs to be in place my guess would come down to the tempered strength of the dowel pin. Resistance on the valve train could also be a contributing factor.
@craigtimmons3468 yes sir, usually when I get a new motor or rebuild one, whether it's max, cummins or especially the 6.7 for I put 3 small welds on the cam gear. I just had a brand new rebuild come in from a company in Canada and we didn't tack the gear. Well it turned. The motor was sent back blowing air out the two intakes. If I could send video I would. BTW 36 yr master cert ford and chevy tech.
@craigtimmons3468 consider when a gear is pressed on, it will distort a small amount no matter how careful you are. The heating process and yes torsional from valvetrain do the rest. Tacks are mandatory.
So please be patient with me . The other year I replaced my water pump on my 08 Duramax and it took me a long time cause of my many back injuries. I only learned about the shearing off of the pin and it’s better to install a key way . Can that be done wo pulling the engine and just removing the grill , radiator and water pump ??
@@eddiereyna2998 My point was that the problem will occur if you didn't apply the correct torque. Retorque it if you are concerned. To answer your question, yes you have to completely disassemble the engine to get the crankshaft machined.
@@davidmitchell7183 thanks for the response . Tis will be sometime before I can save to get this taken care of. I just recently paid over $5,000 for a new CP3 pump and some injectors and glow plugs but the truck would still go into limp mode . After the 2nd time of taking it back it did it again . Now I’m on bed rest for 6 weeks from a surgery. Oh well , let’s see how the world turns . I appreciate your input .
@@eddiereyna2998Take care of yourself before the truck.. Find somebody local that is good at diagnostics. In my experience, I saw quite a few rubbing wiring harnesses and electrical gremlins.
@@davidmitchell7183a Chevy with electrical problems... no way! Lol. I say this because I've driven (never owned) many a Chevy as an hvac tech and every last one of them that I had for any length of time had an electrical issue. One problem child left me on the side of the road three times before the problem was fixed. Bad spot in the crank pos sensor wiring.
Many correct answers here. The pin is there to position the gear's angular relation to the crank. The difference HAS to be in the adequacy of the shrink fit. The Cummins is thicker between the ID and the valley between the gear teeth. More metal means more pounds of tension even with the same shrink.
Torque is the enemy. The only way to spread the load evenly from a torque aspect is more main bearing surface area. An inline engine inherently spreads the load service across the mains because there are more of them. If you can spread the torque load across the entire engine you’re eliminating the moment of inertia on the crank snout/gear.
Mech-E here. I would say you are dealing with difference in torsional vibrations between a V8 and an in-line 6. There is a reason you don’t see over the road trucks with V engines. In-line configuration are producing a sine wave vibration on one plane rather than 2. There is still a lot we don’t understand but we can measure it with problems like dowel pin shearing or crank failures. Also, someone said it earlier but helix cut gears provide a bit of forward torque where square cut do not. Trade off it noise.
I was thinking the straight cut gears efficiency verses the heli gears quiet. Cummings are for stump pulling and Duramax are for getting groceries. The Ford is in between.
Please explain in engineering terms what "forward torque" is. I am also a Mech-E and I'm unfamiliar with WTF that is. Perhaps you meant to say the helical-cut gear is subject to an axial thrust when being spun??
There are thousands of V configurations out there, dozers, big loaders and graders, haul trucks, power generators, locomotives and excavators. Road tractors don’t have V-configurations anymore because they wouldn’t fit under the hood. The V engines put out way more power too. No other reason.
Hi, In my humble opinion, Cummins are one of the best engineered engines ever built. I’m sat above a 25 year old M11 in an English made ERF (1999 model) it still runs perfectly after a million miles! The stress that goes through a drive train like that requires a very very tight interference fit with a woodruff key to align it. Better still is a taper fit drive with a woodruff key which never ever fails if assembled properly. It’s all down to the cost of production. I’ve never worked on one as we don’t have them in Britain but it seems to me that Duramax is made to a cheap budget and that design is always asking for trouble! Thanks
Cummins are simply GREAT engines if maintained correctly . A straight 6 Engine is naturally balanced - Phyics . My father told me about Straight 8's :" They were so smooth " .ROBBIE - Australia 😊
The V8s should in theory be more robust since they're doing more firing pulses in each revolution, so torsional pulses and valve train loading wlil be less pronounced.
Took the words outta my mouth, man! A soft pin or hard pin aint gonna help of the crankshaft slot/keyway is poorly fitted. Hard crank, hard pin, would maybe 100% solve the issues, except IF it slipped the crank AND the resr of the shaft (giggity) is ruined. What all runs off that gear? Fuel injection pump? Only timing? Both? I'm more gasoline or nitro type of dude, but pressfit unless it's a temp differential plus like 0.003" interference fit, freeze shaft, induct heat gear, press on, etc that might work for pure stock stuff...... How much lubricant is moving around in these various drive scenarios? Not enough or too thin a oil/oiling system would stress that crank snout and gear pretty dang fast. But hardness tests first. Even some hazard frought files just to get a idea what the relative hardnesses are. Then magnaflux, cuz could be fine on metallurgy but have manifacturing impurities and tiny tiny cracks. If I had a wasted crank in my garage I'd go full cut off wheels and torches, cut it up, sand and polish, stare at magnified sample bits of metal and deduce something. Most likely some sort of hardness and oiling/lack of oiling, car gods hate you and want you punished... Normal shit😂
@threadtapwhisperer5136 I'm gonna go with "angered the car gods". They obviously didn't burn the correct incense or anointed it with blessed oils that you have sworn at/bargained with/begged to work
That was my first thought too. @g1channel found the specs (precise!, if manufacturing can consistently do it), and Cummins heats up the gear before putting it on, not sure if the others do, could by they have to as well. Also, metallurgy, surface hardness variables.
I'm not sure if they're made of differently tempered metals, or Chinese vs. Canadian steel, but that could certainly have an effect. The width certainly has an effect in a press fitting, but the Cummins needs the width because it has so much torque. The inline 6 is better balanced, which means less impulse would be felt by the dowel pin, which I have effectively seen mentioned.
Id have to assume that the press fit is tighter, so the dowl is purely for alignment. Gear is probably dropped on hot then dropped on like a press fit bearing is installed without a press, so they don't spin or walk back off wonce in place. Thanks Dave.
Finally someone said it. I'm sure the balance of the inline 6 has some effect on the dowel pin breaking, but the main culprit is that right there. There's no diagonal load on that straight cut gear, only single dimensional.
No they are all straight. Torsional forces are the enemy, brand doesn't matter. Helical are never used in this application because of torsional forces that would require special bearings to keep both shafts centered.
Cummins uses press fit and the pin when ford only press fits and duramax only uses the pin. I believe that is why it happens. Also cummins is a inline 6 and dont rev as high as V8’s do. With 2 extra cylinders and higher revs, its more stress on the gear and helps cause the failure
the durmax will runaway from the cummins when i was in the army 2 knuckle heads in my shop bought diesel pickups even thought they didnt need it after deployment, both 3rd gens because thats what they could afford in 2014 the duramax smoked the cummins both had chips and a down pipe. cummins might tow better an last longer but 8 holes lighting the fires is definitely faster
@@akabruno1 Duramax isn't Isuzu. GM and Isuzu partnered together in 1997 and created Dmax LTD. All 6.6L Duramax engines have been built there. Isuzu never made the Duramax. It was a new build when it was introduced. All 3 manufacturers had help with their engines. Cummins and Case. Ford and AVL.. What's the issue??
Electrician/racecar mechanic here. The harmonics created from the V8 configuration create stress on the crank. I6 is smooth when it's not breathing engine farts.
Straight six has a more distributed load and more balanced, maybe. The V motors might have a mixture of high vibration and torque load not being linear.
One thing that I have noticed is when you turn these trucks off, you hear a loud screech, which is the belts and all of the front end accessories still spinning for a fraction of a second after the crank comes to a halt. That is quite a bit of rotating mass coming to an instant stop. With the tension that is on these belts, I believe this has a lot to do with shearing off the dowel pins.
I was once running a cup car engine on an electric transient dyno. The exhaust temp failsafe had been mis-programmed to initiate a "hard stop" rather than a "cooloff run", meaning once the EGT hit the limit, the dyno controller cut fuel, cut spark, and applied FULL dyno braking. That engine went from 9200rpm to 0rpm in one half a crank revolution, according to the datalog. Before running the engine again, we checked valve lash and ensured the cam degreeing was still correct - it was. Engine ran like a champ afterwards. Zero damage, much to our surprise. Engine had a belt-driven cam; dunno if that made any difference.
Inline engines close to being perfectly balanced and from experience I have found V engines to have much higher vibration. I also believe on the Cummins the dowel pin is for alignment, not retention. Right now I drive a medium duty vehicle with a Navistar VT 365 engine and I will admit it resists spooling up partly because of it's V-8 configuration....but in the past I've use 5.9 and 6.7 Cummins and they very readily spooled up in indicating much less torsional stress.
the press fit of the cummins is actually absorbing most of the load placed on the gear. the pin is merely for alignment/timing purposes the duramax is shearing the pins of during a deceleration cycle due to the compression loads placed on the upper half of the engine and fuel system
Working in construction, I have noted steel hardness varies from area to area in the continuous 48 states. I have also noticed that older steel is much much harder than new steel, I assume the mines used then were from the US vs foreign
Material composition. Heat expands and contracts as we all know but the material for these 2 products are from 2 different companies that use different iron makeups from China/Argentina/Mexico etc. well when it's under pressure and friction occurs the dial pin within the 1/16th of gap friction occurs and completely gives way.
I also agree with straight cut gears vs helix cut. I would also add that Cummins gear has full width gear vs half cut gear of the others there by spreading the torque load to the entire width vs have gear causing more torque in that area hence it’s basically a lever.
Cummins has experienced with semi engines. So they make their small engines using the same tried and true methods as their larger industrial engines. My Cat c15 had a the same setup as the Cummins.
I worked for dodge when they were having issues with the nut that held 5th together on the 5 speed backing off. My understanding is ford who used the same trans didn't. It came down to harmonics. The 6 cylinder had a different frequency than the 8 so the nut came loose. I wouldn't be surprised if the same thing was happening.
CAT has a V8 V12 and V16. It's all about clearance and materials. If you go cheap on materials like Chevy and Ford you get what you pay for. You upgrade everything to high end shit you get better results.
Serviceability is trash, and also its simpler to in line. Simple means space. Space is Serviceability. Space is cooling. Space is auxiliary modules. Space is more turbo, more Radiator. Vertical engines also see less wear and oiling issues. The more flat you make it, the higher your woes with oil and uneven wear.
On the cummins the gear is a press fit and the pin holds it from sliding side-to-side. On the Duramax the gear is a loose fit and the pin holds the gear from rotating along the rotating axis. This pin is subject to various load stresses, as engine speed, horsepower and load are transferred to the "holding pin".
@@wm2086 yeah the duramax isn’t a “real” diesel. It’s not like they are the engine of choice for thousands of military combat vehicles like the armored Bear Cat. Those engines see combat but of course there’s always a butt hurt Cummins fan boy around somewhere
I haven't worked on these series of GM or Ford diesel, but a hell of a lot of the earlier series. But do work on a lot of Cummins and Dietroit. Factory trained cummins, detroit, cat, allision, voith, and ZF. The Cuminns harmonic balancer, when bolted up, does not use clamping force against the gear. It is a flange to the front of the crank. The gear is heated to about 290 deg and pressed on. Both of the other engines discussed do use clamping force to secure both the balancer and timing gear to the crank. I would bet that the bolts are being reused. Detroit diesel on most of their inlines, series 50 and 60, specify new bolts on the front and back, IE: harmonic balancer and flywheel or flex plate. Also most manufactures specify a hour or mileage for harmonic balancer repladement. There is a reason for this. The balancer is a "harmonics" balancer. The outer and inner are pressed fit over a medium that allows torsionaly movement. Some are part of the actual balance of the interanal rotating mass. When the mass as a whole is not in balance it can cause bolts to be stressed and cause stretching which of curse causes the clamping force to weaken. I have seen long drive shafts in coaches that are out of balance ruin rear planeteries in automatic transmissions. In manual trans they will wipe out thrust bearings and harmonic balancers. Cummins has literature on it. I have discussed these issues with the Western US engineering tech for fault analysis from cummins.
The cummins gears are a really tight interference fit. Once its on theres a special tool from cummins to drill into it till it relaxes. It was a common thing on the isx family, but the b,c and L series are similar
Duramax has never been made in China. Good try. It's built in Moraine Ohio. The refinery is in Defiance Ohio. Nice try. Powerstroke is built in Mexico. All Cummins powered Stellantis trucks are too...
The reason is the difference in how the gears are cut, just as many have mentioned prior to my comment. Straight cut gears have no vertical torque placed on it, so it stays in place. the helical gears have vertical torque due to the design of the gear, so over time you will see the gear start to walk, and eventually come loose. The fix is to convert the Dmax and Pstroke to straight cut gears (if possible), or do a key install or weld it in place. Straight cut gears are far superior to helical gears.
Part of that may be attributable to the loads of V engines valvetrains and also possibly attributed to the type of harmonic damper being used as well...for those who thinks inline sixes are just better, I remember the days before Houdaille viscous dampers were adopted and installed, (by Cummins & other manufacturers), big inline diesels would snap crankshafts right behind the #1 rod throw...yes, I'm that old and have that much experience...
I'm a Materials Scientist and I would suggest the reason for employing different methods of limiting gear damage is to use such ways. But the reason is the manufacturers have tested the components to failure and know how much is the safety margin. Engines are built to a cost and to minimise costs cheaper methods of assembly are used Undoubtedly the long keyway is the strongest most expensive method. I'm no Automotive Engineer but my answer is based on my work on understanding steel and its composition and heat treatment. I worked at JN Kirby Products Rockdale Sydney Australia. I certified Materials to specification for car parts and assembled units for car manufacturers.
Personally I think it happens during engine shut off when the compression causes the motor to run backwards for a second and then snap back forwards the old 12 valve Cummins makes the belt squeak it happens so hard so if that's what's going on I would understand why
The straight cut gears on the cummins will put less torsional force on the pin thus limiting distortion on the gear body and increasing force on the pin with load changes. Straight cut gears are louder and will steal more power but can transfer more power assuming proper gear meshing.
To give a thoughtful answer we need to know the pressure of the press fit or at least the interface of the fit. (0.001" =7 tons/inch of shaft in mild steel). The Cummins gear has a consistent pressure width due to the design whereas the other gears do not. Personally I would never install any of those gears without the appropriate loctite.
Fits and vibration are contributors but the helical cut naturally tries to push and pull the gear out of place if nothing else it fatigues the pin. It would be interesting to see the pin shear in relationship to rotation direction.
I'm at 350,000 miles after a pressure relief valve issue, and new melling at 278,000 miles same pins in crank and torqued it to spec. By degrees and it is still holding
I am a engineer for non automotive machines. I can see a major problem with the gm/Ford gear design. First, straight cut gears are stronger than helical cut gears with the drawback of being noisier. Second, the gm,Ford gears are almost half the width of the Cummins. More surface area on the thrust surface to spread out the load. The industrial equipment almost exclusively use straight cut gears in load carrying drives.
I would say it probably had sumthing to do the the Helical cut gears, and/or shorter crankshaft, but being shorter might not matter just depends on the thickness of the journal size and robustness of the crank and how hard each power stroke hamners that gear and how that gear loading affects the fit to the crank
Would be interesting to know how many of the engines that experience this failure have had the balancer bolt removed and reinstalled for service vs undisturbed. If the majority are undisturbed, it might be due to crank harmonics from the V8 vs I6. Simply retorquing the crank balancer bolt periodically should prevent the failure. Those dowel pins and shrink/press fits were not designed to take the full torsional load from the valvetrain. The design has no failure tolerance for inadequate clamping from the balancer.
My guess would be people aren’t torquing bolt after reinstalling it. The pins are for alignment only the balancer is press fit and is held by the bolt. So, it could be a factory issue too, not getting them tight. Just my two cents.
When you combine the helical cut of the gears instead of straight cut like on the Cummings plus you add the press fit of the Cummings versus a non-press fit of the Power Stroke and Duramax. There’s the two reasons right there… 100%! I am an engine builder and an engineer, and I have methods to even include more power than what you folks and Gale Banks are doing/making! Best regards; Edward Heath - engineer at: “new ideas and innovations, LLC“ out of Madison, Connecticut, USA
Material used in making the dowel pin. Positioning of the pin under the gear. Depth and tolerances between the dowel pin and the slot it's seated in. Gear ratio differences between each gear.
The lash can’t be adjusted, so proper manufacturing is critical. If you introduce harmonic vibrations by modifying the valvetrain(stiffer springs, bigger valves, etc) or raising rpms above design limits, the force of those loads can destroy the gears quickly. Caterpillar added counter weights to their C-15/16 cams because the vibrations got so bad when cam driven fuel injector pressures went well beyond 10K psi. Another example is a Coyote V-8. The oil pump is fine at stock rpm. Raise the limiter and you might as well start an office pool for how long it will last before the oil pump gear shatters. Harmonics can be very powerful, and sneaky.
Straight cut gear causes the gear ratio change as it spins from tooth engagement at start to middle to un engagement! Plus and more backlash and less forces and contact time of the amount of torque into gear on crank
I believe the metallurgy of the gears vs. the crank are different enough that its loosening when hot. This causes the gear to smack the dowels from side to side causing the shear. Full length keyways are superior.
You spoke of press fit, is the pin being used predominantly as a install/index guide or as an anti-rotation device. It performs both, but must be sized/designed appropriately to perform as an anti-rotation device based primarily on torque drive required, interference fit and vibration environment.
First off, the name: Cummins are known for great R&D. While many are saying the harmonics and internal stressing of V configuration. Helical cut gearing puts undue stress by the gearing can not equate because of the centering effect if the driven gearing. Cummins inline is just a better design.
Take a micrometer and mic the contact areas of where the gears sit on the shaft, it should be a size for size fit or a tight bore and a nominal shaft. If it’s loose it will allow for play and can shear the pin acting as a key. Just my thoughts on that
Two reasons I can think of. One the inline configuration of the Cummins has less harmonic vibration. The second reason I believe is because the front gear is not only pressed on but it also has the dowel pins. I believe if they were to press the gear onto the Duramax along with the dowel pins it would eliminate the problem for the Duramax and if they added pins for the powerstroke along with the pressed on gear it would strengthen it as well.
Cummins dow pin is a locator pin used as a stop if the gear spins as its tighter on the crank. Chevy and Ford gears put a constant load on an undersized pin with a gear that can slip due to looser tolerances.
Well right off the bat there may be an application issue because dowel pins are primarily used for locating and not for handling High Shear loads. Take a look at the cross section of a sheared dowel pin and you will see that typically it's grainy and it cracks and this is the result of being very hard and brittle which is what you want for locating because that aids in accuracy when grinding the pins to very precise diameters anyway they are also case-hardened which is something that works well for the grinding aspect but is not good for shear loads. A high-performing alloy steel for that application would be something in the 4340 family or 300M. This is the steel used to make airplane landing gear which is subjected to incredible sheer and fatigue loading over many cycles of the life of the landing gear It could be Cummins went with a high-performing steel such as this. Also I like what you did with the keyway again I'm not crazy about pins for loading in sheer and this is exactly what a keyway is designed to do. And one other thing what is the diameter of the Cummins pin versus the others that could play into it as well So there you go, these are some points for your consideration to help troubleshoot this issue. good luck!
I’ve heard of many Duramaxs breaking cranks after a water pump change. The harmonic balancer needs to be removed and reinstalled. The torque spec for the balancer is 260ft lbs. if that’s not done correctly and it comes loose it’s sheering those pins off. Also. The Duramax firing order starts on cylinder 1 goes to 2 and ends on cylinder 3. It puts a lot of stress/pressure on the snout of the crank. Duramaxs benefit from an alternate fire camshaft.
This guy deserves some kind of award for using social media for a really good cause. I think the common idea that social media has fostered so far is that the pin is a serious defect and a keyway is the fix. From what I think I now understand almost no one knew any better. It appears to me now that these issues aren't from the factory but improper torque. Now if im fos i hope i will be corrected
Not an expert mechanic and didn’t finish my engineering degree either(close but no). However I agree with your observation of “Best use of Social Media for Society” award. However, upon reading many of the replies, the dowel pin is and was NOT intended for providing gear driving but only meant to guide the placement of gear for proper cam/valve timing alignment. This does not mean the pin isn’t subjected to preventable forces exceeding material strength. So yes a full keyway to replace the dowel pin would eliminate this problem but is not cost effective to manufacturing process. Especially when the dowel pin is not meant for driving the gear. According to the majority of replies I’ve read, the excessive forced applied to the pin (causing sheering) is likely due to several factors, mostly design specific factors. i.e., duramax bolt holding dampener being used to press the gear on the crankshaft when torqued properly, or Cummins using tighter tolerances in materials and assembly methods vs. Power Stroke, and straight cut gears vs. helical cut gears, etc. Hope you’ve learned as much as I have🧐
Duramax and Powerstroke are V configuration. Twice the valvetrain movement as the I6 Cummins.
Also the cummins is straight cut gear in comparison to the heli cut gear of the Dmax and Powerstroke. Straight cut gears produce no forward torque
You suck at math if you think 8 is twice as much as 6. Or 32 is twice as many 24.
Okay. Obviously, it is not. My point is that there is more shear force on the valvetrain of a V configuration than an inline configuration. That is why inline motors are far superior in longevity than any V configuration. It is simple geometry. With pushing the valvetrain to opposite angles, you can not deny that the force placed on the camshaft is exponentially higher in a V. But I am stupid, right?
@@danielmattiello4404 Stupid, *maybe not* , but the force exerted on the cam is only 25% more, on a V8 engine, and there isn't an application where the location dowels take the force anyway, the vibration damper *pinches* the timing gear in place, *that* is what holds the gear, the pin only *locates it* it *DOES NOT, and WAS NOT* designed to carry the load. If you left a Cummins damper bolt loose, it would rattle itself loose enough to destroy shit, just like the Duramax, and PSD, been fixing them since they came out, more than 20 years, bud.....
@jamesgeorge4874
Now, what i am talking about. I could care less about the brand. The only thing that matters is the gear cut. Cummins is straight cut. 90° to the crank. All force turned by the crank gear is turned at 90°. There is no walking of the gear.
Now, the PSD and Durmax both have Heli cut crank gears at my best guess of 35- 40°. No matter how hard you try, you can not stop a heli cut gear from walking. No different than a pinion. Hence , they blow through a dowel and not a keyway. Keyway allows walking in the given area and still staying in the line of work. I'm not trying to bust your balls, but I do know what I am talking about. Honestly, if you could put a straight cut gear in a PSD, it most likely would not shear off the dowel. Why do you think all high HP motors run straight cut gears? Less issue with mesh at higher rpm and out of the diesels PSD and Duramax are the highest rpm range.
@@danielmattiello4404you are correct
Industrial mechanic here, if I were to design all three I’d used a half moon or woodruff key with gear being an interference fit; needing heated to put on. I’ve seen a lot of keys and pins sheared in different applications and this is the strongest I’ve seen. My second choice would be a regular key in about 1/4 inch with interference fit but key stock is usually not hard enough to last extremely long times but will give a bit before shearing. Pins are usually hardened which means they are all or none. They’ll just shear with no warning, there is no give.
I'm not a engineer but I'm a old man who has been a mechanic for 40 years now and I have to say that it is the way the gears are cut and it's a angled gear and it's going to apply more force than the straight cut gear. I don't have a technical answer to why the Chevrolet and Ford doesn't have keys and should be headed and pressed on to the Crankshaft. The ones that are on the Ford and Chevrolet engines along with the angle gear cut and the extra pressure with out the keys to hold them with being have to be pressed on and off along with the cost cutting to save a few dollars along with the gear cut on the Ford and Chevrolet Diesel engine. Why would you do something that is not a solid and durable to save the extra effort to machine that key way and pressing on and off of the gears with the angle cut is a good recipe to fail. Your videos are proof of the cost savings for the manufacturing process and then passing it along to the customer that is going to use these trucks for medium duty towing and heavy duty work trucks is not a good recipe for the next purchase of a truck by the customer next time they are going to look at the Dodge diesel for the reliability of it over the others. Both should have been recalled to fix this engineering dept flaw or screw up. Going to be a repeat of the 6.0L in the older Ford truck not only for Ford and the Chevrolet Diesel engine. Hopefully you don't laugh at me too much for my answer 🤔😉
@@lonerider5315 even though I have assembled a changed a ton of motors for my friend's, customer base, and family, I have never been told of anyone of my engine's or transmission jobs fail. Wear out slow and sure as they should but never had issues like that but I have been tacking gears on stuff like that since I was in my early 20's and I learned that from a Old Time Tanker mechanic from WW2 and Korea and it never failed him and he was a great talker of a little bit of insurance never hurt anyone or anything. I would say I love to learn something daily if possible. Good day to you and thank you for the information.
Peter touched on the answer. Rockwell hardness testing of all associated parts would be beneficial.
Closely followed by dowel material
Its all metallurgy, same reason we have camshaft failures in 2024. One material wasnt the right one to use.
Bingo! Big corporations only see numbers, so when it comes to choosing good steel and shit steel for your high stress components they only care about the profit margin. It just has to make the warranty period, then it's your problem.
From what I’ve heard through researching this issue it seems to be when the truck has been worked on and not torqued to spec. When re installing the balancer if it’s not torqued to spec it can take out the dowel pin. The pin is only there for alignment purposes.
Someone with the Real answer 🇺🇸👍
so your implying theyr torquing the cummins to spec and not the duramax ?
why would a large sample size of mechanics do it right on one motor and wrong on the next?
@tx6695 I think what they're saying is the duramax balancer has to come off to do jobs like the water pump, so when it's reassembled the crank bolt isn't tightened to specification allowing the gear to spin and shear the pins. On the other hand, the cummins balancer doesn't come off for the water pump so the bolt is never touched, the torque is never changed, and the pins are just fine. Plus I think the cummins press fit interference is tighter than the duramax.
that makes sense.
i have a 6.0 PS and a 6.7 cummins
lot of crap gets messed with on the way to getting something fixed on the PS.
not on the cummins
@tx6695 i definitely agree with the powerstroke stuff!! The dowel pins are really just there for the alignment of the gear not necessarily to keep the gear from spinning. It's the torque of the crank bolt against the balancer that's 'supposed' to clamp everything together.
Is so nice of you to make these videos for the public thanks , I always like to instruct my self with these types of content’s but I like to instruct my self with with the comments of the communities thank you again Blessings
It's the loading and unloading of the gear on the duramax and it being helical so there's forward thrust also on it , having a pin sideways like that greatly reduces the sheer strength of the pin , had it been pinned like a ls balancer gets pinned for a supercharger and like how the key you guys do is installed it spreads the load an immense amount along the snout and will always be stronger probably by thousands more psi of load capability.
The cummins gear is straight cut that eliminates the thrust right off jump , it's press fit so even if it could move it'd likely gall the snout and lock 1st before the pin ever sees that full load produced.
"This is just a press fit"
Points to giant tack weld
😂😂😂
And That's why they had to tack it...
The weld is aftermarket..It's the fix!!
They added the weld
Huge slug just sitting there 😂
That one what's the Ford not he Cummins.
Lots of good answers. Most are pretty straight forward explanations, not "rocket science". This stimulates me to ask "how did something so easily explained by the public escape the engineers"?
Engineers says it all!!!!!!
NVH Engineers got involved.....
Book smart and possibly no real world experience
@@terriecotham1567 Hey terrie. People have used this "book smart no real world " response for years. It used to be the favorite comeback from guys talking shit about their coworkers that had a diploma full of ASE certs. I would always listen to these guys that had trouble taking tests but I would finally get around to asking one question, That question would be "can't a guy have his ASE's and also have excellent hands on talent"?(of course you could) Having your ASE certs does not mean you are no good hands on.
@@danielrose-tt7os
I was talking about those who have came out of school and never gotten there hands dirty. Yes they can do amazing things on paper with math and computer's
And those with ASE Certified technician's for the most part have some hand on experience.
But many times things come out of the Auto makers and come up short to getting the job done.
Perhaps it seems like a good idea to do away with the key slots and install pins.
And on paper it looks great. But in all truth it's a major weak point.
Those with advanced Eadcation can at times make big advantages in every thing and can also get it wrong.
Just look at some of the engineering in today's car's from engines to the computer control systems and tell me they are that much better. When repair cost are mixed with the cost of the parts.
One of the most advanced things in car's for the cost was the induction of the electric Ignition system. Doing away with the points and ensuring a longer lasting in performance.
When you have to spend 2 to 3 hours just removing things to get to the Vale covers that's not an advance in service
When you run a cooling hose through the middle of an engine and it's possible you have to tear down parts of the engine just to replace a hose that's not advanced
When you make plastic parts like a vale cover or oil pan that can't be reused that's not advanced.
Car's have become High price computers and Software control systems.
Are car's All that advanced if you work as an ASE Certified technician's in any shop hard to believe you think spending an hour just to replace an Oil filter is advanced Eadcation and well engineering
Hard to believe your happy with the lay out of some parts or the time it takes to serve them.
Those with ASE Certified papers hanging on the wall have worked for them and Lear many things others have not.
But at times those with real hands on every day experience who work hard and learn as well at times have a better idea.
I wasn't trying to put down anyone from college just trying to point out how all those in the engineering team came up with a bad idea.
Before even considering any gear loading it appears the Cummins gear has 2 advantages- More surface area to hold the press fit mating the gear to crank and also the I D to tooth root is dimensionally larger maintaining that press fit with more mass to to maintain the press fit as well.
Helical gears have more surface area. The tooth is longer for a given gear width. They are therefore stronger than straight cut gears. They are also quieter running but do have power loss due to the side loads and additional friction caused by the longer tooth form. You pays yur money and you takes yur choice.
I’m only talking about the surface areas of the shaft to gear internal dimension. Gear tooth contact surface area for this discussion has no consequence. But as a random factoid unrelated, you are correct.
I'll take that. I guess it might relate to the machine tolerances of crank and pully as to the maximum and minimum clamping force bandwidth avalible. A minimum tolerance crank and a max tolerance gear might be enough to cause issues.
Ford is crap
The Duramax is obvious. The Cummins has a tighter interference fit. Crap shoot with Ford. You guys do a great job..
Without getting too technical, although I’ve enjoyed reading the technical comments here, I think the answer is obvious. First, the inline 6 engine is arguably the most sound engine there is to offer due to its almost perfect harmonic balance amongst other things, and Cummins, not Dodge, has been producing quality heavy duty engines for decades. Their name is world known and trusted, because they have proven many times over that they know what they’re doing.
would an inline 8 in theory be just as good ? or any even number
@@jchockey22in theory, I would say yes. But it seems the sweet spot is the i6
Inline 6 has better dynamic balance and therefore less stress on the timing gear, also less parasitic load with less cylinders and valves to drive
Torsional damper bolt torque is what holds the gear tight against the crank, pins *locate* the gear, but does not HOLD it.
Nothing technical about it! It’s done purposely to generate work for shops like yours. Plain and simple
Exactly, I was taught years ago the pin or keyway is only there to align not to hold in place. The bolt does the job of holding it all together and if not tight that will transfer the load to the pin or keyway. Also watch out for a bolt that has been over torqued and is bottoming out.
@@philip_james Bingo. I was taught that same thing over 30 years ago, by a veteran diesel mechanic with 30+ years of service and instruction experience, at the time.
So I have a number of thinking out loud questions.
1) what does the duramax, powerstroke and Cummins have to rotate with that gear? Fuel pump, oil pump, cam ect..
2)how many teeth (outer diameter) of the gear is each one? Does this remove some applied stress because the gear is smaller?
3) how fast and hard does the torque come in for the powerstroke or duramax?
4) whats the press fit tolerance for each one? Does having a full length key way help or could you get away with the proper press and small alignment down?
I kind of like this game of asking questions and giving people the opportunity to answer.
The added variable I haven’t seen mentioned yet was; which injection pump is in the system and has it been modified ? What is the required rail pressure, did those bosch pumps fail prior to the crank gear shearing or spinning?
On top of that , the difference between valve-train torque requirements, and straight cut gear vs helical cut gear .
Comes down to a couple different factors for starters the gears them self have a massive difference between surface area on the contact surfaces of the crankshaft second the dura max is a v8 it’ll have more spring tension on the gear from the cam shaft and extra components
The Cummins uses two methods to hold the gear press fit and a pen plus V8s Rev higher and harder then an inline 6 just two possible causes
They all redline 50rpm from each other
The harmonic dampener is not pressed on for Dmax applications. The torque from the fastener clamps the dampener to the oil pump gear. The pin is simply an alignment feature. The pin sees zero torque.
The dampener bolt comes loose (happened in testing), the pin sees torque and sheers. Dampener rotates causing engine misbalance and low/no oil pressure in worst cases.
Straight gears are always more powerful the sideway gears have the ability to have the gear go forward and back therefore less stress on the pin that's why Cummins rule..
Correct, straight cut gears center the gear. They are noisy but do not fail.
What if they’d run the helix the other way as to press the gear into the crank flange? 🤷♂️🙄😅
@@tbthedozer Stuff like that is why herringbone gears are a thing.
I think on the duramax a lot has to do with you need to remove the balancer to change the water pump and people do not torque the balancer when they put it back on.
It’s definitely this! Bunch of yahoos thinking it’s ok to just send it. Torque specs are important for a reason, especially on the higher ends of the spectrum
It would be interesting to see metrics on this theory of who's had their pump changed.
ya cause cummins is just removing belt a couple bolts and you've removed the water pump, never touching anything on the crank.
From my experience it's usually because someone removed the balancer to do a water pump or something and they don't replace the balancer bolt because they are torque to yield bolts and they don't torque it to spec.
That’s a theory, but a buddy of mine had them sheer in 2 different trucks. One at 78k and the other 99k, neither of them had the balancers ever removed. GM wouldn’t honor the warranty
The Cummins pin is halfway in the ⚙️ gear. A Cummins is better balanced. You can't miss with an inline 6.
The cummins engine has alot more torsional twist compared to the other motors. I build all of them.
@@tomroe7715yes more twist on the chassy, but not on the crankshaft itself
I have 255,000 km on my Cummins and the only thing that has broken on it was the F-N Chrysler water pump was leaking .
@@gregcurry1502 And what other manufactures water pumps never leak?
My uncles solution for that is to take a 1/4" drill bit and drill right between the pulley and the crank snout and then Hammer a dowel in the long way.
They actually sell a dowel pin drill kit to do this.
So you drill a hole through, weakening both components and possibly starting a stress crack, then pound a steel pin in the hole, adding additional stress the components weren’t designed for. What could go wrong?
@austinhogan5216
Still... it's an improvement over the stock tiny pin.
But the keyway that put in by Dave's is the best way to go.
The cummins gear has a bore diameter spec of 2.515-2.517in and the crank has a spec of 2.5193-2.5201in. The gear gets heated to 350° for about an hour and installed. All info straight from quickserve
this
Yep this here, once gets hot gear can expand enough it has room for the pin material to fill. The pressed one is so tight there's no where for pin material to go so it holds better. That's aside from that tighter diameter helping to hold it. If you removed all other forces and had only pins but no where for the pin material to go when force is upon them they'd still hold. Of course such a set up is impossible but the physics is more understandable thought of in that way. Kind of how even something soft as oil can hold and push things around when it has nowhere to go, hydraulics work too though.
In addition I should say the keyway fixes it so well because that's a lot more material with a need for far more room to move to in able to shear.
I'm guessing the dowels are just there for timing and not holding the gears. The Cummins gear is more than twice the size of the ohers so the press or interference fit is holding it much more securely with that much more area
Without keyway it will slip everytime. I see it all.
@@tomroe7715So with what I see and that you state the pin needs to be in place my guess would come down to the tempered strength of the dowel pin.
Resistance on the valve train could also be a contributing factor.
@craigtimmons3468 yes sir, usually when I get a new motor or rebuild one, whether it's max, cummins or especially the 6.7 for I put 3 small welds on the cam gear. I just had a brand new rebuild come in from a company in Canada and we didn't tack the gear. Well it turned. The motor was sent back blowing air out the two intakes. If I could send video I would. BTW 36 yr master cert ford and chevy tech.
@craigtimmons3468 consider when a gear is pressed on, it will distort a small amount no matter how careful you are. The heating process and yes torsional from valvetrain do the rest. Tacks are mandatory.
The torque spec for the Duramax balancer bolt is 278ftlbs. It has to be removed to replace the water pump.
So please be patient with me . The other year I replaced my water pump on my 08 Duramax and it took me a long time cause of my many back injuries. I only learned about the shearing off of the pin and it’s better to install a key way . Can that be done wo pulling the engine and just removing the grill , radiator and water pump ??
@@eddiereyna2998 My point was that the problem will occur if you didn't apply the correct torque. Retorque it if you are concerned. To answer your question, yes you have to completely disassemble the engine to get the crankshaft machined.
@@davidmitchell7183 thanks for the response .
Tis will be sometime before I can save to get this taken care of.
I just recently paid over $5,000 for a new CP3 pump and some injectors and glow plugs but the truck would still go into limp mode . After the 2nd time of taking it back it did it again .
Now I’m on bed rest for 6 weeks from a surgery. Oh well , let’s see how the world turns .
I appreciate your input .
@@eddiereyna2998Take care of yourself before the truck.. Find somebody local that is good at diagnostics. In my experience, I saw quite a few rubbing wiring harnesses and electrical gremlins.
@@davidmitchell7183a Chevy with electrical problems... no way! Lol. I say this because I've driven (never owned) many a Chevy as an hvac tech and every last one of them that I had for any length of time had an electrical issue. One problem child left me on the side of the road three times before the problem was fixed. Bad spot in the crank pos sensor wiring.
Many correct answers here. The pin is there to position the gear's angular relation to the crank. The difference HAS to be in the adequacy of the shrink fit. The Cummins is thicker between the ID and the valley between the gear teeth. More metal means more pounds of tension even with the same shrink.
Torque is the enemy. The only way to spread the load evenly from a torque aspect is more main bearing surface area. An inline engine inherently spreads the load service across the mains because there are more of them. If you can spread the torque load across the entire engine you’re eliminating the moment of inertia on the crank snout/gear.
Mech-E here. I would say you are dealing with difference in torsional vibrations between a V8 and an in-line 6. There is a reason you don’t see over the road trucks with V engines. In-line configuration are producing a sine wave vibration on one plane rather than 2. There is still a lot we don’t understand but we can measure it with problems like dowel pin shearing or crank failures.
Also, someone said it earlier but helix cut gears provide a bit of forward torque where square cut do not. Trade off it noise.
I was thinking the straight cut gears efficiency verses the heli gears quiet. Cummings are for stump pulling and Duramax are for getting groceries. The Ford is in between.
Please explain in engineering terms what "forward torque" is. I am also a Mech-E and I'm unfamiliar with WTF that is.
Perhaps you meant to say the helical-cut gear is subject to an axial thrust when being spun??
Detroit had 2stroke diesel v6, v8 ,v12, & v16 in OTR trucks for decades
@@jarvislarson6864 The point?
There are thousands of V configurations out there, dozers, big loaders and graders, haul trucks, power generators, locomotives and excavators. Road tractors don’t have V-configurations anymore because they wouldn’t fit under the hood. The V engines put out way more power too. No other reason.
Hi, In my humble opinion, Cummins are one of the best engineered engines ever built. I’m sat above a 25 year old M11 in an English made ERF (1999 model) it still runs perfectly after a million miles! The stress that goes through a drive train like that requires a very very tight interference fit with a woodruff key to align it. Better still is a taper fit drive with a woodruff key which never ever fails if assembled properly. It’s all down to the cost of production. I’ve never worked on one as we don’t have them in Britain but it seems to me that Duramax is made to a cheap budget and that design is always asking for trouble! Thanks
Cummins are simply GREAT engines if maintained correctly . A straight 6 Engine is naturally balanced - Phyics . My father told me about Straight 8's :" They were so smooth " .ROBBIE - Australia 😊
The V8s should in theory be more robust since they're doing more firing pulses in each revolution, so torsional pulses and valve train loading wlil be less pronounced.
An informed answer would require a rockwell test of all cranks, pins and gears.
Took the words outta my mouth, man!
A soft pin or hard pin aint gonna help of the crankshaft slot/keyway is poorly fitted.
Hard crank, hard pin, would maybe 100% solve the issues, except IF it slipped the crank AND the resr of the shaft (giggity) is ruined.
What all runs off that gear? Fuel injection pump? Only timing? Both?
I'm more gasoline or nitro type of dude, but pressfit unless it's a temp differential plus like 0.003" interference fit, freeze shaft, induct heat gear, press on, etc that might work for pure stock stuff......
How much lubricant is moving around in these various drive scenarios? Not enough or too thin a oil/oiling system would stress that crank snout and gear pretty dang fast.
But hardness tests first. Even some hazard frought files just to get a idea what the relative hardnesses are.
Then magnaflux, cuz could be fine on metallurgy but have manifacturing impurities and tiny tiny cracks.
If I had a wasted crank in my garage I'd go full cut off wheels and torches, cut it up, sand and polish, stare at magnified sample bits of metal and deduce something.
Most likely some sort of hardness and oiling/lack of oiling, car gods hate you and want you punished... Normal shit😂
@threadtapwhisperer5136 I'm gonna go with "angered the car gods". They obviously didn't burn the correct incense or anointed it with blessed oils that you have sworn at/bargained with/begged to work
Pins are designed to shear, to protect the more expensive parts. Keys and pins, could all be made out of better materials.
Cummins runs tighter tolerances on there press fits, and made to higher standards along with better quality
That was my first thought too. @g1channel found the specs (precise!, if manufacturing can consistently do it), and Cummins heats up the gear before putting it on, not sure if the others do, could by they have to as well. Also, metallurgy, surface hardness variables.
simply if it doesn't break you do not need to buy replacement engine called built in obsolescent
I'm not sure if they're made of differently tempered metals, or Chinese vs. Canadian steel, but that could certainly have an effect. The width certainly has an effect in a press fitting, but the Cummins needs the width because it has so much torque. The inline 6 is better balanced, which means less impulse would be felt by the dowel pin, which I have effectively seen mentioned.
Id have to assume that the press fit is tighter, so the dowl is purely for alignment. Gear is probably dropped on hot then dropped on like a press fit bearing is installed without a press, so they don't spin or walk back off wonce in place. Thanks Dave.
The Cummins has straight cut gears and the the other two are heli-cut, I believe is the correct term.
Finally someone said it. I'm sure the balance of the inline 6 has some effect on the dowel pin breaking, but the main culprit is that right there. There's no diagonal load on that straight cut gear, only single dimensional.
@@helixleviathan2620& would induce a however minor.. drive torque bending load harmonic
No they are all straight. Torsional forces are the enemy, brand doesn't matter. Helical are never used in this application because of torsional forces that would require special bearings to keep both shafts centered.
@@tomroe7715 look again
@@tomroe7715 look again
Cummins uses press fit and the pin when ford only press fits and duramax only uses the pin. I believe that is why it happens. Also cummins is a inline 6 and dont rev as high as V8’s do. With 2 extra cylinders and higher revs, its more stress on the gear and helps cause the failure
the durmax will runaway from the cummins when i was in the army 2 knuckle heads in my shop bought diesel pickups even thought they didnt need it after deployment, both 3rd gens because thats what they could afford in 2014 the duramax smoked the cummins both had chips and a down pipe. cummins might tow better an last longer but 8 holes lighting the fires is definitely faster
There's no way the Dmax relies solely on the pin to hold the gear in place...
Calm and knowledgeable NO DRAMA style of speaking. Your dad can learn from you.
My 7.3 power stroke has 482000 miles. Still good
Don't see this problem on the old IDIs either.
What does that have to do with what he asked?
Because Cummings is it's own company. It's building just engines.
It's Cummins. No "G" in the name. Duramax only builds engines also
Duramax is Isuzu @@countcuda70
@@countcuda70Durammax is Isuzu. Isuzu builds all kinds of stuff. Trucks, Buses, Suvs, Cars...
@@akabruno1 Duramax isn't Isuzu. GM and Isuzu partnered together in 1997 and created Dmax LTD. All 6.6L Duramax engines have been built there. Isuzu never made the Duramax. It was a new build when it was introduced. All 3 manufacturers had help with their engines. Cummins and Case. Ford and AVL.. What's the issue??
Straight cut gears don’t create side loading therefore fewer forces on the dowel pin
Electrician/racecar mechanic here. The harmonics created from the V8 configuration create stress on the crank. I6 is smooth when it's not breathing engine farts.
Straight six has a more distributed load and more balanced, maybe. The V motors might have a mixture of high vibration and torque load not being linear.
Inline6's have more harmonic issues with crank whip.. ALL straight 6s.. the short V engines cranks dont
@Errol.C-nz well at least I tried to think lol. I was wrong.
One thing that I have noticed is when you turn these trucks off, you hear a loud screech, which is the belts and all of the front end accessories still spinning for a fraction of a second after the crank comes to a halt. That is quite a bit of rotating mass coming to an instant stop. With the tension that is on these belts, I believe this has a lot to do with shearing off the dowel pins.
working the balancer back and forth.
I was once running a cup car engine on an electric transient dyno. The exhaust temp failsafe had been mis-programmed to initiate a "hard stop" rather than a "cooloff run", meaning once the EGT hit the limit, the dyno controller cut fuel, cut spark, and applied FULL dyno braking. That engine went from 9200rpm to 0rpm in one half a crank revolution, according to the datalog.
Before running the engine again, we checked valve lash and ensured the cam degreeing was still correct - it was. Engine ran like a champ afterwards. Zero damage, much to our surprise.
Engine had a belt-driven cam; dunno if that made any difference.
Inline engines close to being perfectly balanced and from experience I have found V engines to have much higher vibration. I also believe on the Cummins the dowel pin is for alignment, not retention.
Right now I drive a medium duty vehicle with a Navistar VT 365 engine and I will admit it resists spooling up partly because of it's V-8 configuration....but in the past I've use 5.9 and 6.7 Cummins and they very readily spooled up in indicating much less torsional stress.
The Cummins has a bigger diameter crankshaft which has a larger frictional area for the gear. The press fit may be slightly tighter on the Cummins.
Yeah, the Dmax has a tiny snout, and more valves to open, and revs higher. Not a good recipe for the gear staying in place.
Maybe because duramax rev higher and people that drive them have heavier foots.
Heavier feet 😂
@@mahmoudsankari3842*footies 🚼
Never seen a powerstroke weld break in the gear
They're not welded from the factory. The shop welded it
the press fit of the cummins is actually absorbing most of the load placed on the gear. the pin is merely for alignment/timing purposes
the duramax is shearing the pins of during a deceleration cycle due to the compression loads placed on the upper half of the engine and fuel system
Working in construction, I have noted steel hardness varies from area to area in the continuous 48 states. I have also noticed that older steel is much much harder than new steel, I assume the mines used then were from the US vs foreign
I feel like the type of metal used and quality of the metal used plays a big factor to that problem.
You would be wrong.
This Q should be on the other channel bigger reach
Material composition. Heat expands and contracts as we all know but the material for these 2 products are from 2 different companies that use different iron makeups from China/Argentina/Mexico etc. well when it's under pressure and friction occurs the dial pin within the 1/16th of gap friction occurs and completely gives way.
I also agree with straight cut gears vs helix cut. I would also add that Cummins gear has full width gear vs half cut gear of the others there by spreading the torque load to the entire width vs have gear causing more torque in that area hence it’s basically a lever.
Perhaps the pins need to be a higher grade and/or a larger diameter.
Cummins has experienced with semi engines. So they make their small engines using the same tried and true methods as their larger industrial engines. My Cat c15 had a the same setup as the Cummins.
I had this problem with certain engines when I was rebuilding them I either put a bigger pin in them or I just cut a keyway in them.
I worked for dodge when they were having issues with the nut that held 5th together on the 5 speed backing off. My understanding is ford who used the same trans didn't. It came down to harmonics. The 6 cylinder had a different frequency than the 8 so the nut came loose. I wouldn't be surprised if the same thing was happening.
If v 8 Diesel is so good why don't you see them in farm tractors and big trucks !
Width.
@@mantisushiwinner winner chicken dinner. There are plenty of big truck V8s running around Europe. Scania seems to be the most popular.
CAT has a V8 V12 and V16. It's all about clearance and materials. If you go cheap on materials like Chevy and Ford you get what you pay for. You upgrade everything to high end shit you get better results.
You do in that European brand famous for there V8's too lazy to look up the name starts with a S.
Serviceability is trash, and also its simpler to in line. Simple means space. Space is Serviceability. Space is cooling. Space is auxiliary modules. Space is more turbo, more Radiator. Vertical engines also see less wear and oiling issues. The more flat you make it, the higher your woes with oil and uneven wear.
On the cummins the gear is a press fit and the pin holds it from sliding side-to-side.
On the Duramax the gear is a loose fit and the pin holds the gear from rotating along the rotating axis. This pin is subject to various load stresses, as engine speed, horsepower and load are transferred to the "holding pin".
Harmonics , inline 6 engines inherently have better balancing hence less crankshaft harmonics . Idk I’m just guessing I’m by no means an engineer lol.
You never see 18 wheelers having v8 diesels powerstroke and duramax aren’t real diesel motors
@@wm2086 yeah the duramax isn’t a “real” diesel. It’s not like they are the engine of choice for thousands of military combat vehicles like the armored Bear Cat.
Those engines see combat but of course there’s always a butt hurt Cummins fan boy around somewhere
@wm2086 yeah semis do. 3408, 8/12/v71/92 most European one's are a v and north of 700 hp
@@bondobilly9369 not as common
@@wm2086 500 Mack V-8.
I haven't worked on these series of GM or Ford diesel, but a hell of a lot of the earlier series. But do work on a lot of Cummins and Dietroit. Factory trained cummins, detroit, cat, allision, voith, and ZF.
The Cuminns harmonic balancer, when bolted up, does not use clamping force against the gear. It is a flange to the front of the crank. The gear is heated to about 290 deg and pressed on.
Both of the other engines discussed do use clamping force to secure both the balancer and timing gear to the crank. I would bet that the bolts are being reused.
Detroit diesel on most of their inlines, series 50 and 60, specify new bolts on the front and back, IE: harmonic balancer and flywheel or flex plate.
Also most manufactures specify a hour or mileage for harmonic balancer repladement. There is a reason for this. The balancer is a "harmonics" balancer. The outer and inner are pressed fit over a medium that allows torsionaly movement. Some are part of the actual balance of the interanal rotating mass. When the mass as a whole is not in balance it can cause bolts to be stressed and cause stretching which of curse causes the clamping force to weaken.
I have seen long drive shafts in coaches that are out of balance ruin rear planeteries in automatic transmissions.
In manual trans they will wipe out thrust bearings and harmonic balancers. Cummins has literature on it.
I have discussed these issues with the Western US engineering tech for fault analysis from cummins.
The cummins gears are a really tight interference fit. Once its on theres a special tool from cummins to drill into it till it relaxes. It was a common thing on the isx family, but the b,c and L series are similar
Because some engineers thought he would try to quiet down the crank gear... Think about it...
I have a strong feeling the Duramax crank shafts are manufactured in another country whose name begins with the letter “C”.
Duramax has never been made in China. Good try. It's built in Moraine Ohio. The refinery is in Defiance Ohio. Nice try. Powerstroke is built in Mexico. All Cummins powered Stellantis trucks are too...
No yahoos dont torque the balancer back to 278ft lbs and it gets loose
@countcuda70
Pretty sure he mentioned the "crank" not where the engine was built.
The reason is the difference in how the gears are cut, just as many have mentioned prior to my comment. Straight cut gears have no vertical torque placed on it, so it stays in place. the helical gears have vertical torque due to the design of the gear, so over time you will see the gear start to walk, and eventually come loose.
The fix is to convert the Dmax and Pstroke to straight cut gears (if possible), or do a key install or weld it in place. Straight cut gears are far superior to helical gears.
Part of that may be attributable to the loads of V engines valvetrains and also possibly attributed to the type of harmonic damper being used as well...for those who thinks inline sixes are just better, I remember the days before Houdaille viscous dampers were adopted and installed, (by Cummins & other manufacturers), big inline diesels would snap crankshafts right behind the #1 rod throw...yes, I'm that old and have that much experience...
I'm here for the comments. Hopefully, there is a follow-up with all the engineering explained.
Inline 6 vs v8.
I'm a Materials Scientist and I would suggest the reason for employing different methods of limiting gear damage is to use such ways. But the reason is the manufacturers have tested the components to failure and know how much is the safety margin. Engines are built to a cost and to minimise costs cheaper methods of assembly are used Undoubtedly the long keyway is the strongest most expensive method.
I'm no Automotive Engineer but my answer is based on my work on understanding steel and its composition and heat treatment. I worked at JN Kirby Products Rockdale Sydney Australia. I certified Materials to specification for car parts and assembled units for car manufacturers.
Personally I think it happens during engine shut off when the compression causes the motor to run backwards for a second and then snap back forwards the old 12 valve Cummins makes the belt squeak it happens so hard so if that's what's going on I would understand why
Cummins doesn’t have enough power to shear it off 😂😂
😂😂 LMFAO😂😂 TOUCHÉ!
Cummins is OG they know what it takes to make reliable power
The straight cut gears on the cummins will put less torsional force on the pin thus limiting distortion on the gear body and increasing force on the pin with load changes. Straight cut gears are louder and will steal more power but can transfer more power assuming proper gear meshing.
To give a thoughtful answer we need to know the pressure of the press fit or at least the interface of the fit. (0.001" =7 tons/inch of shaft in mild steel). The Cummins gear has a consistent pressure width due to the design whereas the other gears do not. Personally I would never install any of those gears without the appropriate loctite.
Fits and vibration are contributors but the helical cut naturally tries to push and pull the gear out of place if nothing else it fatigues the pin. It would be interesting to see the pin shear in relationship to rotation direction.
Mr satellite
Is right on the money with the heli gear it's basic physics
I'm at 350,000 miles after a pressure relief valve issue, and new melling at 278,000 miles same pins in crank and torqued it to spec. By degrees and it is still holding
I am a engineer for non automotive machines. I can see a major problem with the gm/Ford gear design. First, straight cut gears are stronger than helical cut gears with the drawback of being noisier. Second, the gm,Ford gears are almost half the width of the Cummins. More surface area on the thrust surface to spread out the load.
The industrial equipment almost exclusively use straight cut gears in load carrying drives.
Look at the shaft diameter where you mount the key way or pins. Larger diameter means lower shear forces.
I would say it probably had sumthing to do the the Helical cut gears, and/or shorter crankshaft, but being shorter might not matter just depends on the thickness of the journal size and robustness of the crank and how hard each power stroke hamners that gear and how that gear loading affects the fit to the crank
Would be interesting to know how many of the engines that experience this failure have had the balancer bolt removed and reinstalled for service vs undisturbed. If the majority are undisturbed, it might be due to crank harmonics from the V8 vs I6. Simply retorquing the crank balancer bolt periodically should prevent the failure. Those dowel pins and shrink/press fits were not designed to take the full torsional load from the valvetrain. The design has no failure tolerance for inadequate clamping from the balancer.
My guess would be people aren’t torquing bolt after reinstalling it. The pins are for alignment only the balancer is press fit and is held by the bolt. So, it could be a factory issue too, not getting them tight. Just my two cents.
When you combine the helical cut of the gears instead of straight cut like on the Cummings plus you add the press fit of the Cummings versus a non-press fit of the Power Stroke and Duramax. There’s the two reasons right there… 100%!
I am an engine builder and an engineer, and I have methods to even include more power than what you folks and Gale Banks are doing/making!
Best regards; Edward Heath - engineer at: “new ideas and innovations, LLC“ out of Madison, Connecticut, USA
Type of forces induced due to gear cut angle and the amount of force applied to the gear during operation
Material used in making the dowel pin. Positioning of the pin under the gear. Depth and tolerances between the dowel pin and the slot it's seated in. Gear ratio differences between each gear.
Most people probably dont get the correct backlash in the helical gears. Because its a chore to measure but super critical with helical gears
The lash can’t be adjusted, so proper manufacturing is critical. If you introduce harmonic vibrations by modifying the valvetrain(stiffer springs, bigger valves, etc) or raising rpms above design limits, the force of those loads can destroy the gears quickly. Caterpillar added counter weights to their C-15/16 cams because the vibrations got so bad when cam driven fuel injector pressures went well beyond 10K psi.
Another example is a Coyote V-8. The oil pump is fine at stock rpm. Raise the limiter and you might as well start an office pool for how long it will last before the oil pump gear shatters. Harmonics can be very powerful, and sneaky.
Straight cut gear causes the gear ratio change as it spins from tooth engagement at start to middle to un engagement! Plus and more backlash and less forces and contact time of the amount of torque into gear on crank
I believe the metallurgy of the gears vs. the crank are different enough that its loosening when hot. This causes the gear to smack the dowels from side to side causing the shear. Full length keyways are superior.
You spoke of press fit, is the pin being used predominantly as a install/index guide or as an anti-rotation device. It performs both, but must be sized/designed appropriately to perform as an anti-rotation device based primarily on torque drive required, interference fit and vibration environment.
First off, the name: Cummins are known for great R&D. While many are saying the harmonics and internal stressing of V configuration. Helical cut gearing puts undue stress by the gearing can not equate because of the centering effect if the driven gearing. Cummins inline is just a better design.
Besides increasing the interference fit. I would also look which way the gears are cut straight. Cut gears are easier to turn than angled gears
Take a micrometer and mic the contact areas of where the gears sit on the shaft, it should be a size for size fit or a tight bore and a nominal shaft. If it’s loose it will allow for play and can shear the pin acting as a key. Just my thoughts on that
When I did engines, the springs on the head would set up a resonate causing the cam to resonate twisting the gears!
Two reasons I can think of. One the inline configuration of the Cummins has less harmonic vibration. The second reason I believe is because the front gear is not only pressed on but it also has the dowel pins. I believe if they were to press the gear onto the Duramax along with the dowel pins it would eliminate the problem for the Duramax and if they added pins for the powerstroke along with the pressed on gear it would strengthen it as well.
In addition to my above comment I would say that using keyways from the manufacturer would also eliminate the problem
It's because manufacturers doesn't care about biulding quality
Cummins dow pin is a locator pin used as a stop if the gear spins as its tighter on the crank. Chevy and Ford gears put a constant load on an undersized pin with a gear that can slip due to looser tolerances.
Well right off the bat there may be an application issue because dowel pins are primarily used for locating and not for handling High Shear loads.
Take a look at the cross section of a sheared dowel pin and you will see that typically it's grainy and it cracks and this is the result of being very hard and brittle which is what you want for locating because that aids in accuracy when grinding the pins to very precise diameters anyway they are also case-hardened which is something that works well for the grinding aspect but is not good for shear loads.
A high-performing alloy steel for that application would be something in the 4340 family or 300M.
This is the steel used to make airplane landing gear which is subjected to incredible sheer and fatigue loading over many cycles of the life of the landing gear
It could be Cummins went with a high-performing steel such as this.
Also I like what you did with the keyway again I'm not crazy about pins for loading in sheer and this is exactly what a keyway is designed to do.
And one other thing what is the diameter of the Cummins pin versus the others that could play into it as well
So there you go, these are some points for your consideration to help troubleshoot this issue.
good luck!
I’ve heard of many Duramaxs breaking cranks after a water pump change. The harmonic balancer needs to be removed and reinstalled. The torque spec for the balancer is 260ft lbs. if that’s not done correctly and it comes loose it’s sheering those pins off. Also. The Duramax firing order starts on cylinder 1 goes to 2 and ends on cylinder 3. It puts a lot of stress/pressure on the snout of the crank. Duramaxs benefit from an alternate fire camshaft.
This guy deserves some kind of award for using social media for a really good cause. I think the common idea that social media has fostered so far is that the pin is a serious defect and a keyway is the fix.
From what I think I now understand almost no one knew any better. It appears to me now that these issues aren't from the factory but improper torque. Now if im fos i hope i will be corrected
Not an expert mechanic and didn’t finish my engineering degree either(close but no). However I agree with your observation of “Best use of Social Media for Society” award.
However, upon reading many of the replies, the dowel pin is and was NOT intended for providing gear driving but only meant to guide the placement of gear for proper cam/valve timing alignment. This does not mean the pin isn’t subjected to preventable forces exceeding material strength. So yes a full keyway to replace the dowel pin would eliminate this problem but is not cost effective to manufacturing process. Especially when the dowel pin is not meant for driving the gear.
According to the majority of replies I’ve read, the excessive forced applied to the pin (causing sheering) is likely due to several factors, mostly design specific factors. i.e., duramax bolt holding dampener being used to press the gear on the crankshaft when torqued properly, or Cummins using tighter tolerances in materials and assembly methods vs. Power Stroke, and straight cut gears vs. helical cut gears, etc.
Hope you’ve learned as much as I have🧐