GM TH350 Rebuild PT7 - Valve Body Installation and Conclusion (Please read description)
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- Опубліковано 12 вер 2024
- I install the valve body and finish up the build.
Note: I installed the filter in the incorrect orientation by mistake and have removed that portion of the video as of 10.12.23 to avoid viewer confusion.
It was corrected before that trans went out the door however want to make sure it's not visible here. I'll add back in footage to show the correct orientation or publish an additional video to show that part of the process.
Came across your videos and just like good videos I could not stop watching. I am currently rebuilding a TH350 early version and watching your videos helped me correct a few fitment problems I had. I started with your C6 rebuild earlier this morning watched it all the way to completion it is my next project. Just keep putting them out there you are a very imformative teacher.
Thank you, David!
Good series. Keep 'em coming.
Thanks Skutahuniai, will do.
Great job thanks for the great details
Good morning. I love your videos! I have rebuilt my TH350 and have some experience with installing transmissions. I have a question about bolting the torque converter to the flexplate.... Since the torque converter sags ever so slightly from its own weight when resting in the transmission, prior to bolting to the flexplate,, should you lift it up ever so slightly (take the weight off) as you tighten the first torque converter to flexplate bolt? Or just pull it forward and bolt up without lifting on it?
Hello again. I am desperate for help on something. I finished the TH350 stock rebuild without installing a shift kit. I installed all new clutches, steels, all bushings replaced, Torrington bearings cleaned and inspected, torque converter properly set into the pump (with slightly less than 1/8th inch flywheel to torque converter clearances, all new gaskets (valve body gaskets correct for stock separator plate), all hard parts closely inspected, and complete valve body disassembly, cleaning and correctly reassembled, and final endplay at .024 with a dial indicator.
Prior to final assembly, both forward and direct drum clutches positively applied and held during bench pump/drums clutches air pressure checks. I used a dial indicator to check the clutch pack clearances during air checks and got .032 on the forward, and .048 on the direct drum (stock 4 clutch set up and after installing a .090 steel). Air checked low reverse piston as well and got good apply pressure with no leaks and a solid thud) This is my third TH350 rebuild in the last few years, so I have some experience with rebuilding them. I have also successfully rebuilt a 700R4.
So here is my issue. For some reason I have zero main line pressure with a pressure tester installed. When I initially started it up, I had good line pressure in park, but the moment I started to shift it through the gears, line pressure instantly dropped to zero in all gears. It appeared to suck up most of the fluid in the pan before I shut it off. then when I added more fluid I got no line pressure and no cooler line flow. I have now started it up about 5 times letting it run for 10 seconds at a time and it will not take up any fluid and the pressure remains Zero in all gears and Park. The transmission was in good running shape prior to disassembly, and I was just rebuilding it because it had 130K miles on it. The only thing I did was install some new pump gears (same exact size as the ones that came out. I double and triple checked the gears with a Mic, and both old and new were .725's. I also am sure I installed them correctly. Could I have somehow broken off the torque converter gear tangs? I decided to pull the torque converter loose from the flywheel and it spins freely with no grinding or any other odd sounds. Any ideas of what is going on here?
Damn, sorry to hear JT...Unfortunately, you stripped the engagement lugs off the pump gears upon installation. At some point between when you fully installed the converter onto the input shaft/pump stator splines and when you married the engine/trans, the converter slipped forward slightly, rotor no longer fully engaged by the converter and you didn't notice. It's the most common installation issue associated with these and similar transmissions.
Hopefully it didn't do too much damage such that the working surfaces and gear pocket can be cleaned up on a lathe & mill at the machine shop.
@@nickstransmissions hmm. I don't think that happened because it was fully seated and tied back right up until the bellhousing was about an inch from the block (I always do this when installing a tranny so the converter doesnt move or hang on its own weight. The second observation is that the transmission cinched right up on the dowls to the block with no effort. Then, after the tranny was all bolted up, I still had my 1/8th clearance between the TC and flex plate and it spun freely with this clearance prior to me finally bolting it to the flex plate. So I am not sure how that could happen. further thoughts?
Pull it out and take a look. Let me know what you find…
I re-read this again and, if I understand you correctly, you are saying thst the converter mounting pads where the bolts go were initially an inch away from the flexplate?
If so, that’s the problem. You need to shim your converter to flexplate junction.
Let me know if I am interpreting what you’re saying above correctly as ive had a few beers since, haha.
@@nickstransmissions no, 1/8th of an inch, proper spec
Hey Nick. 2 questions. Is there any way to identify a th350 vs. th350c torque converter? Secondly, is there any way I can email you or send you a few pics/messages?
Hi SuperiorPeninsula - TH350C converters have a much smaller input shaft pilot diameter at the bottom of the converter compared to the standard TH350s...I don't have any way to receive pics but if you have addl questions, you can ask them here...This way, other viewers can benefit from the exchange.
Hey Nick. Are there any issues with building the trans dry and letting it sit? I'll use the assemblee goo like you said and WD40. I don't know when this will actually get put into service. Just trying to figure out if i need to soak and add fluid while building or if it can sit dry. Great videos man. Thank you for the help.
Hey Josh, no issues - just build it dry and keep it out of the elements...My TH475, featured in a rebuild series on the channel, is sitting in a closet in one of my spare bedrooms - who knows when it will ever see a vehicle, lol.
@@nickstransmissionsjust wanted to say thanks again for the videos. I put the fully manual th350 in a 92 S10 behind a 355. I have about 150 miles on the truck and took my buddy for a ride that I bought the trans off of when be broke 2nd gear. He said It felt like it used to in his C10. With 3.42 rear end the S10 will chirp 3rd gear lol. I'm now getting ready to build a rear end before to stocker pukes.
Outstanding
Thanks again, Jordan!
Hi, I sent this final bit of info in the reply below, but wanted to also copy it as a new message in case you arent able to get to all your replies. Also, so I have read a million times how the gears need to be oriented with the dot up, which I did on the smaller pump gear,.. but neither the stock original larger (outer) gear or the outer gear from the new set I bought seem to have any sort of dot to tell which way goes up.. So how do i know which way is up on the outer gear? or does the orientation not matter if it is not marked? and to recap what happened so you dont have to re-read everything is as follows. I had completely rebuilt the transmission, all new bushings and a complete rebuild kit. Went through the valve body and of course new valve body gaskets which i double checked to ensure they were the right ones. Also a new torque converter (with 1/8th gap to new flexplate) and installed new filter. Fired it up for the first time and it had good pressure in park, , then shifted to neural and drive and after that no pressure from main line port or cooler lines no matter how many times I started it up (started the engine and tried to get it to draw fluid on 5 occasions with 15 second run time intervals. dropped the pan and it was completely full of clean fluid, no clogged filter and filter gasket new as well. like I said above, TC tangs on pump gears are still perfect, TC is perfect, and pump pocket is perfect and was full of fluid when I broke the halves apart. So why no pressure after I shifted it to netural drive? One last thing to note is that when I first started it up I let it run in park for about 20 seconds where it had proper presure until I moved it to netural. Also checked the S-hook on the shifter assembly and it is still connected to the valve body. Thoughts before I put it back together? bad torque converter? its new remanufactured. BTW, you have been so helpful, and I am subscribing to your channel today..
Hmmm...What I thought was a straightforward explanation has turned into a bit of a mystery. Glad the pump is in good shape as those pumps are getting harder to find and not all machine shops can recondition the pump body as it requires a specific program to be run on a mill to deal with the crescent. You can buy aftermarket pump bodies for about $100 or so from Transstar if necessary.
Anyway, check out my TH350 rebuild video where I discuss the orientation as I'm assembling the pump and show how the engagement lugs are offset on the drive gear: ua-cam.com/video/5XC99iM4eQU/v-deo.html
And thank you for the subscription!
I'll add that when you put it back in but before you bolt the converter to the flexplate, spin the converter a whole bunch of times. After several turns, you should see fluid coming out of the cooler line fittings...It won't pour out but fluid will definitely flow...If nothing comes out after 10-15 turns then there's either no engagement between pump and converter or something is wrong with that pump.
@@nickstransmissions thank you so much, I will do that. can a bad TC cause sudden loss of pressure like what has happened here?
You're welcome. I don't believe the TqConverter itself would cause low/no line pressure as it just spins the pump, which creates the pressure. I'd install the converter when the trans is on the bench fully assembled and spin it to see if you get fluid. If fluid comes out then I'd check the boost/pressure regulator valve train for freedom of movement just to rule it in or out.
How many quarts of fluid did you put into the transmission total? The system takes between 10-12 quarts including the converter...
@@nickstransmissions well, on initial startup I put about 2.5 to 3 quarts or so in the converter, and filled the pan with four quarts. When I started it up, it took up about 2 quarts from the pan, then no pressure when I started moving through the gears. Then I immediately stoppped it, added fluid to the pan to fill it to the full mark cold, and it simply would not take up any more fluid. I started it up and let it run for 15-20 seconds, but it would not take up fluid or build pressure. I tried this 15 second start and run situation about 6 times with no pressure. Thats when I contacted you and pulled the tranny. I clearly had pressure for about 30 or more seconds on initial startup because my main line pressure port gave me plenty of pressure (I think about 60 lbs, but I only got a quick glance before it dropped to zero), until shifted to drive when it went to zero. Also during these short startup attempts I had a cooler line disconnected to see if there was flow. There was not any fluid. But when I dissassembled the transmission the lines were full of fluid and the converter was completely full. So i did deffinately have line pressure initially. I will try the bench test you suggested to see if I get fluid out the cooling line port when spinning the converter. I double and triple checked the pump housing, gears, and TC and saw no damage, and plenty of fluid in the pump.
So now that it is all running thanks to you help, can you tell me what line pressures I should have under what testing conditions? I cant seem to find this info anywhere, and what I did find was just confusing and lacked enough detail to perform the tests correctly.. TH350 stock build with stock converter, no shift kit... any simple info you can provide me is appreciated.. I did subscribe to your channel... Thanks man!
Glad to hear it's back on the road...At idle, P/N/D should be between 50-70 psi, R should be ~110-125ish and manual 2/1 should be ~150-180ish...You can Google the pressures at stall if you do a stall test but not necessary if everything's working as it should.
@@nickstransmissions Ok, what caused me confusion with the stuff I read online was just a bunch of confusing info on different readings at Idle, then different readings at 1000-1200 RPM, then different at stall, then a different set of pressures if modulator is connected vs. disconnected... etc.. Total confusion!. So just to be clear, you are telling me to look for the pressure readings you suggested at idle with modulator connected (Brakes applied and not moving, correct)? If so, my pressures at 850 RPM (park idle speed) ,with the brakes applied and modulator connected ended up being 70psi in P, N,D, 125 in Reverse, and 110 in L1/L2. (not 150-180 as you suggested) Thanks for just clarifying the testing conditions for me and if 110 is ok for L1/2
110 psi is fine at idle, for M2/M1 - I was thinking of those pressures at stall when I replied earlier.
@@nickstransmissions Oh, ok, so I need to check for the pressures you originally suggested at stall? Or at Idle? I really hope others are reading this since checking pressures is a very common question I see on the internet with no clear answers...
At idle. Stall should be ~3x idle while in Drive.
TY for the thorough information. Maybe you could give me some direction: I had my 1977 TH 350 rebuilt and have noticed that there is an intermittent shift issue 2nd to 3rd that happens when it gets warmed up. I’v changed the vacuum modulator and installed a new steel line from the manifold to the modulator, removed the modulator valve and it seems good. Any suggestions? Thanks
Hi Matt, thank you for the feedback...When you say 'intermittent' shift issue, please describe what's actually happening once the trans gets to operating temp. Based on that, I will likely know the source of the problem. I could guess but don't want to send you on a wild goose chase...
@@nickstransmissions driving 20-25 minutes, after stopping at a traffic light or stop sign the 1st-2nd shift is good, but there is a delay from 2nd-3rd (high rpm’s) or sometimes a down shift once it’s in 3rd to 2nd and it doesn’t happen all the time-the dreaded intermittent problem. I’m wondering if it could be a valve body issue. I’ve calibrated the dip stick so that the full mark is at the top of the pan. I’ve added a transmission cooler to try to keep temps down.
Hey Matt, the slip from 2nd to 3rd sounds like either a slip (cut seals on the center support or mis-installed lip seals on the direct piston or the center seal in the direct drum.
First thing I would do is contact the builder to see if you can bring it back for review/inspection and have it fixed under warranty.
As far as source, there can also be a problem with internal main line pressure, the modulator system, or even governor. I'd start w/line pressure...plug a 300PSI gauge and do a pressure test...Pressures should be between 50-65 PSI at Idle in P, N and D...Reverse, Manual 2 and Manual Low (1) should be twice to 2.5 times higher....If those checks pan out, go to the modulator: check to see if you have at least 12-14 inches of lift at the modulator with a vacuum gauge. If so, pull the hose off and check for trans fluid. If none found then you can remove the modulator and using a pen magnet, check the valve itself for freedom of movement. If all these checks pass, you can rule out the modulator...Then pull the governor out...check the condition of the gear as well as confirm that the valve inside the governor body moves when you actuate the weights by hand. If everything is ok so far, drop the pan.
Drop the valve body and make sure the 2-3 upshift valve moves freely in its bore. Then check the detent and detent regulator valve for the same thing (both those valves are in the same bore).
If all those checks pass, I would suspect a leak in the hydraulic apply circuit for 3rd gear (cut sealing rings or partially torn lip seal(s).
But as i stated earlier, I would first call your builder to see what he can do to help before doing any of the above yourself.
@@nickstransmissions back to the builder twice over past year. They test drove and checked pressures said “it’s all ok”. I’ve done everything you’ve suggested up to valve body inspection so will drop the pan and see if that could be the issue. Thanks for your input-much appreciated!
Forgot to say - no solenoid on this model.