JL and JT FAD. Delete it or not? That is the question.
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- Опубліковано 9 вер 2024
- This is a video that I filmed at last minute. There is nothing really being done except discussing the FAD on the JL/JT platform and whether or not deleting it is the way to go. I have mine deleted but are now running into a situation where due to factors with my build I may not be able to stay that way. Again, this video doesn't really show anything other than the subject being discussed. Hope this helps anyone else considering this route.
I have a Rubicon JT with 3.5” Teraflex , 4.10 w 35s, I was planning to re-gear to 5.13 w/ 37s & the fad delete but after watching this I Think I’ll just buy another set of 35s & stay where I’m at. Thanks for the heads up & honest review.
I wouldn't not regear and go to 37s. That was how my JT was set up and honestly it rode and drove great. 5.13s and 37s worked very well and it could pull 8th gear on the highway all day long. Just keep the FAD. Whether you keep the factory driveshaft or go aftermarket but will be fine and you won't have any vibrations if you keep the FAD.
Great video! I learned a lot, I have a 392 and the FAD is deleted, but its really just a cast cover with the fork cast into it to keep the shafts permanently connected. Sadly it's not one piece like it should be, FCA is too cheap to go that far. They try to reuse as much of the standard rubicon parts as they can. Nice, shop... I subscribed.
Man I drove my 18’ JL with the ultimate 44, no fad, for nearly 5 years. Never had an issue. With 5.’13’s. I think the key is not to lift too high though. Mine was about 2.5”. Mopar lift but base model sport.
However, I think the FAD in the JL/ JT is fairly reliable. Besides the housing snapping in half haha.
Another note, I also only had lower adjustable control arms.
I mention in the video that the Repezza joint actually handles steeper angles. It is actually a good joint. The biggest downfall is the diameter of the driveshaft and it limiting the droop of the suspension.
The FAD is for mileage. Your problem is not the FAD it’s your geometry. Pinion angle vs caster is different with the double cardan driveshaft. it’s the exact same as the JK. I had the same issue with my built JK when swapping to a double cardan driveshaft and 5.38 gears. The FAD itself is also a problem when the bushing between the piece shaft starts to wear.
My XR has 4.56 gears with stock driveshafts 3.5” lift on 37s no issue. In winter I run it in 4auto 90% of the time the other 10% its in 4Hi.
The biggest downside of the FAD for me is, I had a wheel speed sensor fail in a winter storm. When that happens you have no 4wd, the FAD will not lock up.
Personally I’ll go with a high angle Rezzepa joint rebuild kit for my driveshaft before I go double cardan again.
I had wheel speed sensor issues so I now carry the 392 FAD block plate so I can disconnect the electronic FAD and mechanically lock the axles.
All the new Rubicon X with all engines are all FAD delete. That means they are running up to factory 4.88 gears. All Jeeps with full time transfer case in 4Auto also run with the FAD locked with no issue.
I originally thought that it was mileage as well. It was the techs at Adams that told me it was due to the increased angle of the front driveshaft. They told me any JL/JT with 3" or more in front, the FAD deleted, and an aftermarket double cardan driveshaft will experience vibration. You are correct I could lose some caster to try and help the driveline angle but that would drastically affect the handling of my JT with 4" of lift in the front. So, in my case, since I had just purchased a brand-new Adams driveshaft, I opted to go back to the FAD. Knowing what I know now. I may have just rebuilt my factory driveshaft. From what I understand, Teraflex offers a replacement Repezza joint for the driveshaft. It is for a JK but you can then replace the JL/JT yoke on the transfer case with one for a JK and you are good to go. Of course, that would work but then my suspension droop is still limited by my front driveshaft contacting the crossmember. The aftermarket driveshaft does not. Ultimately the video was to try and put information out there. There is no wrong answer, only different scenarios and people need to understand how one decision can possibly create another issue.
The only reason I mentioned gear ratio in the video was the potential more or less vibration because of the driveshaft rotational speed. Again, every build is different and there are many factors to take into consideration.
@@jefftenhave8038
@@millstonejeepworx yes it really is the same scenario as the JK. Too much lift can case driveline issues that’s why aftermarket axles like Dynatrac have the option of an extra 4 degrees on the Cs so you can get better caster.
@@millstonejeepworx correct the steeper the gears the more prone to vibration. Here is a good explanation why the difference between the double cardon driveshaft and Rezeppa that the driveshaft guys dont like to mention. I ran the J E Reel driveshafts on my JK with 5.38 Yukons. I also found that running Geometry Correction Brackets helped balance the caster by correcting the CA geometry.
ua-cam.com/video/YgNZfIR-8Ng/v-deo.htmlsi=UBzoUlyz8v5ENH1w
If you want to get this fixed the answer is to swap out the front axle housing with one that has an increased offset between pinion angle and caster. That is, a raised pinion angle that points the pinion towards the transfer case output shaft. Dana, Dynatrac, Teraflex all have housings that will do the job.
Thanks makes perfect sense. You explained it perfectly. Thank you. It was something I didn't even consider
Maybe an idea, but could be costly. I saw a wile back that Teraflex has/had a kit to make a full floater of the Dana 44 front and/or rear.
I have a 23' JT Rubicon, 3.5" lift, 4.88, 37's, Adams front driveshaft, RCV's with the FAD delete. I get a slight vibration at 40-45, then a stronger vibration at 70-75. Any speed in between has no vibration.
Changing factory geometry is even more work than I thought. I'm scared to deal with all the driving dynamic issues after big lifts, now there is this driveline angle. It surprises me they tilt the transfer case, though It make sense to drive the rear wheels better. If we are trying to have a lot of caster with big lift, why isn't the diff housing pointing up during assembly.
I was one of the first people that had this problem on a 392 I put the Rockcrawler 4 1/2 inch lift kit I went through five driveshafts in one month and eventually cracked my transfer case it was an absolute nightmare we could not get it to work I had to lower the vehicle down to a 3 1/2 inch lift then it worked out but I had the investment in longer shocks 40 inch tires etc. etc. it was so bad I had to lower the vehicle more repair everything and then sell it with a big loss it was an absolute nightmare I went through OE M Dr. shafts and custom drive shafts and the driveshaft manufacturers for custom we’re trying so hard to help me but nothing would work
Sorry to hear you went through this. I've had many suggestions from people. Reduce your caster, go to aftermarket axles, etc. The fact is while not bad suggestions they aren't always viable. Reducing caster will cause handling issues. Aftermarket axles are way out sight price wise for most people. It is just sad that the design of the JL/JT platform increased that angle between the axle and transfer case as much as it did.
There is a company making portals for jeeps and that is a great solution but like aftermarket axles is very expensive. The best answer I was told by techs at Adams Driveshaft was 1. Keep the FAD if you have it. 2. If you choose to delete it or don't have it, as with the 392, stay 3" of lift or less.
wouldn't an atlas transfer case resolve a lot of the issues?
you could get the Yukon free spin locking hub spindle kit but you would have to go back to using U-Joints axles to use the longer outer axle shaft for the longer spindle. I don't know if RCV makes a longer outer shaft or not.
I was wanting to change my JLUR to the single shaft on passenger side but leave the FAD connected so I wouldn't get any computer errors.
I haven't heard any other videos having the problem you have after the delete.
typical ram 2500 problem with only a 3 ich lift...you need a way to clock the transfer case down...the hum come front the driveshaft
Commenting here because I have the same problem at the same speed with the same setup. 2 piece axle on the way and FAD going back in.
When you lift the jeep from the suspension and not a body lift, the axle pumpkin stays the same but the transfer case rises. Drop the transfer case 2”. It will still be high enough to clear more things than 80% of the components including the rockers.
I know of and have done transfer case drops in CJ, YJ, and TJs. Never heard of it or know of any manufacturer doing it in JKs or JL/JTs.
@@millstonejeepworx you have nothing to loose if you drop the crossmember 1” and see how that works. I’d bet it wouldn’t change much on the 4x4 lever. Then go from there.
@@millstonejeepworxcompanies are making better money selling driveshafts and yokes than drop kits. Just run a test.
@@alejandrovictoria5424The transfer case is bolted to the transmission, the transmission is bolted to the engine. You can't lower the t-case without lowering all 3. It's not a thing for JL/JT or even the JK.
Think before jumping..!! Hmm
Sounds like one thing leads to another
Very much so
I wish jeep still had locking hubs on the front axle
This sounds like a very complicated matter with all this stuff, your talking about. Engineering complicated headache. Just my observation.....kinda scary to me.
Just the transfer case end.
Sound like you need to rotate the C’s
take the spacer out