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Cannot Solve XJ Driveline Vibrations

hackattack182

NAXJA Forum User
Location
VA
I recently bought my first XJ, and the rear leafs were shot. So I opted to just lift it instead of putting OEM leafs in it. I used the Rubicon Express 3.5" Super-Ride lift kit, installed with a mechanic buddy at the shop that he works at.

I did a ton of research on it ahead of time and ordered a t-case drop just in case I had driveline vibes... I did. I put in the t-case drop, which didn't really help it. I then used an angle finder to check to see what my output and pinion angles were looking like, and from my measurements (as best as I could) it was about 2.5 degrees off on the pinon, so I put some axle shims in there to see if that would help, but it really didn't do anything. I also replaced the U-joints, still did nothing.

My buddy has a friend that has done multiple lift kits on Jeeps and other vehicles. He visited the shop the other day, so my buddy let him take it for a spin to help diagnose. He seemed to be confident that it was a bad ring and pinion. All of the research that I have done has not brought me across this issue before, so I wanted to see if anyone has come across it.

I essentially am weary to throw new gears in it (as I know it is expensive as well as difficult). I also know that SYE's commonly fix driveline vibrations, but if making the angles closer didn't help it, wouldn't that indicate that putting an SYE in wouldn't really remedy the problem?

I just don't know where I want to dump the money essentially. I was hoping someone has had a similar situation to mine and been able to fix it... At this point, I am regretting even putting the lift in to begin with, so frustrating not being able to use it.

Thanks
 
Have you pulled the front shaft and test drove again? Does it vibrate constantly or change with load? If there was no vibe before the lift I highly doubt your ring and pinion magically went bad.
 
Have not tried pulling the front shaft yet, definitely feels like it’s coming from the rear. It definitely seems to be load dependent. If I push it hard between like 10-25 mph or so, it gets violent....I also agree about the gears. Not sure how lifting it would impact that at all, unless putting on 31s just made it more stressed.
 
Throwing parts at an undiagnosed problem in the hope of accidentally fixing whatever is causing the symptoms is not a good idea. If the vibrations coincide with when the lift was installed, the ring and pinion are likely not the cause of the vibes.

At about 3 inches of lift, late model XJ's need an SYE. The T-Case drop you installed may not have eased the driveline angles enough. Besides that, a T-Case drop should be considered a temporary patch until an SYE can be purchased and installed.

As suggested, remove one drive shaft and go for a test drive. Re-install that one and remove the other and test drive again. Now you should be able to pinpoint the source of the vibes.
 
When I installed my 3.5" lift I had Vibes. Dropped the TC 3/4" it helped but didn't eliminate. Dropped TC down to 1" and vibes nearly disappeared. Then my rad fan reached up and ripped out my over flow hose that was hanging a little too low Made quite the noise.

Like Tim said, consider it temporary.

I have since installed a Hack-N-Tap and 6* shims with a used front XJ drive shaft. Needs to be replaced with a better shaft. Doing a lift is fun but seems to always require something else. lol
 
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Check out Tom Wood's site for the proper way to set the driveshaft angles, depending on what type of driveshaft is used.
http://www.4xshaft.com
Lowering the transfercase does reduce the rear driveshaft's angle but it increase the front shaft angles.
A common source of vibs is the front driveshaft's u-join pinion angle, at the axle.
It's angle should be less than 1 degree. Lifting will increase the angle, a dropped transfercase will make it even worse.
Adjusting the pinion angle will also change the caster.

Like the others, I have never heard of a bad R&P causing vibs.
 
With a stock rear drive shaft and a lift it basically is making the shaft too short. Not enough spline engagement. Dropping the TC slightly is allowing more contact. Think of barely putting the end of a drill bit in a chuck and turning on the drill. The drill bit will not spin true to the drill if under a load.


Sent from my iPhone using Tapatalk
 
Thanks for all the comments and help everyone, really appreciate it....So I went to prep everything to install my RE Hack and tap, and it looks like there is some runout on my t-case output shaft. So yeah that sucks. Looks like I’ll be putting in a full SYE after all, because im not going to throw a slip yoke shaft in there obviously....Out of curiousity, has anyone experienced a bent output shaft before?
 
I have a little experience in this area of mystery and confusion. Lifted a 97 xj 4.5, rear leaves were a shim style pack from the factory. I lowered the t-case an inch and never had an issue. Had a 90 lifted 5 inches, no vibes. 93 4.5 no shims no tcase drop, no vibes. and now a 99, 6.5" longarm with a SYE, slight vibes. Every XJ is different, I would suggest putting in a SYE and then shimming lightly. Im going to try 2* shims on this jeep to correct the angle. Do yourself a favor and save money by using a stock XJ front shaft, and check your u-joints for wear! that alone can cause vibrations where a new u-joint would fix your problem. Good luck bud
 
Thanks for the response Sentry. At this point, I installed the RE hack n tap SYE, and when I was doing so, I noticed the output shaft on the tcase seemed to be bent. I installed it anyway to get it slightly drivable.. I picked up a front ds from the yard, put new u joints in it, and shimmed the axle correctly, and still have the vibes. So at this point, im pretty much certain it is from that runout on the output shaft, so I am going to order an actual SYE here shortly and throw that in. Let's hope that will be the end of it.

Thanks again to everyone who has given me some input here, I really appreciate it. I will update after I put the full SYE in.
 
My 96 did the same before i did an sye. Pull the slip yoke out and cover with anti seeze. It helped mine for a little before it started chewing the splines up and then it sounded like a chain saw on throttle lifts. I didnt run a tcase drop.
 
Hey guys-

Just wanted to update here. As I mentioned, my stock output shaft was definitely bent, and even cutting it down to do a Hack n tap didn’t help with the runout. I finally bought an actual SYE from rugged ridge, spent the day yesterday putting it in, and the vibe is gone. Not sure if I bent it during the lift kit install somehow, or if it was always bent and it just didn’t matter when the suspension was sagging so much. Either way, it was bent and replacing it with an SYE did the trick. Feels great now!

Thanks again everyone for the input, really appreciate all the pointers.
 
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