cf1k1

Why? This where you gather all the information. Is it an automatic or a manual? To see of its truely the u joints, get up to speed where it vibrates an note the rpm. The the truck in a lower gear and get to those rpms but not the same speed. If the vibration persists, then it's an engine issue.

black2000xj

its a automatic jeep, aw4 trans, 231 t case

no vibrations up to 45 mph...anything after that it vibrates...you let off the gas and it goes away, and as soon as you touch the gas it vibrates again

but no vibrations up to 45 mph...after that it does

AND A BIG THANK YOU FOR YOUR TIME>>>!!!!

cf1k1

No problem. It sounds like the u joints.

JAYSSICKXJ

Dont forget.. it could be a tire out of balance.. mine would shake at 50-54 then stop..found out i had weights fall off..

crux

Sounds like a real PITA so if your looking to buy it then consider it in the price.

In all Honesty I would start with balancing tires which most likely would not resolve it, but it is a good starting point.
Next have the drive line looked at. Speed up over the 45MPH mark to 55 MPH and see if it goes away. Punch it at 50 did it get worse? Let off did it go away? If so then it is a drive line issue.
Did the guy install new motor mounts or a tranny mount when doing the lift? Another possible source.

Front end is a rather weak link on the XJ to start with. I would hit the jy pulling all parts off a ZJ as they are heavier duty and have it aligned afterwords.

black2000xj

yea he didnt do anything other than install the lift kit and new rear leaf springs. He said it was perfect before the lift...right after the lift went on is when the vibrations started. Its a driveline vibration too....its not a shake from the wheels or tires...its definetly in the drive line....My concern looking at this jeep is: What if its not the u joints in the drive shaft...then what

I can do u joints pretty cheap, and if thats what it is, i have no problems with it, but i dont know 100% that u joints are the issue...he is going to take it back to his mechanic and have him check or replace the u joints ...so im waiting

in the mean time i found a couple others....1993 cherokee with 122k miles! and a 1999 with 114k....i like the old style jeep, but the 99 dont have the cylinder head issue and it has cup holders ...so i got alot to think about!!

944.0

It sounds like u joints to me as well.

JeepDeep

U joints or pinion angle or a combination. Not expensive to fix either so use it to your benefit and low bal the guy for a great deal. The angle at which the yoke exist the transfer case has to equal the angle the yoke enters the differential.

black2000xj

Ok, if its the u joints, will they keep going bad due to the lift, or do you think these are the original u joints, and they are just bad due to age

what made them vibrate after the lift? is this going to be a on going issue?

JeepDeep

The leaf springs may have changed the pinion angle if they were installed with different shackles. Do you know what leaf packs he used?

If the pinion angle IS off and it is corrected chances are your vibes will be solved.

black2000xj

I dont know...he doesnt seem to be returning any of my emails

is it still a easy fix(ish)??

TheJerm

Sounds like you narrowed it down to rear DS, so yea its an easy fix. This is a common issue with XJ's, even worst with wranglers. I had to do a tcase drop to remove the vibes after a 3.5" lift on a '00. Not the best solution but only costed $10-15 for it.

1st check the pinion angle, pic would help
2nd Change Ujoints if angle is OK
3rd tcase drop if 1 and 2 dont help
4th save money for SYE

SYE are the best solution for many reasons. My favorite: if you break the rear DS you can pull it, drive in FWD and not loss any tcase fluid.

JeepDeep

Shims can be used to correct it. If there are longer shackles they can be replaced with stock ones to correct it. It's not too difficult but you should make sure the pinion angle is off to ensure you have identified the problem.

If you know where the Jeep is take some pictures of the leafs and shackles and then take some pictures of the driveshaft with t case and diff ends showing and post them up. If the vibes are bad it should be visible without measuring the angle.

kentuckyscott

I have a 3 inch lift on mine and it did the same thing. An alignment helped a great deal and either a TC drop or SYE will do the trick. 3 inch lift doesn't sound like much but it does change the angles under there quite a bit.

black2000xj

so it sounds like i should replace the u joints first, if that dont help to get a t case drop

whats involved in a t case drop