yellow97XJ

First ill give some info on the jeep:
6"lift w/ control arm drop, 4.0 5-speed 97xj D30, 8.25rear, 231 t-case, 4.10gears

was destroying u-joints every other day, i figured the pinion angle was off cuz one of the shims between the leafs and axel was mostly gone, i replaced them with 2 degree shims,(think the old ones could have been 4 degree, dont know if that will make much of a difference) tighened everything up and the vibration was still there but significantly less, the u joints are wearing slower now but are still wearing quick. maybe the pinion angle is off? maybe the driveshaft is unballanced? i have no idea.

any ideas or suggestions welcome

please help

ol"blue

Pics would make it a lot easier to help diagnose your problem.

4.3L XJ

There could be a number of issues here. One thing is that many people just add axle shims because they have a lift. But you have a 6" lift. At that height, the u joints yokes will start hitting each other and this will knock out your joints quickly. Do you have a slip yoke eliminator? With a 6" lift it is almost mandatory, along with enough axle rotation to tip the pinion up so that it is aimed directly at the back of the t case. It sounds like you have enough vibrations to loosen things up. Check all your bolts.

MasterShakeXJ

sye? adj tracbar? balanced tires? alignment?

yellow97XJ

have a sye, the vibration is deffinately in the rear because it goes away when i take the rear driveshaft off and drive around in 4wd. has an adjustable track bar, alignment bad,(Bent adjusting sleeve), but i dont see how that would cause a driveline vibration.

im not sure how pics would help, maybe to see the pinion angle? let me know what kind of pics your looking for ill try and get them.

on other thing that i dont know if it would contribute to this, but i put a new pinion yolk in and im pretty sure it was one from a D35 not a 8.25, it fit fine, however it was about 1/2 inch longer. maybe put the old one back on, but one of the tabs that hold the u-joint in is broke off so it might still vibrate.

4.3L XJ

So you have a double cardan u joint at the forward position? What is teh angle of your pinion?

yellow97XJ

not sure what kind of u-joint that is, its just a stock jeep u-joint.
not sure how to measure the pinion angle, never really had much experiance with differentials and pinion angles ect...

4.3L XJ

If I had your Jeep in my driveway I could figure out what is wrong in a minute. But I can tell you are new enough to this that it is difficult for us to communicate. Send me some pics and we will get this figured out.

yellow97XJ

what do you want pics of? pinion angle? let me know what ya need and ill work on getting them on this old *** computer

muddeprived

Before you do anything, check your pinion angle:

http://www.stu-offroad.com/axle/pinion/pinion-1.htm


The angle of the pinion should be 2-3 degrees less than the driveshaft. So if your driveshaft is 14 degrees, your pinion should be 11-12 degrees. When you accelerate, the leaf springs produces a slight wrap and the pinion rotates up a little and it would be even with the driveshaft like it should be.

dangerousdavid

mine was a three inch lift that actually lifted it something around 5.5 and i had to use 6 degree shims.....thats probably what it is...you might have to clearance your yokes also.

yellow97XJ

read that article, how do you correct it when you have leaf springs?

dangerousdavid

just put higher degree shims between your leafs and perches

4.3L XJ

That may be his problem. I don't think he has a CV joint to do that. Send us some pics to get it right.

muddeprived

degree wedges or shims that go between the axle mount and leaf spring. They are bolted on with the leaf spring's center pin.

http://www.rubiconexpress.com/Builde...px?folder=BPDS


See the pretty silver thing under the leaf spring? That's a shim and it rotates the axle.