I recently added a 2" lift to my '98 Cherokee XJ. All went well except for slight vibration during acceleration @ 28 to 32 mph, no vibration during decelleration. I'm picking up a gravity angle finder this evening to check the pinion angles. I'm sure the rear axle to driveline angle is out due to the installation of shackles. Can someone more experience guide me as to whether it would be better to do a t-case drop or add rear axle shims?

 

shim the pinion down
the angle of the drive shaft is irrelevant other than if it has to much angle
and you don't with a2" lift

so yo need to find the angle of the motor and trans
then set the pinion angle 1 to 2 deg less

so if the trans is at 7 the pinion should be at 5 or 6

 

 

So a static(parked) pinion angle of 1 to 2 degrees less than the engine/transmission angle will achieve proper geometry during acceleration? Am I understanding this correctly?

 

yes the springs will wrap a little and things will line up

 

Thanks for the advice. I believe 1 or 2 degree shims should do the trick, but I'll measure this evening to find out for sure. Do you have any ideas as to where I can get a kit containing axle u-bolts along with the shims? I would rather not reuse the u-bolts if at all possible.

 

a 4x4 shop wold be best
some auto parts will have them

 

Ok, I picked up a gravity angle finder this evening. I put the '98 XJ in neutral, rolled the it out several times to relax everything, and measured the angles. I measured it several different ways including the socket method. The transmission/engine angle is @ 6 degrees and the rear axle @ 11 degrees. This difference seems to be alot for a 2" lift, but I have read that 96 or later XJ's are more succeptable to vibrations due to a shorter output shaft plus I'm sure there is some settling of the springs @ 85,000 miles. Can anyone give any input as to whether this sounds right or not?

Mike 37, this means that a 6* shim would put me 1* below the trans angle which would be about right per your previous advice...correct?

 

yep 6 would be right
did you say that you used shackle to do the lift
if so by doing that you not only lifted the jeep but tilted the angle up by pushing the back of the spring down

 

So do you think that these measurements are in the ball park since I lifted with shackles? I guess I'm just trying to compare with threads I have read about 3 & 3-1/2" lifts that only required 4* shims. Then again, maybe they didn't use shackles?

 

if you checked your angle right then you need 6deg shims
don't worry about what other guys have

 

10-4, thanks for all your help and I'll report back after the shims are installed.

 

mike37, I appreciate your advice to this point. You seem to be very
knowledgeable and experienced on this subject. I've had feedback on other forums telling me 6* shims are too large and shouldn't be used. Before I order 6* shims, do you have any reservations as to these shims being too large as far as safety issues, etc?

 

I have the OME 2inch on mine and the TC drop and no vibes at all.

 

I think it's just that I've got a couple things working against me.

1. I've read several places that '96 and newer Cheroke XJ's are more succeptable to driveline vibrations and I have a '98.

2. The fact that I used shackles instead of blocks. The shackles definitely do kick the pinion angle upwards.

I want to believe in my measurements and go with 6* shims, but I'm concerned because I can't find anyone from 3 different jeep forums that have ran into this issue with a 2" lift.