rear caster angle

alright so heres the sitch. i put a 3.5 in pieced together lift on my 2000xj. the rear springs are RE 3.5's. i also thinking that i would need them because i read it on here i put 4* shims on as well (yes the right way) the only problem is now i have driveline vibrations.

I heard from a friend that I only add shims to address driveline vibs when they start happening.

My question is.... should i remove the shims? will this get rid of my vibs? or do i need different shims....or transfer case drop?

thanks!


oh and sorry i dont have a picture of it at the moment.

Are you running a SYE if not you should remove the shims. Unless you put them with the fat end of the shims facing the front of your rig. If you put them the other way around it will worsen your dive line with out a SYE.

no im not. after reading up on sye's i think i should remove them like you said. sounds like that should be the problem

Shims are for use with an SYE. At 3.5" I would be surprised if you can get rid of vibes without installing an SYE. '97+ tend to get vibes at anything over 3" without an SYE, although every XJ is different.

T-case drop may also solve your vibes but if you wheel your rig at all, you don't want a t-case drop.

Or you could grab an angle finder and not guess it, but you first need to decided if you will be running a SYE, T case drop, or neither...

If you are not running an SYE, the rear axle needs to be in the same same plane as the transmission. You need an angle finder to determine what shims are needed. You will need shims no matter what you do.
http://www.sears.com/craftsman-magn...p-00939840000P?prdNo=3&blockNo=3&blockType=G3
http://www.sears.com/craftsman-digital-torpedo-level/p-00948295000P
Driveshaft angle information.
http://4xshaft.com/
Geometry 101"
I have lifted several 97+ XJ and they all had rear drive shaft vibrations, even with shimming the rear so the axle plane is in the same as the transmission.
You will either need to lower the rear of the transfer case or add and SYE kit..
You can buy a transfer case lowering kit or make one.
http://jeep-xj.info/HowtoTCdrop.htm
You will need between 3/4-1" of drop.
Ideally, an SYE kit will be installed for best results, especially if you go any higher.

No one can tell you what size angled axle shims you will need until the angles are measured.

Could have swore I just answered a thread just like this one a few days ago - LOL!

Axles don't have "Caster".

This is basic driveline 101

Since you are running a OEM driveline:
1st: Remove the shims, you went the wrong way with this mod.

* Driveline angles need to equal and OPPOSITE, not the same (within a degree or so). Picture a stretched "Z"

*Output of the T-Case angle should be down.
*Input of the Axle angle should be up.
Measure with and angle finder and a 14mm socket at the yoke caps. Compare the angle on the 2 yokes (The fixed yoke and the one on the DS), and the difference is your angle. Do this at operating height.
If you want, you can shim under the cross member.

Rustys makes a 1" drop cross member which does not change your ground clearance.

If you run a shaft with a CV or double cardan joint at the T-Case (Like the front shaft), the driveshaft angle must be zero degrees or just a tad lower the pinion (Again, look at the front shaft). This is because the CV or double cardan is doing all the work splitting the driveline angles and the rear joint is just a coupler.