shimmed and still vibes...

Hello buddies ! I just had my xj lifted last week. Itss a 99 cherokee sport and i kindda did the budget boost from rock lizard. The front is all right but in the rear I had my leaves rearched and added a leaf in each pack. It got me at 2 3/4" in front and 3 1/2 or little more in the back. I left with no shims and no t case drop to see if it vibes. And it did while accelarating and deccelarating. I went back to the spring shop ad they installed me 6* shims since He only had those or 2* not even 4*. So I left again and it was still vibrating, not even less. So Im wondering... should I try a tcase drop or check my u-joits, maybe both !?! Are 6* shims too much with a t-case drop? Any t case drop kit under 1" ??? Many many questions, yes ive searched but couldnt really find the exact info.

Thanks a lot for your help guys! Tony

* 6 seems a bit much for 3 1/2 inch lift. measure agle and install what you need, not just he has. you can order the right ones. do you have an sye and cv shaft intsalled?

look at this:

http://www.4xshaft.com/

go to "tech info" at the top
and then click "geometry 101"

Well without angle measurements it hard to say whats going on.Other than that,do a search on 96+ needing a SYE kit.

I had to try several different configurations with my lift. I installed an S-10 bastard leaf pack and 4.5 RE coils up front. I ended up with 3* shims (with the pointed end facing the front) and a 1" TC drop with a brand new transmission mount. After several different configurations I found that this one worked for me. No vibes.

Its a pain to keep dropping that rear axle to get it right, but it will pay off. Just some advice, buy new centering bolts each time you take the packs apart. You might also consider having extra U-bolts handy.

Good Luck,

James

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use one of these and it shouldn't take several tries to get it right.

http://roofgenius.com/roofangle.htm

angle finder

available at most hardware stores

Got the same angle finder at harbor frieght for $5.95. On my 92 (AW4, 231, D44, 3-1/2 lift) and bastard pack (durango & XJ) I needed a 1" drop (7/8 would have been better) and 3 deg shim to get it all lined up (+/- 1/2deg).

You must measure the angles to do this right. Factors that affect are: rear lift, arch position, , pinion yoke distance from axle (D35, D44 & 8.25 are all different), tranny type, tranny drop, weight over rear axle, lift on front end...

You can guess at this until it feels good but you can be misaligned, not feel the vibes and still wear out u-joints in a big hurry or you could get lucky and never have a problem. Seems that there is no rhyme or reason to what you can get away with and what you cant, to many variables in play. Phased the shaft correctly and joints will live.

John

PETEY said:

* 6 seems a bit much for 3 1/2 inch lift. measure agle and install what you need, not just he has. you can order the right ones. do you have an sye and cv shaft intsalled?

look at this:

http://www.4xshaft.com/

go to "tech info" at the top
and then click "geometry 101"

Click to expand...

I only have shims, no sye and no t-case drop...

Stonycar said:

I only have shims, no sye and no t-case drop...

Click to expand...

... and vibes.

The point of that link was to show you that you need your x-fer case output to be parallel with your pinion gear to eliminate driveshaft vibes. IF your geometry is good to go, most likely you are exceeding the max operating angle of the u-joint... and again are getting vibes. With the set-up you have now, there is no ammount of shimming in this world that will eliminate your vibrations.

If you want to get rid of the vibes on the cheap, throw in a tranny drop and shim your rear axle so your x-fer case is parallel to your pinion. <--- not recommended.

If you want to get rid of the vibes the right way, get an SYE and shim the rear axle so the pinion points SLIGHTLY below (while the Jeep is on the ground) the x-fer case output shaft.