In need of some help, I still have vibes and its driving me crazy

Ok so short history....94xj, aw4, 242, 8.25, HP d30....3.5 superflex w full packs. RE H&T sye with front driveshaft in rear.
Did the lift, vibes, did the h&t, vibes. Shimmed the rear axle with 4* shims. still vibes. replaced u joints, still vibes!!!! I'm just getting really discouraged here and its cold as hell to be out there still fooling with this thing!!!
If I pull the front shaft I dont have as bad of vibes, but it also feels like pulsing kind of vibrations in my rear shaft when the front is out. Theres about 1" or so of the slip joint showing in the rear (is that too much??) My angles for the rear are about 3* difference between pinion/shaft angle.
As for the front I'm sure my camber isnt as good as it can be, and my front angle is not exactly 0* but its close, maybe 2* low. The problem there is, my control arms are as far back as they can go, which means the front pinion is what it is unless I get adjustable UCA's to bring the pinion up a little more...But I see so many people with RE SF and dont have that kind of problem! I'm trying to cover it all here, so if anyone can help or offer any kind of advice, I'm all ears and appreciate anything to come!!!!!!!!!!!

here are some pics to see what I'm talking about...1st rear shaft with slip showing, it looks like its extended a little far and maybe I'm not getting good engagement?

and the front, from looking at it, the angle is really really close to 0*, and you can also see the control arm bolts to the far rear of the alignment holes

I'd look for a ZJ front driveshaft (about 1" longer) and take it to a shop to see if it's balanced.

I actually have one, it seems almost too long! It seems like its either one extreme or the other, if I only have a 1/2" of slip slowing would that be ok? or is there a great amount of flex in the shaft that I'm gonna bottom it out?

Don't know what a ZJ shaft would do, and usually the front shaft doesn't need to be modified at all.........if anything, a touch shorter, not longer.



You're problem most likely has to do with angles. If the u-joints are good, and the angles are correct, you won't have any vibration. Both the front and rear pinion/driveline angles need to be 0*. The rear is usually best at 1* down since it will spin up just slightly under acceleration. If the rear angle is still 3*, that could be the problem. If the front still vibrates, you need those adjustable UCA's. There's no magic, get the angles right and it won't vibrate.

Uh...the rear at 0*??? not if he has an SYE...you want the pinion pointed at the TC...maybe a degree or two down...but you dont want your rear pinion at 0*....you want it tipped up...

well I just sent my bro to quadratec to get me some 6* shims. So I'll throw them in tonight and hopefully that at least solves the rear issue. I can live without a front shaft for now!

Does everyone with RE superflex need to get adjustable uppers or is my jeep just a picky bastard!!!!!!!!!!!

JNickel101 said:

Uh...the rear at 0*??? not if he has an SYE...you want the pinion pointed at the TC...maybe a degree or two down...but you dont want your rear pinion at 0*....you want it tipped up...

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I'm gonna take a wild guess and say he meant at 0* meaning inline with the driveshaft, not 0* to the ground. Since right now its about 3* below what the driveshaft angle is.

Backroads said:

I'm gonna take a wild guess and say he meant at 0* meaning inline with the driveshaft, not 0* to the ground. Since right now its about 3* below what the driveshaft angle is.

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Yeah, re-reading it, I see what he meant now.....

I need more coffee....:speepin:

Im gonna guess that the new shims solve your problem. I had the same issue with my RE 4.5" lift and the 6* shime solved my viberation problems completely.

let us know!

now the next problem....for being all mighty quadratec, they really dissapoint me. I called, asked for the shims, 'yea we have them in stock' asked him if they were steel shims, YES they are....drive down and wouldnt ya know, theyre aluminum. I don't know if I trust using aluminum shims. So of course the only other option is wait yet another week and a half for rubicon shims or something similar.

they are made by superlift. 2" wide. made of tensalloy aluminum (according to superlift.com) What are everyones opinion on that? The aluminum just makes me nervous

Backroads said:

now the next problem....for being all mighty quadratec, they really dissapoint me. I called, asked for the shims, 'yea we have them in stock' asked him if they were steel shims, YES they are....drive down and wouldnt ya know, theyre aluminum. I don't know if I trust using aluminum shims. So of course the only other option is wait yet another week and a half for rubicon shims or something similar.

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I've had a similar experience with qtec, in my case it was axle U-bolt lengths. I try to avoid qtec even though I can run over there during my lunch hour. Unfortunately I don't know of any place else local that would have shims. You might want to try Jason at jeepinoutfitters. I've have good luck and good service with him.

I have a set of steel shims (can't remenber if they are 4 or 6 deg though) you can borrow if you're really in a rush or just want to test if they will solve your problem.

Yea I'm starting to feel the same way about that. Just to rant a minute, why the hell would they not have U bolts, Center pins, Shims, etc etc if they specialize in jeep stuff, and lifts and all!!! I'd be willing to bet that every one of those cherokees in their catalogs has all those items on them to make them look so good....

Anyways, I have 4* ones in now, I need 6*. I dont wanna borrow cos its enough of a PITA to put them in, its too cold to be fussing with this stuff anymore I was hoping to just be able to drive the damn thing by now lol!!!

It does suck that they don't carry the little items you actually need. They did have u-bolts, rancho if I remeber correctly, but they were too short for my needs. So I had to order and wait. There are some spring places around here you can get u-bolts from, but they were only open when I was at work.

I actually had a buddy of mine (machinist) make my shims because I was inpatient too.

Not too cold in a garage.

oh I have a garage, and heaters, but still! you know how long ive been fooling with this crap now!!!!!! i was hoping to be all good by the time it snowed (which is a day too late at this point!!!!)