Vibe woes

siminsez01 said:

I have a 97 cherokee dd. front 1.75 spacer rear shorty add a leaf. got 30" mts that DO NOT RUB , and a 1" tcase drop that took care of the slight vibes the bb gave me....The rear is saggin a bit, so i got some 1" daystar shackles... installed them and horrible vibes so i've tried the following:
3 degree shims with the big part of the wedge facing forward (to correct the change in angle caused by the shackels)
dropping the tcase an extra .5"
and both concurrently
i got the worst vibes from the combination of both..... should i have faced the shims in the other direction?....i didn't think so based on the angles i was looking at and trying to keep the tcase and diff in the same planes.
what do i do....i want to be albe to get rid of the t-case drop altogether eventually bc it kills my ground clearance.
should i think about an sye, i've heard of them but what does this mean? will it solve my problems of the vibes and allow me to get rid of the tcase drop?
any help greatly appreciated. i know that vibes are trial and error, but knowing your trials and errors will help me not make so many

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Buck Jackson said:

97-2000 cherokees that are lifted often get vibes that result from the front driveshaft not the rear. The way to check for this is to remove your rear driveshaft from the vehicle, shift into 4high and drive around a bit. If you still have vibes, they are due to the front driveshaft. If there are no vibes, undo the front driveshaft and drive around in 2high on the rear shaft only. If the vibes are there, its the rear shaft. After that consider these:
The t-case drop will often solve the problem on a low lift like you have. I suggest getting rid of the longer shackles and adding in another cheap do-it-yourself add a leaf. You can use any 2.5" leaf and mix and match the packs to produce the lift you want. Adding another stock cherokee top leaf to the pack often produces about 1.5" of lift. This would probably give you just what you want in terms of lift.
You did put the angled shim in correctly, but my question is, did you check your angles to ensure that 3* is what you needed? What do they measure now? Your tcase angle needs to match your pinion angle exactly for the shaft to phase correctly. If the angles do not match exactly, that is probably where your vibes are coming from. Make sure you use an angled shim that will return the plane to the same it was before. This is why i recommend getting rid of the longer shackles and just doing another add-a-leaf.
In the long run, definitely get an SYE and DC shaft. This is the best mod to resolve your angle and vibe problems, but it is definitely spendier than dropping the tcase. When i first lifted mine, i just drove around with the vibes until they ****ed me off sufficiently to warrant spending the money on an SYE. I cheaped out and went the hack n' tap route, but i recommend the HD SYE if you can afford it.
Good luck with everything,
Buck :canada:

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MaXJohnson said:

Buck Jackson ALERT! (AKA SPOBI ALERT)

The common problem with 97+ XJ's is the design of the transfercase output, not the front driveshaft. Also, you don't need the angles to be exact. The pinion angle is typically set a degree or two lower than the transfercase to allow for spring wrap. Get within a degree or two of that and you should be good as far as angles go. If you do a modest lift AND get your angles right, you might get by without vibes or you may find that a SYE is still necessary. But, it doesn't make sense to have a discussion on drive line angles when you don't specify what the angles are. You're not giving the others the information they need to help.

In other words, This thread sucks without angles.

None the less, your first problem was to use the "short" add-a-leaf. These are universally known to be a problem.

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kmagnuss_2000 said:

#1...you put the shims in backwards.

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