3.5 inch lift.

[FallibleXJ]

As many before have stated, I have the same.

3.5" RE (closer to 4-4.5) on 31's. Had small vibes but I through in a 1" T-case drop, all went away.

 

[DoctorPhate]

I believe I am getting mixed suggestions here. but atleast I know that with a 1 inch t-case drop I can get rid of any vibes that may come from a lift kit

 

[FallibleXJ]

Exactly, I didn't put in the drop until about 4 months later. I had to drive cross country and decided I'd rather not have any vibes for it. But for general use it was just fine, only really vibrated when traveling 45-52mph.

 

[lazyxj]

[FONT=&quot]When it come to needing an SYE it seems every XJ is a little different, with the 97+ XJs more prone to it.
Everyone's sensitivity to feeling vibes is different. 30+ years of professional wrenching has made me very sensitive to all sorts of noises and vibrations. A modified XJ is the perfect thing to drive me crazy.
I felt rear drive shaft vibes in my 2001 when it only had a 2" lift.
An XC drop reduces the rear axle vibes but increases the angle of the front drive shaft. If you are going to lift it higher, consider biting the bullet and doing the SYE now. Jeep should have included it from the factory.[/FONT]

 

[89xj]

I believe I am getting mixed suggestions here. but atleast I know that with a 1 inch t-case drop I can get rid of any vibes that may come from a lift kit

thats because there is many different ways to lift it.

if you have the money, get 3" coils, 3" leaf packs, adjustable trackbar, shocks, extend your endlinks or get quick disconnects, extend/bend brake lines.

wheel that for a while, then if you need more height you add a budget boost, spacers and shackles, and lower control arms.

or buy a 4.5" kit and be done with it.

 

[93gc40]

So i should try to get 6 inch long shackles then? 6 inch shackles = 3 inches lift right.

No, that will get about 1" of lift, as the stock shackle are about 4" long, +2"=1"lift.

As to your original question and affects of lift on vibration. The answer are going to be all over the place because no 2 XJ's seem to react the same to a given lift, and prefence and use varies with each driver. It is possible to run 35" tires on stock suspension, with enough sheet metal trimming and bump stopping.
I would say to avoid blocks, use shackles instead up to 2" of lift. Over 2" use shackle in combination with full springs, or AAL if on a budget. Just know that the AAL will not be as long lived or flexy as full spring packs. Do TC drop first if you get vibes, but plan for SYE especially if going over 4".