I bought a 99 XJ with 95000 miles and a 3 inch lift about a week ago, and i just noticed that every time i accelerate at over 30mph i get a vibration sound. but once i let my foot of the gas it goes away. it doesnt happen at speeds below 30 and gets really bad around 60 on the highway(at 60 it vibrates no matter if i am accelerating or not).. what can be the problem?

 

may be in need of a slip yoke eliminator...rear driveshaft angle could be giving you the vibes...

 

sounds like wheel balancing could just be a leads come off one of your front wheels check as this is very cheap fix.

 

would that really be the problem with a 3 inch lift. from what i read online a SYE is not usually needed till 6 inches of lift is put on. but i may be wrong, this is my first jeep.

 

have read your question again and vibs at 30 and 60 is balancing

 

oh the newer model xj's...you need an sye above 3 inches or so...but it varies jeep to jeep. i put on a 2" spacer lift on my 01 limited...and i got vibes from it.

edit: older xj's have a different style output on the transfercase, so they can get away with more lift before needing one.

 

ok thanks alot guys.

 

so i got my tires balanced and rotated and got a alignment done but the problem still continues

 

It's driveline vibes. You need an SYE and check your pinion angles.

 

I'd also add check out your trany mount..

I found that I had a vibe from mine, due to ripping it after my first real OffRoad outing..

 

cheap alternative to doin the SYE is a transfer case drop it helps to even out your driveshaft angles. i have a 3in lift and i had the same problem. i got a skyjacker t-case drop kit for $50 and solved all my problems