VAXJCOUNTRY

I've been reading on here about replacing u-joints....thats going to be the next thing I guess. My lift is a 3in procomp in the front and a S-10 bastard pack in the rear. I'm using JK Rubicon shocks and have a Rusty's t-case drop installed. I have an on-throttle vibration that starts around 35mph. If I let off the throttle it stops. The harder you are in it the more it shakes. You feel it in your as$, not in the wheel. I'm guessing the bastard pack being at least 4in of lift is likely the cause? Not enough compensation in the t-case drop? Should I add more washers to the t-case drop and push it down more? Shim the axle? Someone told me I could not use shims...I always thought you could shim a solid axle rear? Its a n 8.25 corp rear end. Halp! Oh, I've also been told it is normal and just live with it... "out of balance driveshaft" as he put it.

DEVILSTOY

maybe its the drive shaft ? when i had just my 4" lift on i didnt even have a transfer case drop and i had 0 vibes

VAXJCOUNTRY

It always had a very slight on throttle vibration...maybe the lift and the 31's just accentuate it?

DEVILSTOY

yea if it was always there , you would deff feel it more with the lift and bigger tires , you can try either grabbing another drive shaft from a junk yard for cheap or take your and get it balanced , or even take a look at your rubber tranny mount , it might be shot

djlarroc

Tranny mount is a good idea. Mines was shot. Also, check your motor mounts. My xj had terrible vibes when I bought it, and it was a broken motor mount.

We just did a 3" lift on my friend's 98 xj. No vibes.

PolarXJ

Can you tell where the vibrations are coming from? If not, try removing the front drive shaft, if the vibrations persist, replace the front and take out the rear (4 hi to drive). Oh, is there a pulsation to the vibration? This would also indicate that its a driveline vib. Just because the driveline vibrates, does mean that its out of balance. By adding a lift you change the pinion angle on your axles. Grant most XJs with a 3" lift don't get any or minor vibrations at higher speeds, but the pinion angle is a possibility.

VAXJCOUNTRY

Well, took a ride with a tech over lunch. Said that the vibration is driveline in nature. Its more like you hear it then feel it really. Pulsation might be a good word for it. He seemed to say I should check the driveshaft angle first to see how out of spec it is. Like I say the back lift is more like 4-4.5in.

PolarXJ

The back being more like 4 to 4.5" I would bet that its the pinion angle.

VAXJCOUNTRY

I didn't take measurements from stock (wish I would have) but I have never seen a 3in kit where the rear was even level with the front (an AAL kit). Mine the back sits up well above the front. There is a back to front downward slope. Its got to be at least 4in. Springs were from an 88 S10 long bed 2wd.

dudels99

pinion angle for sure

BlueXJ

Try a set of shims to raise the pinion angle and a new tranny mount. If those cheap fixes don't do the trick then the next alternative is a SYE.

VAXJCOUNTRY

Ok, where do I get shims at? Are they just an autoparts store thing? I'll let it knock and vibrate before I do an SYE...to much loot

bender9406

I have the same rythmic hum/vib... at 30-35mph and 65+ mph. Same symptoms?

I have a 2001 Cherokee Sport... it did this before the 2" lift.

Jamie57

Try what PolarXJ said first.
It's free it's easy.
I had a similar problem and it was the ball in the Cardon joint on my front shaft. Can't see it until you take it apart. It's also why I got my jeep for so cheap. Original owner was sure it was a real serious problem in the transfer case.
TRY IT FIRST!
Yes I'm yelling. You'll kick yourself seriously if you spend more money on other stuff and find out this was the problem all along.