2000 XJ 4DR: I6(72K miles), AW4, NP231,LP D30, C8.25
Whats been done: RC4.5" short arm/full leafs, Advance Adaptors SYE w/ TW driveshaft, 31-10.5-15 Wild Peak AT's, 15x8 (4.0 BS) Soft 8's.

Problem: 0-30mph a hard vibration seems to be coming from under the driverside front end, 30+ mph the vibration decreases.

Vibration was not present prior to lift and if the front driveshaft is removed the vibration is not present at all. Replaced all 3 u-joints in front shaft and still no difference. Shaft shows no signs of being damaged, missing weights, or bent. Shop did the alignment and steering is perfectly straight, no wobble in the wheels or steering wheel, does not pull to one side or the other when braking.

Tomorrow I was thinking of removing the rear TW shaft and replacing it with the front shaft and seeing how it rides (running no front shaft), then test it again with the TW shaft up front to see what happens.

 

did you rebuild the double cardon assembly in the front shaft? and how hard of a vibe? if its not that bad i would just leave it alone.

 

^ That's prolly your problem. You may be able to improve the vibration issue by adjusting your caster (tilting the pinion up a little to point straight at the TC. However, this might give you caster problems. I'd adjust it to tilt the pinion up a little and see how it does. If you can't correct the problem this way then you might start looking for a HP dana at the local pic'n'pull...

 

Yeah, says he replaced the 3 front DS u-joints.

 

Hey, this is actually my XJ. My buddy put this up for me but I decided it may be good to get my own profile. The vibration is pretty bad but it is worst from 15-35 MPH. Most of the other vibration problems I've read about get worse with speed or are death wobble. This one seems to smooth out after 40. I think it is probably driveshaft angles messing it up but I haven't measured yet. If that is the issue would a HP D30 make a big difference or would I be better off getting adjustable control arms and adjusting it that way?

 

Both adjustable control arms and a HP D30 would be ideal. If you had to pick 1, probably the HP D30

 

i bought my xj with 6.5" lift and a lp it had 0 vibes til i launched it whole different story, but what im saying is its not the axle its the d.s. angle buy adjustable arms and correct the angles. i had the same problem when i swapped to h.p. when i was dialing in the new angles

 

Yea but if he does that then his caster would be at a funky angle

 

^This.

You can try the adjustable LCA's, but there's no guarantee that once you made the vibes go away by getting the right pinion angle that the changes in caster angle wouldn't cause severe bump steer/death wobble.

If you were planning on getting adjustable LCA's at some point anyways I say go ahead and get them. Even if it doesn't fix the problem you were going to get them anyways, right?

Not sure how much an axle would run at the pic'n'pull but adjustable LCA's are going to run you about $200. Probably the cheaper and easier option to try first.

 

Theres no problem with the axle but the higher pinion would improve the angle without messing with the caster. I'm wondering if it would be enough, how much higher is the HP D30? Has anyone else had a vibe like this one thats worse between a range of speeds rather than just at higher speeds?

 

[QUOTE=ta2tony;2381797]^This.

You can try the adjustable LCA's, but there's no guarantee that once you made the vibes go away by getting the right pinion angle that the changes in caster angle wouldn't cause severe bump steer/death wobble.[QUOTE]

Thats what I'm trying to avoid, the steering and front end are great right now. Only problem is the DS vibes.

 

Im just sayin from someone who has a taller lift and had a l.p. your caster will be fine. Even if you buy a h.p. youll still need adjustable arms to eliminate all front driveline vibes. Or just pull the front d.s. and put it in before you wheel. Lol

 

I agree with getting adjustable arms. When I upgraded my vibes went away. I did switch to a hp30 later on but that was from destroying my lp and having one on hand. Also a great improvement.