I am hoping that someone can point me in the right direction. I have searched for days on the forum for an answer. I am experiencing a vibration starting at around 30mph and it continues with speeds higher, but does not exist slower. It only occurs when I am accelerating or on the gas at constant speed, it goes away while coasting. I just installed 4* shims in an effort to raise the pinion and reduce the angle between the driveline (8.25 rear end), but that did nothing for the vibration. That angle is currently at 2* between them which should be good. The lift, driveshafts and wheels/tires are all brand new and the transfer case was just rebuild with a SYE. The vibration occurs in 2wd but seems to go away in 4wd, however I have not taken it up to higher speeds yet in 4wd.

Current set up:

2000 XJ
NP231 Transfer case
RE 5.5 long arm lift
SYE with Tom Woods front and rear driveshafts
Wheels and tires (33") are brand new and balanced
Serious Offroad UTK steering

I currently live in Buffalo, NY and would consider taking it to a shop if someone can recommend one. I just took it to Quad 4x4 (formerly United 4x4) and the only thing they could recommend is a custom lower transfer case mount on the new RE crossmember. They checked the play in the rear pinion and all the U-joints. I am starting to think it might be the rear driveshaft being out of balance even though it is brand new from Tom Woods.

If someone with the same lift or same size lift can help I would greatly appreciate it, I am going crazy!!

 

Pic of rear shafts angle would really help us help you.

 

Check out this webpage it will give you a place to start.

http://performanceunlimited.com/docu...tionguide.html

 

Missing any weights off the driveshaft?

 

I will post pictures tomorrow of all the driveline angles. Would it be worth having the balance checked on the driveshafts even though they are brand new?

 

How does your steering react? Is it affected differently turning vs straight? Have you checked every bushing? Motor mounts? Trac bar?
Did you have this vibration before the lift?

 

The steering from SeriousOffroad is amazing and is not affected. There was no vibration before the lift. I have checked the motor mounts and trac bar. There is no vibration when I am coasting, it is only when I apply the gas and place the driveline under load. It is worst between 35-45mph under load and then starts to decrease. It just so happens that I do most of my driving between those speeds.

 

Here are the driveshaft angles. The front pinion could need to be raised slightly, but considering when the vibration happens I doubt its the front driveshaft.

 

I still need to make a trac bar adjustment since the front axle is not perfectly centered, but the bolts are torqued to spec so I doubt thats the reason.

 

Take the front shaft out and drive it, if its still there take the rear shaft out and put the front one in and drive it. At least then you know if its front or back.

 

I bought a new RE driveshaft that needed a new joint and had to be straightend and rebalanced.