TheJerm

My specs:
3.5-4" lift up front
~4-4.5" rear
-bastard pack
-RC shackle at 1.5" lift setting (rides much better)
-3 degree shim
-shim caused the pinion and DS to be almost in line.
Thats about all to my lift, oh and i did the shim cause it ate up my rear ujoint in about 1yr.

I lifted the rear alittle bit with the shackle to take out the sag from the bastard pack i built last summer. Now i get driveline vibes around 30mph but i still can go 80 with no problems. I just dont understand why it only vibes at 30mph.

Any suggestions?

TheJerm

Nobody has anything on this? I'm going to make my own tcase drop to see if that helps.

I just dont understand why it would do it around 30mph but not at higher speeds

TrekkerJmm

I had vibes from the rear DS also and put in 6 degree shims and a 1 inch TC drop and the vibes went away...Tj

98jeepster

I have the same problem mine is the slip yoke the lift ulled it out a little and it gave it a little room to move a little and vibrate jack the rear diff up and runn it to thirty and have a buddy look under it to find where its coming from exactly

lolz_jeep

well guy most likely what your issue is are unbalanced tires this comes out between 30-45 mph but after 45 they harmonically balance them selves.

you might also want to check for play in the rear drive shaft and consider a SYE kit there is also the deadly DEATH WOBBLE witch comes from bad bushings on your trac bar or control arms

98jeepster

Yea I know mine is the slip yoke bc I just balanced these tires and I have a brand new lift and it started after the lift and I jacked it up and ran it and found out exactly where the sound and all was coming from

neeland

Just did a 6.5 rc long arm a couple weeks ago. Had a give from 29 to 32. Sye went on this weekend an the give is now gone. Get an sye before the transfer case is shot. Not saying it can't go without for short periods of time but in the long run ur asking for trouble. Just my opinion. Atleast get a hack n tap.

Jeepxj1234

I have a 3" lift and had vibes only around 30 mph as well. 2* shims and a tcase drop did the trick.

98jeepster

Yea that will probably work for him

TheJerm

Yea i fixed my vibes with 1" tcase drop, dang 4.5"+ lift came up on me quick (I remeasured today while still light out). Pretty sure i had vibes because i used a aw4/d35 DS in my AX15/c8.25 which cause it to be alittle to short. I'm not happy about it but will hold me off till i get the money for a SYE.

At 4.5" with a SYE, can i use a stock front XJ ds? or does it really have to be changed alot? I have several DS's but they are 700 mi away right now.

PJsJeep

front drive shaft will work