Vibration between 60 to 72mph

[jeeptec]

2000 Xj. 4.0 automatic. 242 tfc. Dana 30/ 8 1/4 .I have a vibration from 60 to 72mph. It is somewhat oscillating. I noticed it after I lifted from 3 to 4.5 inches but at the same time in did rear disc brakes from a grand cherokee. An Aussie locker. I ordered and installed an Iron rock hack tap for my 242 tfc. A Tom Woods shaft set drive line angle no change.i found a bad rear pinion bearing . I did my gear swap to 4.10s. No change.took out front from driveline no change. Changed trans mount no change. Re balanced and rotated tires.no change. Set Tom Woods driveline back for Re balanceing.it had a bad ball socket. No change. Tried another driveline from another Jeep. No change. Install 2 degree shims to lower pinion and raise pinion. No change. I ran the jeep on the drive on rack using the air jack under the rear axle.did not find excessive driveline run out. Looked for grounded out engine mounts there worn but ok. Looked for exhaust sitting on body or crossmember. All ok. Not sure what to do next.

 

[yossarian19]

Remove the front drive shaft and see if it changes / goes away.
Assuming you don't have a hub kit on your D30, the whole front end is moving just as fast as the rear. You want to isolate which end is doing it before spending any more money.

 

[Anak]

I think he already did that:

took out front from driveline no change.

That is a puzzle all right.

 

[TheBlueXJ]

i would find out which end is causing vibration first. if its the 4 speed auto your at about 2000 if im correct determine weather it is motor mounts or not. what kind of tires you have cause i have 31 km2's and i have alittle vibration just cause of the tires?

 

[old_man]

Vibrations at higher speeds are most times related to driveshaft balance from my experience.

At this point, I would probably find a Bear Alignment equipped shop and have them do an on vehicle spin balance. High speed vibes can be caused by broken/slipped belt or out of round tire.

 

[1990JEEPXJ]

Have you tried removing the rear shaft and driving around? Does it seem more like a driveshaft which spins at a high speed or could it possibly be an outer wheel bearing?

 

[jeeptec]

Feels more like driveline type vibration. I reinstalled my Tom Woods driveshaft this afternoon but I installed it 180 from the marks when I pulled it out. The vibration is worse that way. The problem is I did too many modifications at once.im going to pull my hack and tap yoke and run it on my buddies lathe and see if it is true. Rotating the driveline 180 degrees tells me something is out phase/offset .

 

[redneck]

Did any of your shims get messed up when you pulled the carrier out to put in the lockers? I had a vibe from 74-80 mph and it was the gear mesh that was messed up after I pulled the carrier in my front TJ D44 to weld the sleeves in. When I pulled the diff cover I found glittery oil.

 

[jeeptec]

The 8 1/4 is threaded adjuster and it is a lunch box Aussie locker. I just rotated my rear Tom Woods driveline back to the marks I painted and the vibration has gotten much better. I am thinking the hack n Tap yoke maybe offset .