Hello all,

So, this has been plaguing me for a while, and I am looking for other poss ideas before I tear the t-case out.

Here's what I have: 2000 XJ, 5.5" RE short arm lift, 33" BFG AT's, D30 w/4.10's, D35 w/4.10's, 231 T-case w/SYE (new shaft, not a hack & tap, stock gearing), stock driveshaft in front, new shaft w/CV in back- both shafts have been recently rebuilt w/new joints, centering kits, and spin balanced. Pinion and t-case output shaft bearings seem to be good, no slop/grinding/etc.

The problem is this: Significant driveline vibration in 2wd at most any speed above about 40-45, particularly bad at 75 or so. It varies in severity between drive/coast/drag, but seems to be worst on drag. I can minimize it if I can hit the sweet spot between drive and coast, but still there. No noticable vibes on takeoff. Here's the kicker- take out EITHER driveshaft, and the vibration all but disappears, irrespective of speed. With both shafts in, engage 4wd, and the vibes are also greatly reduced, though not as much as with shaft out.

My thoughts were initially the drivelines, but I have been through both of them. The other possibility was a slight gear ratio mismatch in the axles, but I don't think so, though I have only verified the rearend ratio (will do the other) Beyond that, I was thinking output shaft bearings, but they seem to be ok. Any better ideas? Not sure what in the t-case could really even be causing it, but that seems the only place I haven't messed with yet. For the summer, I've been driving around with the front shaft out, but am going to need to get this fixed before the snow starts flying..

Thanks.

 

Sounds like the front output shaft bearing. Even if it's not in drive it's still spinning becauser of your live axles.
A guy from the local 4x shop told me about it and after taking off my front drive shaft my vibration stopped.
Instead of fixing it I bought a newer jeep! got lucky sometimes!

 

How's your tranny mount?
Crossmember drop installed?

 

Tranny mount is good. No crossmember drop, but the angles really aren't bad...

 

Hi I am new here and what u guys are talking about sounds like my xj. I get a bad vib at 40-50 km and then 75km and above.
I had the wheel bearings done and the driveline checked I have been told its my T case.... I have not done a lift yet... just have a set of pro comps but i even had them rebalanced... is it really the T case?????

 

Did you shim the rear axel to get your pinion pointing at your TC?
Mike

 

Beat me to it Mike.