I installed all new u-joints and a new rear drive shaft when I did the sye. Weather has been crap all weekend so I didn't get a chance to mess with the Jeep. When I get back into town I'll give it a once over to see if I can figure out my issue.

 

I had the same issue and I had just gotten a new long-arm, regear, F&R lockers, new front and rear adams driveshafts etc.

my front pinion angle was set very low. I adjusted the upper control arms a bit longer and it took care of about 95% of my vibration issues. Now I think the rest is just mud terrain tires.

 

I'll keep that in mind. Probably pick up an angle finder this week and check the front pinion angle when I'm checking the Jeep over this weekend. I was looking at the front pinion while I was waiting for my clothes to dry at the laundromat. It looks to be off a fair bit.

 

I had my driveshaft done by a professional shop that was recommended by a truck repair shop. Had the exact same vibe problems as you. Had tires balanced and still there. I have two sets of wheels (235x75's for street and 31's for off road). The vibe was definitely worse with the smaller tires so my attention went right to the DS. Put rig on jacks and let it run in 4th gear and crawled under. Wobble was noticeable at pinion end. Took it back with video from my phone to shop. They re-worked and I put it back and still have the problem and once again got under it running and still see a smaller wobble. Looking for another solution myself as I'm not dealing with this shop any more.