What is wrong with my Jeep?! (vibes)

So I made a post a while back about some vibes my Jeep was having. They happened during acceleration and went away when my foot was off the gas. Turns out that when on jackstands, the back tires actually wobbled under acceleration. Scary.

So knowing it was internal axle problems and not wanting to fool with it... I took it to a shop. He found that the pinion bearing and carrier bearing were shot. He replaced those, and $475 later, my back tires still wobble and it still vibrates. Not as badly, but still WAY worse than it ever should. I'm a little pissed. But I don't know what to do... I have -NO- idea what's wrong with it.

Any ideas?

EDIT - Specs:
98 Jeep Cherokee Classic
8.25" rear with Trac-Loc
Tom Woods SYE and driveshaft
NP242 tcase
RE 3.5" lift w/full packs

...its been lifted with the SYE for almost 4 years, and it just started the whole vibe issue about a month ago. It always vibed a LITTLE on the interstate, but now it does it at any speed, so long as I'm on the gas.

I'm no expert, but to figure it out, people are going to want to know if it's pure stock or not. If not, what's been done to it. From my very limited knowledge it could be something as simple as balancing issues. Sorry can't help, but if you post specs, someone will have a better guess.

number one, your tires shouldn't wobble, so you have to find the cause of that before you go any further. Rotate your wheels both front to back and see if there is still "wobble". Wheel bearings? I assume that the shop would have checked stuff like the u joint and yoke? double check. work your way up the drive train.

Yeah, the shop said the ujoints and the yokes were fine. And he said there was a slim-to-none chance that the outer axle bearings were shot, which is what I thought was wrong, and why the wheels wobbled.

I don't know. In retrospect, I wish I would have just spent the $500 on a junkyard axle.