Regular cab lift vibes

Little backstory here, I've had my lift on for about 15k, and I've had vibes at 40 mph, so I swapped my rear driveshaft around, then it went up to about 70mph. I was fine with this for awhile since I usually don't drive on the highway.

Fast forward to about 2 months ago. I swapped out my clutch for a heavy duty LCE clutch.

My son was helping me, and the transmission slipped of the jack and landed on me, then rolled on to it's side and smacked the front output shaft on the transfer case pretty good. (I was fine surprisingly for catching a 150lb+ transmission and transfercase). Button everything back up here's where things get odd...

Vibes are now RPM based, and happen mainly when lugging the truck at around 2k rpm in a high gear at low speed. No more vibes at 70mph, on the highway the truck feels great.

So I keep driving it, swap out the transfer case fluid for some heavier stuff 85w-140 severe gear lucas oil. Doesn't really change anything. Try flipping around the front/rear driveshafts -- no change.

So at this point I'm thinking I screwed up the bearing on the front driveshaft output shaft in the transfer case.

Go offroading on saturday and really run the truck hard. Lots of mud, lots of water crossing. On my way home I notice the vibes are damn near gone. Practically non-existent.

I can't logically figure out wtf happened other than the truck was just begging for a good thrashing and was getting upset with me over not taking her out for a run in the mud....

If I do need to replace bearings in the transfer case, I'm assuming that's a pretty bitchin teardown job. Anyone ever done it?