One thing I found today while running it was the driveshaft is extremely warm near the tail shaft of trans, but at the differential is cool.
I would pull the shaft & check that the front yoke/ ujoint moves smoothly back & forth in both planes. pull the rear ujoint caps & how much end play the front yoke has into the trans (I like no more than 3/4"). extension housing rear bushing play. If all good I would swap in another pig (non sure grip/any ratio) what ever you have laying around to confirm/elim that. is the backlash OK on the one that is in there?
