Well it figures. We meet up with Ken and now I have his bad karma...
After a long day on the trail, coming home I noticed ( as did my passenger) the rear of the truck is fish tailing when I come off the gas when at 35+. Very pronounced at 60+mph. Lockers aren't engaged of course and the TC is in the right spot. Just changed all fluids about 1500K ago and everything "looked" fine in diffs and in TC.
The suspension seems straight. No banging or other noise. No gear whine. Everything looks and feels tight.
Any ideas? The only thing original on my truck at this point is the TC. But it seemed to operate well all day on the trail.