Well, I can still put my hand on the diff after 30 mile commute including 20 miles at 59 MPH so it isn't getting TOO hot.
Total miles on unit= 200 already
Noise is still present, but no louder, maybe a bit quieter.
Thanks for the encouragement and the gear oil recommendations. But how many mini-trucks run 5.29 gears? Those are pretty steep teeth!
The sound persists and yes, my rear driveshaft slip yoke is pretty much cashed and my pinion angle doesn't quite match my t-case angle, and I watched my driveshaft spin while up on jackstands and the slip yoke appears to be put on the driveshaft at a slight angle (It just doesn't look right going round 'n' round!) Maybe the yoke is bent or heat warped. so yeah, that might be part of it, but it sounds like pinion bearings.
Since I have not yet burned up the diff, I think it is going to be just fine.
Asked my dad, "The RudeMaster," and he says, "Build a whiner and it will whine forever. It might just be the gearset. Buy a commuter car."
At 500 miles I'm going to go synthetic. not sure what weight yet, but it would appease my psyche to have something in there that can handle higher temps without film failure. In the race car world, we'd see a few diffs burn up a year on conventional oil. 1/year on mobil 1 and never burn one up with redline. Why?