The lack of fluid is burn out from the rear end running so hot. Will boil the gear
oil into sludge and burn the rubber on all the seals as well. From what I have seen in the shops, this usually happens when the pinion nut is WAY over torqued, binding the crush sleeve and dragging the pinion too high on the ring gear. I doubt it was low or empty of gear
oil from the get go because you would have heard and felt it. Had anyone replaced the pinion seal for some reason? If not is was an assembly error. Just to be safe, I would run a high quality full
synthetic gear
oil (redline, Mobil1, etc) along the lines of a 75W90.