Armycherokee

Ok so the problem started after I went mudding Saturday nite on our way back when over a certain speed I hear a whine but when I let off the gas it stops when I put it in neutral and rev it no noise but under a certain speed it's quiet but at a certain speed it's loud but when I go faster the sound goes away I have greased the ujoints and that helped a little but did not solve my problem what do y'all think

Firestorm500

You might have gotten junk internally into the rear diff.

Whining usually indicates worn gears. Grit could have chewed them up.

Armycherokee

Well the tcase was empty so I drained out what was left which wasn't enough to fill a small cup after that I filled with ATF+4 and went for a drive which helped a lot and the rear diff fluid is kind of milky not bad but still needs to be changed and the tcase fluid well what was left looked like used motor oil which tells me it was prolly stock from 92 it goes into 4lo easier now but that's another story