Bad noise

Tranny or Diff, possibly brakes. Test it, Chock front wheels on both sides of the tires, jack up both rear wheels, Remove the driveshaft at the rear, leave it in the tranny, 2 people, 1 on each wheel, simultaneously turn the wheels forward. Will they turn? Now rearward, Results? What about hold one still, turn the other each way. Does the Diff Yoke turn? Other wheel held still? What about turn one wheel, does the other turn opposite (with a standard differential)(positive traction rear, both will turn same direction)?If things are not good, you may already suspect your brakes are locked up, depending on wheel movement, maybe just on one side. You might also check your diff fluid, maybe shove 2-3 inches of 3/8 rope in there, a little at a time and check each 1/2 inch as you go, this MAY sorta tell you how low you are, If everything seems fine back there, Insure You are still chockedENGINE OFF!With the tranny in Drive/ reverse/ Neutral, can you turn the driveshaft with your hands in either direction? Recently my Transfer-case (full of oil) had the tail shaft oil holes plugged up with what we think was Silicone Gasket, gobbed in by previous owner (swimming in there for a while) Mr. Jeep locked up at 55 MPH (this would be sorta a transmission issue on a 4WD) Came close to a rollover! This showed no signs, until it made a spinning noise, 5 seconds later, I was sideways in the other lane. IT GOT HOT FAST! SEE THE BLUE COLOR ON THE GOODIES! As scr. Ewed up as bearings, races, and tailshaft were (it torqued so hard it broke the transfer case's cast iron case) It would not move forward under power---IT DID MOVE IN REVERSE UNDER POWER, ABOUT 100 FEET INTO A PARKING LOT! Let me know what you find--Mega Detail is wonderful! I really hope it's the brakes!--The Medic