Before you jump to conclusions about the transmission, drop the torque tube ball back and take a good look at the universal joint. A loose, badly worn U joint can get incredibly noisy, and a noisy rear end pinion bearing can transmit its noise up the driveshaft and sound like a transmission problem, also.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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