There is a seal built into the bushing at the front of the torque tube. "Okie" is a term for a replacement bushing built in Oklahoma that could be installed without disassembling the whole rear axle assembly. If the seal failed, transmission lube could run down the torque tube and overfill the rear end. Yes, the U joint and front bushing is lubed by splash from the transmission. Some transmissions have a pipe plug above the U joint where a little gear lube can be added on occasion to assure that the U joint gets adequate lubrication.
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!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!