If your rear end was over full at one time and you have done nothing to correct it, it will likely repeat this phenomenon in the near future. The transmission supplies the universal joint with lubrication through the output shaft area. The only way this transmission oil can get into the rear end is through the front pinion seal. An Okie bushing/seal will fix this.
I suppose a guy could add gear oil to the transmission, and drain oil from the rear end on a weekly basis to keep everything operating properly.
Carl
