There is a big nut holding the rear yoke onto the driveshaft at the bracket that attaches to the crossmember. Remove the nut, change the bearing and seal, and reassemble. Item #13 in Bill's diagram is the seal that's causing the problem, but you should also change the ball bearing while you're in there that far. I'd suggest using a permanently lubricated sealed bearing, instead of the original design that probably has to be greased periodically.
Jerry
