Rear Axle

Exactly. It is kinda like tightening your front spindle nut. Same principle. Two tapered roller bearings at each end. The only difference is the bearing tappers are reversed and the "nut" (adjustor) pushes on the bearing race instead of the bearing itself

I usually put the non adjustable axle in and tighten the retainer. Then put the adjustable axle in with the adjustor backed off and the retainer tigthened down. Take a sledge hammer and a wooden block and give a light whack (not too hard!!! don't want to break the retainer) to the center of the adjusting side axle. This will seat the bearing races in the housing. Then start adjusting until you can just pull the axle back and forth a little. Use a long punch and a hammer to do this. I think the spec is 0.008"-0.020" end play. But you can do it by feel. Don't forget to put on the lock that goes under one retainer stud.