If you are not familiar with how all this works you might want to take a look at factory overhaul manual.
http://67-72chevytrucks.com/vboard/s...d.php?t=558016
Look at the cross sections and the entire gear setting proceedure. To answer an earlier question an axle simply slides into the differential side gear splines. While this also wears in to some extent it has nowhere the velocity or motion of a gear set.