-Depending on what you have, just use a hammer, & a nail set/tap, & set it on its side, (leave room for the axle to shoot out the other side). Be sure to hold it together, & watch the order the internals mount on the rod, it goes all the way through the diff., etc.
-if you want to be able to remove the tires/wheels, (anytime), you should be able to tap an all-thread rod straight through, even as you're removing the stk. axle rod, then put on 2 locknuts, & set it aside & take a breather