Duster 360 *Snuffy* New exhaust and 8 3/4 !!

That is a pressed on retainer. The bearing is pressed on and so is the retainer. Just try to press them both off together and see what happens. A 10 ton press can't do it. You have to cold chisel the retainer off first (don't want to heat the axle) and then press the bearing off. Since there really are no in and out loads on an axle shaft like that there is no way it's coming out of there.