when i did a trans swap, couldn't pop it out of the case,
i ended up taking the trans out with the drivers axle still in the case....yes, it sucked, almost didn't get it out, but i managed....
i think a combination of the car being jacked, the car over a stand below pit and having a overhead 4-way chain hoist made it all possible, anyways...
once the case was on the floor, took a 20lb slide hammer and popped it out.after trying a pry bar and a sledge, and taking pieces out of the case...
comes to find out the snap ring was out of center on the axle shaft, and got wedged in the spider gear, and it actually cut spline grooves in the snap ring.....
physically no way i could of done it with it in the car, just couldn't get enough force in any position.
anways, yeah, a solid constant push, and a tap on the hub end, and it'll pop into place, use some thick heavy grease to keep the snapring from moving around, as it needs to be dead center to not hang up and give problems, like i had.
if you've ever had a transaxle apart, you'll understand how the spider gear is shaped for the snap ring to slide in and snap out. They go in *ALOT* easier then they come
out.
btw, what do you mean by don't have both axles out at the same time? how would one easily replace the gearbox?
and it doesn't matter 10 years or 100 years. unless the inside of the transmission gets rusty (doubtful) they'll slide in and out of the spider axle gear like butter. it's the snapring that gives problems.
I've done 12 or 13 transaxle jobs, always reused the clips if they weren't chewed up like my example was.