So I jusy pulled the transmission in my 04 lancer. Installed new differential bearings put everything back together. But now got a problem the drivers side axle won't go back in. Pushed on it hard hit it with rubber mallets everything. Splines all seem good took the clip of still won't slide in. I'm out of ideas now.

 

If it won't go in with the axle circlip off, something is very, very wrong inside that transmission.

 

To update this I was able to get it in. Turns out the circlip created a burr
On the race where the axle goes in not allowing the smooth fat part of the shaft to slide in. I cleaned up the burr with some emery cloth got a new circlip and in she went.