Yay! Page 2. Thanks for keeping it alive, guys.

Always remember the previously-mentioned stick-a-magnet-in-the-hole trick to make sure you don't have any foreign junk up in there obstructing your pristine new axle. I've pulled a whole snap-ring out of a transmission like that once before. Make sure nothing's in there already that's not supposed to be.

If the hole's clean and the retaining clip looks okay, jam that sucker in there while twisting. Sometimes it takes some jiggling... but just don't beat on the axle with a hammer or anything like that. It should slip into place.

I have seen bad retaining clips on remanufactured axles, but that's a rare occurence. Used axles, anything goes.