i believe you have the wrong or misboxed axle count the spline check diameter ratio
hoanestly id find a manual onling just google your car year make and your type jsut add manuals after youll get the correct manual you can get a book orderd or get a printable version off there they may be free or pay by pay pal or a similar sight id suggest getting a book one due to the fact youll have it on hand incase you are a do it "yourselfer" youll be able to look up part numbers and such in there good luck
When I replace the axle halves, I run the Nut off till it is level with the shaft end. THen take a piece of wood and set it across the shaft and hit the wood with a hammer. Usually only takes one or two hits and pops right out.Then I remove the nut and finish removal . Hope this helps, Good luck and have a great day.
go to a junk yard as it'll be a lot cheaper there... Yes, technically you can just replace the backing and mirror. The backing is connected to the housing via two rods and some clips. The rods are (secured to the backing and these adjust the pitch of the mirror). If these rods become separated, then it may be tricky to adjust the mirror. Then again, adjust it once and it should stay