I got my new rear end in completely today. The brakes that came with the new rear end were all rusted and broken, so I used the old brakes that work just fine. When I finally went to put on the drum, it wouldn't go on the whole way- the circled part in the picture wouldn't fit through the center hole of the old drums. Can anyone tell me why? I don't know what year the new axle is. I really just know it's an 8.8.

I'll probably just end up using the old axle shafts again if I don't think of anything else.

Not sure what that part of the axle is called

(not my picture)