I think there are different kinds of caps used dependent on which end of the axle is concerned or perhaps if you are using aftermarket stubs. Anyway, one set has a single large bump which is round and the other set has a bump with five indentions to clear raised portions in the axle hub. Do you know which you need? I have one set or the other, can't remember which, but I can dig them out and check.
My axle and stubs are stock
If I remember this correctly, I had round ones on the stock axle, I ruined one when trying to pry it off, put the second one on the outer side, but it had clearance issues with the wheel hub shaft that the big nut goes on, so the shaft made a hole in the middle of the cover. So I installed the axle without covers. And then gaskets didn't stay in place and I started throwing grease around through the gaps. Grease would also get into the bolt threads and they started backing out. I kept tightening them, but on the second replacement axle I ended up stripping stub threads on numerous bolts.
I'm going to be replacing the rear cradle, diff side stub, and axle, so clearance should no longer be an issue. I need to install the axle the right way this time around. So I need one or both dust covers, I'm guessing round bump ones are stock, but the ones with five indentions should work just fine.
