Rear Axle clunk

[lxe4]

Tried a quick search, sorry if this is a well known deal. My right axle shaft slides in and out of the housing about 1/4''. I've let it go for a while but I'm starting to think I should pop the cover and figure out whats up. The left one is pretty tight. 96 14bolt 9.5 semi float 8 stud 13'' brakes.

I only recently found out from here that I'm not supposed to have friction additive in there, but I do. The Guv lock lost its locking action many moons ago but I wonder if I change the oil if it will come back. Mostly I'm wondering if the axle shaft is going to depart with my 6000# trailer pushing me.

I should just pop the cover and sort it out, I guess I'm just hoping to have parts on hand before I open it up and imobilize myself

Thanks