8 3/4 axle lube change

The vent is basicly a bolt with a hole drilled thru it and has a tin cap with rubber seal inside pressed on top to keep dirt and crap out. It allows for expansion of the fluid in the rear housing. They can get crusted with dirt and crap and then not function the way they were meant to causing axle seals to fail or seap. One word of caution when working on it, DO NOT over tighten it when putting it back in, it can/may break very easily and then good luck finding a new one. I had a buddy helping me with my car a while back and he was putting the vent back in and broke the damn thing, I ended up tig welding the two pieces back together because I was unable to locate one localy.