Hey guys I recently changed all my fluid and when I pulled the rear diff fill
Plug out I got hissing and air pressure came out. I didn't think much of
It at the time and then today after driving it I crawled under and wiggled the differential breather cap which seemed to be pretty tight on the breather and air pressure came out again. Has anyone else had this happen? Is it normal or was the breather cap possibly just stuck on there and now that it's loose again it'll be okay?

 

I'd replace it.

 

My diff does that as well. It has a brand new breather..