after living in NY for 6 years and knowing how the salt turns nice trucks into old trucks fast there, might want to take the time to pull the third inspect the gears...
only takes 30-45 minutes to pull...
as far as the leak, I think Jay is on the right track as far as overpressure pushing diff oil out.

-in your first post you mentioned you used pliers on the diff breather (unless you were referring to the cap that should have just moved around on it's own)..in the future try a wrench...

 

Exactly what I was thinking Jay, I am gonna pick as much rust off as I can and see if I see a hole. Then I'll spray the whole thing down with brake cleaner and see if it starts to seep again. If I find it, it will be JB Weld to the rescue.

ocdropzone......yeah I meant I was using pliers on the breather cap. It was rusted closed, wasn't moving around on it's own at all. I sprayed it down with PB and lighlty used pliers to twist it, to see if I could loosen it up and get my diff breathing again. But as soon as I touched it, the cap popped right off, and I got that hiss from the diff, so now I know it's breathing. Just gonna throw some vacuum hose on it.

Gonna change out my diff oil also. Anybody have any preference's? I think I have some Penzoil GL-5 laying around.