Rear diff leak / breather relocation?

Is there supposed to be positive pressure in our rear ends? I have a small leak where previous owner had repaired it him self or maybe someone else repairs it. Went on a 20 min ride and for 5sh min see bubbles coming out of the small leak. The leak is about a few centimeters away from the bolt hole on the back side of the rear end. I took the breather out and made sure it was not clogged, compressed air went through it easily but I did realize it does feel like it’s limited with the cap that goes up and down.. was thinking about putting a brass fitting in and extending it but would that change what Toyota originally engineered for this rear end? Thanks everyone I plan to drain rear end, hit it with a wire wheel where leaking, then completely dry it and use jb weld. And if possible extend the breather with a better source of venting

 

It should be slightly positive when hot, slight vacuum when cool, when the gases contract, I'd expect. You have the one-way valve in your hand there. Typically installed here, and it's only a $10 part for the OEM replacement. If you have that much positive pressure, given how rusty that diff and breather is, you may want to replace. But I'd consider a whole new, clean axle housing/assembly, personally.

​