hole in top of right side rear axle assembly

[flyboytroy99]

Stupid question #1 for the day. '71 GT rear axle assembly. What purpose does the small hole on top of the right side of the rear axle assembly serve? It's on top, about half way out the right axle. Thank you.

[spdkilz02]

i would say that it is a vent for the diff.

[bq97]

It's the breather hole, there should be a small one way valve on it. It's purpose is so pressure built up inside the rear end doesn't force oil past the seals.

[flyboytroy99]

That makes sense. The check valve is missing. Any ideas?

[flyboytroy99]

Two questions come to mind immediately. #1) Is the check valve replaceable? And #2) Is it likely there's a nut used to hold the check valve in place that is now somewhere in my axle enclosure?

[bq97]

The valve screws into the treaded hole, there is no nut on the inside of the axle housing. I just checked both of my spare axles and neither one has the valve maybe someone else has a spare they can send you or you can call Opel Gt Source. They should have one.

[flyboytroy99]

BQ97, you are the Rear Axle Breather Valve Buddha! Thanks for the info.
P.S. I'm so glad I don't have to open this thing up in search of the long lost nut!

[GTJIM]

Most RWD diffs for GM cars have some sort of breather so a search through a junk yard should find you something that would work. The tiny valve is there to vent any pressure build-up ... and keep the water thrown up on wet roads out of the diff - so it is quite important.