RX-Ben

My car has developed a diff leak and I noticed when I went to check the fluid level that there was a bit of outgassing/pressure release as I removed the fill plug (case was still pretty warm, about an hour or two after I stopped driving). Anyone noticed this?
Seem like the vent might be plugged up and pushing fluid past the diff/tranny seal - anyone know if the pressure is normal (like maybe it takes 2psi to open the vent)?

Thanks.

UstaB-GS549

I'm pretty sure that there is a vent on top.

RX-Ben

There certainly is a vent on top - just wondering if it is supposed to allow some pressure build-up or whether it is supposed to directly vent to free air.

drbenne

I change diff fluid every 2 events and there always is some pressure in diff that is audible when fill plug is loosened.

SteveDoten

Ben, every diff fluid swap I've done, I've noticed the 'hiss' when rem'ing the plug

www.rkt56.com

contact Rick for the best answer, he's a GM tech by trade and has built 100's of diff's

RX-Ben

Thanks Steve.

froggy47

Pretty common (expansion) to leak fluid out the vent. I change mine slightly warm & have not noticed pressure when I open, but real warm or hot could be some.

Don't know about any pressure relief metric.

Many guys just shoot it with brake clean & observe to see if it leaks again.

I fill mine till it dribbles & plug it.

I have seen some slight trace of fluid release on mine, but till it hits the ground I don't do anything but clean it off.

Cap'n Pete

I was experiencing this with my C6. Talked to a local race shop (who deal almost exclusively with 'Vettes) and was told that it's a common problem ... the vent doesn't work worth a damn, and allows a pressure build-up. My car had clearly leaked fluid from one of the axle seals!

Basically, the "solution" is to pull the factory vent, tap a fitting in there, and run a short hose with a breather filter on the end so it never builds pressure ever again. I never got around to doing that though, as I went and traded up to a Z06 instead!