Trying to help figure out another persons trans problem. It is a fresh 727 put together by local trans shop.All the good stuff done as in billet drum,low gear set, rollerized output support, low band apply brake. Has a problem with fluid coming out of the relocated vent on rear of the case after car idles around the pits. Even added extension tube to bring it up 18 inches or so and it still does it. Pulled the tailshft housing to double check location of vent correct per instuctions. Any ideas?

Is this where they put the new vent?

Yes.

I wonder if the gasket is sealing off the bottom of the passage (the rib under the drill bit). Then the cavity could fill with fluid from the top and go out the vent. When I did mine, I ground a little better drain slot in that lower rib behind the rear support, but left the rib for splash protection.

It looked like that could happen so when i had the tail stock off I drilled a 3/16 hole in the rib under the vent thinking the same thing. Then I threaded the hole for an 1/8 tube fitting so he could run a solid tube up the back of the case to be sure it wasn't just sloshed up the vent. I cannot figure how it could be pushing fluid up that much tubing but it is. It is on a Hemi A- body with a blanket so it is a P.I.T.A. to pull.

i chased this problem last season too. for the life of me i couldn't work out how so much fluid could get up in that area. the gasket almost acts as a splash shield & yet i was probably loosing an ounce or 3 every run.
i ended up making a new vent on the tailshaft & extending a hose up towards the firewall. at the end of the hose i fitted an old 3/8 fuel filter to act as an expansion chamber. this would allow the system to "burp" the air bubble out without spewing the fluid in the line in front of it. to top it off i have a mini K&N style filter fitted to the outlet side of the fuel filter so it don't look so agrigcultural.
with this mod, any fluid that comes out the vent now gravity feeds back into the trans on the drive back to the pit. sure makes it cleaner to climb under the car these days.

I wonder if transmissions with this problem (and this vent relocation) might be due to the rear support not laying flat on the case and spraying fluid from the cooler return line at the vent?

This won't help your problem, but the next trans brake I install, I'll drill the relief hole in the piston, instead of the drum. I think that's a Tranzact idea. Is it hard to fill, as if it's not venting?

are the govenor weights pulled if so have you taped and pluged the govenor feed port of not it will spray out of the vent


good luck

Yes the weights are pulled. The last groove in the housing for the park pawl sticks out of the roller support and doesn't have a seal ring on it. Would a rev/manual/brake valve body even pressurize that circuit? I guess I will call the support manufacturer and see what info they have. Also did put a clear filter pointing up on to stop the flow for now. Thanks for the input so far. will look into the govenor issue next. JB.