When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Have 71 convertible, base 350 with 3 speed automatic transmission. The transmission is a TH400. Whether running or sitting I am getting heavy leaking toward the front of the pan or so it seems, right where the flywheel dust cover/Bell housing meets. I have put on new cork gasket, no luck. Tried the rubber gasket, no luck. Even used Loctite Gasket Eliminator and no luck. I feel like the original pan is in good shape to confirm.
What am I overlooking?
Could it be coming from somewhere else?
Any and all help would be greatly appreciated.
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
You have to get under your car and inspect everything closely to pinpoint the leaks.
The PSCV or the cylinder might be leaking or one of the four rubber hoses, or it could be leaking where the filler tube meets the pan, or it could even be the transmission cooler lines or any of the rubber hoses on the ends.
I agree with AKjeff and J. On my '72 with 85K miles my TH400 was leaking from what seemed like the front of the pan. I also tried a new gasket, then a new pan.
Nothing worked so I finally brought it to a tranny shop. They pulled it, replaced the input shaft seal (that was the cause of the leak) and rebuilt it.
No more leaks from the transmission, however now I have an oil leak, I believe my rear main engine seal was disturbed.
I should of thought about having it replaced when the transmission was out of the car.
Oh well, one thing I've learned with this car after 42 years of ownership is that there is always something to fix.
I wonder how hard it is to replace the rear seal on a 454.
As for the pan…the next time you remove it lay it upside down on a granite countertop. You may be surprised how warped the sealing areas around the holes are.
Transmission fluid leaking need help
