Hey guys, I'm at my wit's end because I can't figure out why this keeps happening. My C6 in my 80 F350 w/400 and 4x4 keeps leaking from the pan no matter what I do. I replaced the pan because it was in pretty bad shape and I've tried using a gasket and I've tried just RTV but no matter what I do it keeps leaking. When l initially fill the trans with fluid and then shut it off and let it sit it seals, but once I drive it and get it up to temp then the seal fails and it starts leaking, and leaks constantly at about a drip per second until the fluid level gets below the seal. This led me to think it had a clogged vent and was building pressure, but I can't figure out how to get the vent out of the case to test it. It wiggles around like vents do but it is sort of hard to access so I can't look it over closely while it's in the case. Does anyone have any suggestions? I'm about ready to do a 4-speed swap at this point... Thanks in advance for any input.

 

Are you sure it's the pan? What I would do is get brake cleaner and clean it up really good, and then start it and get under there and watch it closely with a flashlight. If it seems to be leaking from the pan on the front pass side, I would suspect it might be the o-ring around the fill tube.

 

Sorry to high-jack but how does one go about replacing the o-ring around the fill tube? Does it just pull out and re-insert? My C-6 is leaking from the passenger side front corner, just as you stated.
I thought it was the pan gasket at that point even though it has a new TCI cast aluminum pan and new gasket. It seems to leak more sitting than running and more so if it is leaning to that side when parked.

 

Cole: What type of pan did you use as a replacement and what type gasket?

When I had a shift kit put in my C-6, the shop couldn't get the old beat up pan to quit leaking. They suggested a new pan but said that if I couldn't get an OEM Ford pan, then get a quality cast aluminum pan. They said the aftermarket stamped steel pans had flanges that were not stiff enough to seal properly. They also said to use a cork gasket, not rubber. I used a TCI pan.

I am still having some slight leakage but now think it might be the dipstick o-ring as Franklin2 suggested to you.

 

This morning I replaced that o-ring. I do believe that was the problem. I checked the servo cover and the shift rod areas but didn't even think about the fill tube and thought it had to be the pan. Fingers crossed that it's fixed now haha we'll see next weekend when I get home. The old o-ring was pretty brittle and dry cracked though. Thanks a lot for the suggestion Franklin I was getting pretty aggrevated with the situation.

 

I used a Spectre pan and I'm currently using gray RTV as the gasket, I'm usually a gasket guy but when I couldn't get it to seal I ended up trying RTV. Also as to your other question it is as simple as draining about a gallon(just a guess that worked) out of the trans, pulling the top passenger motor-to-transmission bolt, and wiggling the tube out. Replace the o-ring, lube it up so it will go in easy, slap it back together, and put the fluid back in.

 

"it is as simple as draining about a gallon(just a guess that worked) out of the trans, pulling the top passenger motor-to-transmission bolt, and wiggling the tube out. Replace the o-ring, lube it up so it will go in easy, slap it back together, and put the fluid back in."

Thank you sir. I will have to do the same as I verified that is where the leak is