I own a 1966 Mustang convertible, 289 - 2V engine, with C4 automatic transmission. In July of this year I had the transmission rebuilt. After the rebuild the transmission is working and shifting as expected. Problem is transmission fluid leaks have appeared in areas that were not leaking before. In particular there is a nagging leak in the area where the bell housing bolts to the transmission case. It is a small seep of fluid when the car sits and more noticeable when the engine is idling.
Inside of the bell housing is clean so the front pump seal at the torque converter is not leaking. There is no leak at the transmission pan. There is no leak where the filler tube mates to the transmission body. There is no leak from the intermediate band nor the low-reverse band adjuster nuts on the side of the transmission.
Transmission rebuilder has removed transmission numerous times, installed new transmission pump O ring and there still is a small leak. Transmission shop believes the leak is coming from a small opening at the bottom of the transmission case where the pump seal O ring mates against the round housing.
I believe it is a passageway to the transmission pan. Can this opening be plugged without affecting operation of the transmission? I believe I have found posts that later model C4 transmission do NOT have this opening and the transmission pump does NOT use a round O ring for sealing. This makes me think this opening to the transmission is a poor design and can be plugged
Last edited by acarl1018; 11-09-2012 at 06:02 PM.
Reason: Add picture
There is a paper gasket that goes between the pump body and the aluminum main case. If that gasket isn't sealing, the fluid will go where you say it is going.
When I assembled mine, I put a small amount of sealer on both sides (can't remember what
type).
Here is a link to a picture of the area in question. I believe the paper gasket does NOT cover this area. There is an O ring that seals the round pump housing to the case and I believe the O ring is not sealing well. Design problem?
Can this opening be permanently sealed to prevent the leak?
Email Kenneth Collins at...... badshoe@myway.com .....with your question. He's the expert. He will answer you.
I have a PDF file that he sent me with a lot of his C-4 tips he learned from 45 years as a Ford Dealership Transmission guy.
Gimme your email and I'll send it to you.
Email Kenneth Collins at...... badshoe@myway.com .....with your question. He's the expert. He will answer you.
I have a PDF file that he sent me with a lot of his C-4 tips he learned from 45 years as a Ford Dealership Transmission guy.
Gimme your email and I'll send it to you.
I sent you a PM with my email address. Thanks for the help.
Did your rebuilder use an "O" ring, or a lathe cut seal. The proper ring for that location is a square cross section lathe cut seal. In the past, some kits have come with an incorrect "O" rings seal, and there have been instances of undersized lathe cut seals, also. If the seal does not fit snugly, gets twisted, or there is corrosion where the seal rides, you will get a leak. Check the groove in the pump body also. Any nicks or bruises there will also compromise the seal. Lastly, there have been instances of porosity in the case in the area of the bottom pump bolt holes. Use an oil resistant sealer on those bolts as a precaution.
Did your rebuilder use an "O" ring, or a lathe cut seal. The proper ring for that location is a square cross section lathe cut seal. In the past, some kits have come with an incorrect "O" rings seal, and there have been instances of undersized lathe cut seals, also. If the seal does not fit snugly, gets twisted, or there is corrosion where the seal rides, you will get a leak. Check the groove in the pump body also. Any nicks or bruises there will also compromise the seal. Lastly, there have been instances of porosity in the case in the area of the bottom pump bolt holes. Use an oil resistant sealer on those bolts as a precaution.
Don
Good points. I will ask the rebuilder about the style of O ring used on the pump circumference. Also will ask about leakage past the pump bolts.
This has been a problem for awhile. The "correct" '64 thru '66 Green Dot tranny gaskets have not been produced for some years. Once and awhile, They come up on Ebay. The correct "Green Dot" gasket should be almost a perfect square all the way around the inside of the gasket. The later '67-'70 Gaskets being sold have indentations on the inside "inner" square of the gasket. It is incorrect for '64 thru '66 Green Dot tranny, yet they are the only gaskets being sold and used. They are incorrect, and they cause leakage in the early "Green Dot" trannies. I gave up awhile ago, and just started making the gaskets myself. It is easy to do. Just by some gasket material, use the later gasket as a template, and when you get to the indentations, just cut past them on new gasket you are making...
Tony K.
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Tony Kovar
Melbourne, FL (Formerly from Long Island, NY!)
This has been a problem for awhile. The "correct" '64 thru '66 Green Dot tranny gaskets have not been produced for some years. Once and awhile, They come up on Ebay. The correct "Green Dot" gasket should be almost a perfect square all the way around the inside of the gasket. The later '67-'70 Gaskets being sold have indentations on the inside "inner" square of the gasket. It is incorrect for '64 thru '66 Green Dot tranny, yet they are the only gaskets being sold and used. They are incorrect, and they cause leakage in the early "Green Dot" trannies. I gave up awhile ago, and just started making the gaskets myself. It is easy to do. Just by some gasket material, use the later gasket as a template, and when you get to the indentations, just cut past them on new gasket you are making... Tony K.
Which pump gasket are you referencing that is incorrect in the repair kits? Square cut O ring that fits in the groove on the circumference of the pump assembly? Or the thin, flat paper gasket that seals the pump to the case?
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1966 C4 transmission pump leak
