700R4 trans pan leak again and again and again - Hot Rod Forum : Hotrodders Bulletin Board
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Old 09-17-2008, 07:31 PM
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700R4 trans pan leak again and again and again

I put a TCI deep cast aluminum pan on my 700R4 using a black transgo gasket that looks like the GM gasket. It leaked, I replaced the gasket, it leaked again. I replaced the gasket again this time gluing it to the pan with Permatex aviation sealer. It lasted two weeks without leaking. Replaced the gasket again same method and a small bead of Permatex Ultra copper between the gasket and the trans, of course cleaning the trans pan rail off with brake cleaner. Let it set for day and a half before putting fluid in it. Didn't leak till I went on a 90 mile round trip to a cruise in. I have never had a pan I couldn't seal till I met this one.

Any ideas?

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Old 09-17-2008, 07:36 PM
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Try a cork gasket and NEVER use silicone on a trans. when any of it breaks off and hangs a valve it won't shift. I have used weather strip adheasive for 20+ years without any issues and only glue the gasket to the pan torquing it down to 80-100 inch pounds.
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Old 09-17-2008, 08:01 PM
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Quote:
Originally Posted by Overdriv
I put a TCI deep cast aluminum pan on my 700R4 using a black transgo gasket that looks like the GM gasket. It leaked, I replaced the gasket, it leaked again. I replaced the gasket again this time gluing it to the pan with Permatex aviation sealer. It lasted two weeks without leaking. Replaced the gasket again same method and a small bead of Permatex Ultra copper between the gasket and the trans, of course cleaning the trans pan rail off with brake cleaner. Let it set for day and a half before putting fluid in it. Didn't leak till I went on a 90 mile round trip to a cruise in. I have never had a pan I couldn't seal till I met this one.

Any ideas?
Is it in fact trans fluid you are seeing? Check other seals too, the trans pan is the lowest point to drip from.
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Old 09-17-2008, 08:14 PM
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Check the pan for warpage and flatness. It is probably a Chinese pan and is not true.

Vince
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Old 09-17-2008, 11:08 PM
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Some of the cast pans had a problem with leaks where the shift cable bracket bolts to the pan. For some reason fluid leaks through the bolt threads. This was on the Hughes cast pans which look just like the TCI pans. Use some Teflon plumbers paste or the gray RTV for aluminum on the threads & see if that cures it.
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Old 04-06-2010, 06:38 PM
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I hate to bring back a old post as old as this but hate to leave it unresolved too. Doesn't seem to help anyone then.

To make a long story short the pan, as many of you suspected, was not the leak. The problem goes all the way back to the guy that built it in the first place. The rubber seal that seals the TV cable into the trans case was bunched up on one side and whenever the fluid would expand from heat or just the sloshing around the fluid does in normal driving would leak right past it and appear to be the pan gasket leaking as it would follow the pan rail all around after parking.

Because it is so hard to see up that side of the trans we had to remove the exhaust and drop it down a bit to see anything. We then dropped the pan and removed the TV cable from the trans and that is when I found it.

Finally.

The guy that built it must have had his head up his, well you know.
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Old 04-06-2010, 07:09 PM
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I've seen many "pan leaks" that were not.. I have near given up telling folks to check all locations.

I went about 5 rounds with a friend a few years back over the phone and his "pan leak". It was the shift shaft seal on the t-350. He had changed the pan gasket , the pan , the gasket again

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