THM 350 Gasket

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Jul 26, 2016 | 05:15 PM

SwampeastMike

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Melting Slicks

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From: Cape Girardeau Missouri

THM 350 Gasket

So much for my leak-free '79 L82...

Was out of the country for a couple months and there's a slight leak from the transmission pan gasket. I recently replaced it and the only kit available in town had a thin rubber gasket. Mating surfaces were spotless before I installed and I've already torqued above what was specified in the kit.

Any suggestion for a good quality cork gasket?

Jul 26, 2016 | 06:26 PM

SH-60B

Melting Slicks

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From: Meriden CT

Did you check the flatness of the pan before you replaces it? Sometimes the rail at the bolt holes gets dimpled and leaves gaps between the holes. Not an answer to your question, but......

Jul 26, 2016 | 06:46 PM

SwampeastMike

Thread Starter

Melting Slicks

Joined: May 2015

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From: Cape Girardeau Missouri

No, I didn't check for flatness. Are good quality precision steel rulers suitable for that test?

Jul 26, 2016 | 07:14 PM

SH-60B

Melting Slicks

Joined: Mar 2008

Posts: 2,989

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From: Meriden CT

Oh yes. I have Starrett from all the way back in my apprentice days, lol! But any straight edge will do, framing square, level, etc.

Jul 26, 2016 | 07:29 PM

mikem350

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From: Sunrise FL

If still a problem, I would clean all the surfaces with brake cleaner and check again. My leak turned out to be from above the pan, was the shift lever gasket.

Jul 26, 2016 | 08:14 PM

cobrachuck

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From: SW Ohio

I had several leaks from sitting 19 years the 1 st was the vacuum modulator then the pan. Use a strong light to get a close look.

Jul 27, 2016 | 11:01 AM

Joe Papa

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Joined: Dec 2013

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From: Pacifica CA

Check the selector shaft and dipstick tube seals.

Jul 27, 2016 | 12:08 PM

SwampeastMike

Thread Starter

Melting Slicks

Joined: May 2015

Posts: 2,365

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From: Cape Girardeau Missouri

Thanks all for the suggestions. I replaced the modulator valve at the same time as the filter and gasket. The old gasket was leaking as well. Will check the selector shaft and dipstick tube seals but am almost positive the leak is from the gasket.