Moroso TH350 Pan Gasket Woes. Can't Make it Stop Leaking!

Discussion in 'Transmission & Driveline Topics' started by slayer021175666, Feb 2, 2021.

  1. Bentley

    Bentley Veteran Member

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    Are you using any sealant on the gasket?? I watched a very informative video about a month ago, done by Fel Pro, and the gaskets they showed are NOT designed to be used with any sealant. One of them was a one piece pan gasket... The Fel Pro guy said it makes the gaskets too slippery and they will not tighten down, but will tend to "squish out" to one side or the other.....
     
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  2. budro6968

    budro6968 Veteran Member

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    I would say not to use RTV type gasket sealer. A piece could break loose and make your day worse. Several pans and the same issue? The Case or something like the Dip stick tube as mentioned before. Super clean and look.
     
  3. Patstuff28

    Patstuff28 Veteran Member

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    The turbo 350 in my Camaro leaks about half a quart of fluid after sitting in storage all winter. After changing the transmission pan gasket very carefully 3 years in a row I have determined that it is not leaking from there. Here are a few good suggestions on how to cure it that I will try again this spring.
    https://www.jalopyjournal.com/forum/threads/th350-leaks.1112081/
     
  4. camaro71/holland

    camaro71/holland Veteran Member

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    Just to give you an idea: I did this case this morning (A727/Torqueflite). See the high spots cought by the file. It wasn't leaking BTW.

    20210204_112753.jpg 20210204_112742.jpg
     
  5. brooksman9

    brooksman9 Veteran Member

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  6. Postmech

    Postmech Member

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    I would look at manual shaft seal, cable seal, wire pass through, or anything close to pan surface to make sure it's not fooling you. If all else fails, they make dye that shows up under UV light that pours into your fluid. Its great to find stubborn leaks.
     
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  7. Dichard

    Dichard Veteran Member

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    I have had the same issue with several TH350’s Coadster32 is right on!! The dipstick uses an O-ring in most cases and NO ONE a checks that poo. So save yourself a lot of despair and change that Sum Beach <— the O-ring that is, and if you don’t have a replacement, clean the tube up really good and put some black RTV on it, let it dry overnight. PRESTO F&*(king chango it ain’t gonna leak no more... sounds like a song of some sorts.. ya get my drift ???
     
  8. eagz28

    eagz28 Member

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    Hi
    I work at a Subaru dealer we don't use gaskets on trans pans anymore. We use pink rtv which if done right never leaks, there are several brands that make trans sealing rtv which work good but
    as mentioned the right stuff is great. hard to clean but worth it!
     
  9. ChevyReb

    ChevyReb Veteran Member Lifetime Gold Member

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    I am chasing a similar issue and already replaced the shift shaft seal once and after a couple weeks it started leaking again, like a drop in a few days, but a leak none the less, and I hate leaks! So I pulled the pan to check to see if PO put in a shift kit on rebuild and when I could see better the shift shaft had some gouges near the seal area so I bought a new shaft and put it in last night. Hopefully that will solve the issue. I had a gasket that was black and has mfg name all over one side and I got the same one to go back with. One trans guy said to tap the holes down to make sure they are flat on the pan before re-installing.

    BTW: I would probably not use RTV until everything else was known to be not leaking.
     
  10. Zzzgott

    Zzzgott New Member

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    Make sure that the vent tube is clear so the tranny is not pressurized and triple check to find the source of the leakage. The speedo's tend to seep ever so slightly. I found that my leak was from the shifter. I took the bracket off and put on a "O" ring or two for a interference fit and it fixed the problem. The rubber gasket should work fine without any sealant.
     
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