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Technical TH350 Pan gasket with stamped steel pan.

Discussion in 'Traditional Hot Rods' started by roju1985, Jun 28, 2019.

  1. roju1985
    Joined: Apr 22, 2019
    Posts: 5


    Hello all,

    Forgive my stupidity I'm still learning about these things. I have a new turbo 350 that I had to pull the pan on because the speedometer clip broke and went missing, but that' s another story. Basically I'm ready to put the pan back on but I want to do everything in my power to keep leaks at bay.

    I have a stamped steel pan with the raised bumps on the sealing surface. The transmission came with a rubberized cork gasket but I got fluid on it when I dropped the pan so I'm not sure if it should be replaced or if I can just clean it with simple green and apply a thin layer of permatex anaerobic gasket maker just for good measure? If I have to replace the gasket what type should I use. I sourced a felpro neoprene gasket because I couldn't find rubberized cork locally, but it's thinner than the cork gasket so I'm unsure if it's meant to be used with a steel pan or not.

    I'm likely really overthinking this but I really don't want to do the job twice. Thanks everyone for your input!
  2. alanp561
    Joined: Oct 1, 2017
    Posts: 1,022


    Wipe it off with a dry cloth . Use Permatex #2 non hardening sealant. Done

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  3. squirrel
    Joined: Sep 23, 2004
    Posts: 45,821


    no sealer is needed on transmission pan gaskets....

    Look carefully at the pan surface, are the bolt holes pushed "up" some? if so, tap them down with a hammer, while the edge of the pan is laying on the edge of a work bench.

    Clean everything well.

    Look a the gasket, is it compressed at all, damaged in any way? If not, then you might be able to reuse it. But it would be good to get a new gasket. The non-cork paper type will work, if the pan surface is flat, everything is clean, and you get the bolts to the correct tightness. But the rubber gaskets are kind of iffy.
    rockable, Jibs and bundybiker like this.
  4. tomcat11
    Joined: Mar 31, 2010
    Posts: 128

    from Kalifornia

    I would use a new non cork paper type gasket. Spray the pan rail and the pan side of the gasket with fast tack. Leave the tranny side clean and dry. This helps keep it in place and the holes lined up. Permatex 2 works too as do other sealers. I would not use RTV silicone. Don't over torque the bolts.
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  5. I recomend what tomcat11 said but i threw away my original steel pan and went to a aluminum pan with a drain hole. Best choice ever. I had to file the pan surface flat before i put it on.
  6. squirrel
    Joined: Sep 23, 2004
    Posts: 45,821


    most pan gaskets these days have four bolt holes a bit smaller than the rest, you can put the gasket on the pan, put those four bolts in (they will thread into the gasket) to hold the gasket in place, and install the pan. No need for fast tack or anything.
    rockable and saltflats like this.
  7. saltflats
    Joined: Aug 14, 2007
    Posts: 9,996

    from Missouri

    I like to use the Farpak/ Duraprene pan gasket if I can get one.
  8. I am not fan of the rubber gaskets. But if that is what you got that is what you will use.

    I cannot see the cork gasket that you removed but they commonly get oil on them when you pull the pan. I normally wipe it down with solvent and glue it to the pan.
  9. The temptation to over-tighten the pan bolts probably causes as many leaks as anything else. If you've got an inch-pound torque wrench, use it. If you don't, then use only a short handled 1/4" drive ratchet with a short extension. Put the extension between your middle and ring fingers to cut down on the amount of leverage you can apply. Walk around the bolts and snug them up a bit at a time. You'll get a feel for when they're "snug" enough without mashing your new gasket.

    Works good for valve cover gaskets too. ;)
    saltflats likes this.
  10. Barn Hunter
    Joined: Feb 15, 2012
    Posts: 1,327

    Barn Hunter

    I've got a turbo 350 with a chrome pan and have a leak even though we were pretty careful tightening the bolts. I've been told that it's better to go with an aluminum pan. The trans is aluminum and the two should expand/contract at closer to the same amount as compared to the different metals, aluminum/chrome.
  11. 427 sleeper
    Joined: Mar 8, 2017
    Posts: 957

    427 sleeper

    Use a gasket that comes packaged flat!!! The gasket's that come wadded up in a kit will ALWAYS leak. Make sure the pan rails are flat, and use ABSOLUTELY NO type of sealant! Sealant's cause more problems than good. Don't over tighten. Snug is just good enough. JMHO.
    Joined: Jul 20, 2006
    Posts: 2,402


    In all my years doing transmissions professionally I never used a sealer of any kind. Make sure that the bolt holes are not pushed up in the pan. Tap them down with a hammer use a good cork gasket and you won’t have any problems
    rockable likes this.

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