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

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

  1. slayer021175666

    slayer021175666 Veteran Member

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    I've mentioned before that my tranny pan leaks. Seems I've tried everything to no avail. I had the stock pan on it and it leaked. Tried cork. Tried rubber. Nothing gained. Still leaked. I thought I'd throw some money at it and get serious so, I bought an aluminum pan and a $35 gasket from Moroso. Big thick blue one with rubber molded around a steel core. No Dice! Leaking worse than ever! I've heard of sanding the gasket surface of chrome pans. Would that work on the aluminum pan? I just don't know what to do. I'm thinking about omitting the gasket and gluing the pan on with grey RTV. What a shame to do it that way, though. I'm sure it would stop the leak but, It'd be a MAJOR PITA when I need to pull the pan off later. I've never had so many fits in my life getting one to seal. Hoping you guys have some guru knowledge for me. I'm also open to a miracle, potions, chants, dances and anything else short of, selling my soul. I'm still using it, right now.
     
  2. Zspoiler

    Zspoiler Veteran Member

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    Make sure the surfaces aren`t warped first .The thick FeLpro gaskets with blue "RTV " mostly works as well.
     
  3. camaro71/holland

    camaro71/holland Veteran Member

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    When you've tried several different pans with no luck, then the problem might be the case flange itself. Try to straighten the flange with a long (fine tooth) file. The case needs to be empty of course and cleaned thoroughly afterwards.
     
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  4. Chevyforever

    Chevyforever Veteran Member

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    Is there any chance you have too much fluid in trans ?
     
  5. Coadster32

    Coadster32 Veteran Member Lifetime Gold Member

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    I had a same issue going back a few years now with a TH400 tranny pan. I tired Moroso gasket, cork, rubber, rtv...and the darn thing kept leaking. I sealed up the speedo gear housing, and the vacuum modulator as well. Come to find out, there was a crack in the dipstick tube that was seeping the fluid.
     
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  6. John Wright

    John Wright Veteran Member Lifetime Gold Member

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    It's hard to believe that didn't seal, those will seal on a warped or rough surface. Can you clean everything really good with brake kleen or carb cleaner, get it really dry, then start dusting it with flour and see if you can find where it is seeping out before it turns into a drip and runs...
     
  7. COPO

    COPO Veteran Member Lifetime Gold Member

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    I would smear a small layer of RTV on both side of the gasket.
     
  8. budro6968

    budro6968 Veteran Member

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    I would check the case flange with a straight edge. Make sure it is flat. Has the trans ever been in a wrecked car? Could have a hairline crack.
     
  9. sandlapper

    sandlapper Veteran Member

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    how about checking the new Cast pan's rails on a surface plate or pane of glass; may be new Casting but warped as well. If so; pounding on it's rails (like a stamping) ain't gonna help.
     
  10. GoldenOne7710

    GoldenOne7710 Equal Opportunity Offender Lifetime Gold Member

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    Might look for other issues than the pan gasket leaking, too. Leak could be coming from somewhere else. What area of the pan is wet?
     
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