Transmission TH400 fluid leak- Help

Discussion in 'The "Juice Box"' started by Ryanjbill15, May 14, 2018.

  1. Ryanjbill15

    Ryanjbill15 Well-Known Member

    Hey guys- I picked up a 72 skylark with a 71 455 stage 1 + TH400 trans. All rebuilt but it seems there is a leak coming from the trans. It's not coming from the tail shaft and only leaks after I have ran the car and it sits for a few hours or longer. I ran it yesterday checked it and it seems to leak a small pool of tranny fluid but only after the engine and tranny were ice cold (I.E. sitting for multiple hours).

    Any idea what this could be? It doesn't leak that I can tell while running.

  2. TexasT

    TexasT Texas, where are you from

    Dipstick tube if it is in the front area. There is a "top hat" rubber seal that can get pinched when inserted. If not there, where does the leak appear to be coming from(front, rear, which side)?
  3. Ryanjbill15

    Ryanjbill15 Well-Known Member

    I took a closer look and it appears to be coming from the front right. It could be the dipstick or it could be the right corner of the pan. maybe once the converter drains back it fills up and leaks?
  4. Daves69

    Daves69 Too many cars too work on

    Could be from the vacuum modulator.
    john.schaefer77 likes this.
  5. Ryanjbill15

    Ryanjbill15 Well-Known Member

    Thanks guys. I am swapping out the gasket today since that was leaking in a few areas as well. Figured I'll get one and see if that does it.
  6. Ryanjbill15

    Ryanjbill15 Well-Known Member

    Update- New gasket stopped 99% of the leak which is great. but it looks like there was a small amount of fluid on the flywheel cover this morning. My guess is its the front shaft seal and the pump seal. Its small enough right now that I don't know if I want to bother pulling the whole tranny to do that....Maybe just monitor. What do you guys think?

    BRUCE ROE Well-Known Member

    I fix major leaks. Can't stay ahead of the minor ones, so I have a big
    drip pan under the car. Bruce Roe

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