TH400 leaking

Discussion in 'The "Juice Box"' started by Thomas Patrick, Mar 14, 2020.

  1. Installed a 455 with a th400 in a 1969 skylark last summer, everything was great. Over the winter storage I noticed a leak near speedo cable. Fixed it. Now just started the motor for this season. Placed trans fluid in the dipstick, did not over fill. Shortly after while the motor was running I reved the motor and trans fluid came shooting out of the dipstick. Few days later I started the motor, added trans fluid. Now the fluid no longer comes out of the trans dip stick. Now it appears the trans fluid is leaking on top of the lower part of the headers, on passenger side. When I rev the motor more fluid comes out on to the lower part of the headers. Not sure where the trans fluid is coming from now. Any idea what is going on?

  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I'm not clear on what "on top of the lower part of the headers" is. Look at the cooler lines coming out of the transmission.
  3. Bens99gtp

    Bens99gtp Well-Known Member

    The only things there are the cooler lines, vent tube, and dipstick tube.
  4. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    I had that happen with a clogged vent. The mud wasps filled it for me when the car was sitting. You'll have to get underneath and see where it is coming from. There's no other way to do it.
  5. flh73

    flh73 Well-Known Member

    The trans leaked from speedo while stored because the converter on 400’s drain back into trans filling the tail of trans. I had a one that after stored would weep from the output yoke small hole in the center onto the u joint. I second the vent is plugged.
  6. Golden Oldie 65

    Golden Oldie 65 Well-Known Member

    I fought with one last year on a `68 GTO. In the end I found that the O-ring was leaking around the plastic housing that the kickdown wire plugs into on the left side of the trans. It was dripping down and following around the pan rail making it difficult to pin exactly where it was coming from.
  7. 1969RIVI

    1969RIVI Well-Known Member

    ^^^This right here is one of the leaks I had before I did the rebuild.

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