TH350 issue 81 square body pickup

Discussion in 'Transmission & Driveline Topics' started by JWZ28, Nov 14, 2015.

  1. JWZ28

    JWZ28 Veteran Member

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    Ok fellas, buddy of mine has an 81 square body with a 350, cam isn't stock but not radical. The previous transmission was burnt up by a previous owner. We swapped another th350 (stock convertor) into the truck from an 85 square body he has. The trans worked fine before the swap. He changed the filter and refilled with fluid. Vac line is hooked up to full manifold on the carb. Fluid is full.

    Now for the issue. When he puts the truck in gear it pulls load off the engine as it should, but he has to very lightly feather the gas to get the truck to barely move. He says when he gives it normal throttle it stops moving and revs as if in neutral. He's rechecked fluid multiple times and its full. I know near to nothing about automatic trans so any help would be much appreciated.
     
  2. Gary S

    Gary S Administrator Lifetime Gold Member

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    Like you, I know nothing about automatics. As far as I know, there should be no real differences between the 81 and 85 transmissions, so incompatibility should not be an issue.
    However, I have seen automatics fail to work after being drained and refilled with new fluid more than once. Pulling and installing the tranny could have done something to it that it it didn't like.
    Hopefully, some expert here will give you a real answer.
     
  3. 81BirdMan

    81BirdMan Veteran Member

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  4. JWZ28

    JWZ28 Veteran Member

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    The torque converter is bolted up. I actually checked that myself. I told him not to change the fluid since we didn't know if it had ever been changed. I had heard nightmares about people changing the fluid and draining all the friction material out with it rendering the trans useless...... He did it anyway. The fluid that came out of it didn't look black or anything, but who knows....
     

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