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Thread: Super turbine 400? behind my 401 nailhead

  1. #1

    Super turbine 400? behind my 401 nailhead

    I have a rebuilt ST 400 trans I'm planning on using in a 30 Model "A" coupe. I'm building an old school rod with Buick power Could someone clue me in on the "variable pitch" feature on this tranny and how it works?. Is there some kind of linkage from the carb to the tranny? (like a kick down) What would be a good way to apply or modify this feature for some weekend dragstrip action behind a 401? I was told a ST 300 torque convertor mated to the ST400 gives more stall and would be the setup in this light weight car. Anyone have experiance or speed secrets with this combo? Thanks in advance!

  2. #2
    The variable pitch feature is controlled electronically by a solenoid in the transmission. When 12V is applied, the vanes in the torque converter shift angles giving it a different stall speed. On the OEM equipped cars the converter went into high stall on two ocassions: First - when the car was at a complete stop; this avoided creeping and was controlled by a switch on the brake pedal. Second - when the driver got heavy with the right foot and put the car into passing gear. The gears shifted as the converter went into high stall.

    You're correct; the use of the ST300 converter behind the 401/425 will give it an even higher stall.

    There are two terminals on the outside of the transmission, one for the kickdown, and one for the torque converter. All GM TH400's have electric kickdowns; you can borrow from one of them, use the OEM piece that came with the car (requires carb, linkage, and brackets from the same year), or there are aftermarket pieces available from Jegs and Summit.

    I tried attaching an illustration of how to put a toggle switch into the OEM setup, but the file is too big. Give me your email address and I'll send it to you directly.

    Ed

  3. #3
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    Read my post under engine and Transmission swaps.
    Would switch to a 300 torque converter solve my problem mounting trans to engine?

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