1. #1
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    Default Allison Transmission Gurus, please lend your expertise

    My Volunteer Rescue Squad is looking at a used Rescue truck.

    It's a 1993 GMC Topkick chassis
    12,000 lb front
    23,000 lb rear with 4.11:1 R&P
    Caterpillar 3116, 220 HP rating
    Allison MT643D transmission.

    Here's my questions:
    How can I tell if the PTO is engine or turbine driven?
    The owner's manual says it can be either.

    If its turbine driven, how can I tell if the torque converter has lockup ability?
    The owner's manual says it can be either.

    We need this info to determine the feasibility of retrofitting a PTO generator at a later date.

    If the PTO is engine driven, lockup ability of the torque converter won't matter. If the PTO is turbine driven, and it doesn't have lockup, then we're limited to no more than about 12kW of generator power.

    Already faced this once before with a Allison AT545 years ago.
    The American people will never knowingly adopt Socialism. But under the name of 'liberalism' they will adopt every fragment of the Socialist program, until one day America will be a Socialist nation, without knowing how it happened. --Norman Mattoon Thomas, 6 time presidential candidate for the Socialist Party of America

  2. #2
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    Default

    Quote Originally Posted by txgp17 View Post
    My Volunteer Rescue Squad is looking at a used Rescue truck.

    It's a 1993 GMC Topkick chassis
    12,000 lb front
    23,000 lb rear with 4.11:1 R&P
    Caterpillar 3116, 220 HP rating
    Allison MT643D transmission.

    Here's my questions:
    How can I tell if the PTO is engine or turbine driven?
    The owner's manual says it can be either.

    If its turbine driven, how can I tell if the torque converter has lockup ability?
    The owner's manual says it can be either.

    We need this info to determine the feasibility of retrofitting a PTO generator at a later date.

    If the PTO is engine driven, lockup ability of the torque converter won't matter. If the PTO is turbine driven, and it doesn't have lockup, then we're limited to no more than about 12kW of generator power.

    Already faced this once before with a Allison AT545 years ago.
    I know there's an Allison dealer near you; call them with the trans serial number. They should either be albe to tell you or at least tell you what to look for on the trans that would answer the question. Stay warm!

  3. #3
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    Answer found, courtesy of Rich at Covington Power Systems.

    A MT643's PTO is turbine driven. But, he said all MT643's have lockup ability in the Torque Converter.

    To enable this, a solenoid must be added that will lock the converter up while in neutral, and it must disengage before shifting to any other range, otherwise it will bring the engine to a screeching halt.
    The American people will never knowingly adopt Socialism. But under the name of 'liberalism' they will adopt every fragment of the Socialist program, until one day America will be a Socialist nation, without knowing how it happened. --Norman Mattoon Thomas, 6 time presidential candidate for the Socialist Party of America

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