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1989 GMC TopKick "Drop Box"

Discussion in 'Medium-duty Truck Forum' started by theIHman, Sep 30, 2013.

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  1. theIHman

    theIHman New Member

    Hi, I've got a problem. Can anyone tell me who might have manufactured a "drop box" for a 1989 GMC C7500 TopKick. This truck was manufactured in late 1988 as a cab and chassis and I have called around to GM dealers and pretty much gotten laughed at for asking about something before 1990. This "drop box" is after the Allison automatic and resembles a transfercase without the output shaft to the front and uses an air driven shifter to switch ranges. This is a farm spreader truck for broadcasting Lime/Fertilizers and all of the ID tags are rusted away and lost. If there was ever an tag with option numbers for this truck I can not find them. Any information would be appreciated about what this gear box could be would be great.

    Thanks
  2. zuki82

    zuki82 New Member 100 Posts

    I do recall, back in the day, one could get another "tranny" if you would, that was a half gear reduction! And you could get one for a half gear increase too.If not, then it might be the gearbox to run the spreader box! A PTO ya might say! Put the truck in first and drive it, and engage it, see what it does!
  3. TBigLug

    TBigLug New Member

    Do a Google search for "brownie box" or "spicer auxilliary trans". They usually came in 3 or 4 speeds and no one makes them anymore. Been doing alot of asking questions about these lately. Do some big truck junkyard hopping and check in the 60's to 80's heavier MDT's.

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