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bolt on overdrive

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Sparky, Feb 5, 2001.

  1. Sparky

    Sparky 1/2 ton status

    Aug 20, 2000
    Likes Received:
    San Antonio(summer) Texas A and M (school year)
    has anybody heard of or have a bolt on overdrive unit? I have seen them in magazines that fit 4x4 trucks. They turn your 3 speed into a 6 speed. Does anyone know how reliable or strong they are? I was thinking 5 or 6:1 gears with one of those. I would still have good driveability, and off roading would be much imporved. Let me know if you know anything abou them. The only one I have seen is about 2 grand :(


    When all else fails... Check the blinker fluid.
    78 K-5
  2. dyeager535

    dyeager535 1 ton status Premium Member

    Dec 13, 2000
    Likes Received:
    Roy WA
    Sparky, theres another post floating around out there, where I described my dads Gear Vendors unit. In my conclusion, for that kind of money, spend it on a well built 700R4. Better OD ratio, and better 1st.
    I guess GV has different OD units for different trannies, but on my dads SM465, you can NOT use it under 25mph. So it is WORTHLESS off road. You have to manually turn it on and off, if you forget to (manual tranny only I guess) you will have a hellacious downshift, which i assume after a few of those "forgot it was in OD" moments, it will tear it apart. It is basically a very small automatic transmission...it has a planetary, and a pump, which is why it doesn't work under 25mph.
    The OD ratio is something like .75, which is not much of an improvement...in 2nd gear, you still turn too many RPM's for things like towing up steep grades, etc.
    You will have to have the driveshaft shortened, and it will not work in 4WD either....the kit was extremely complete, down to the correct ratio speedo gear matched to your tires, but even the speedo cable may have to be changed, due to the length change.

    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
  3. HarryH3

    HarryH3 1 ton status Author

    May 31, 2000
    Likes Received:
    Georgetown, TX
    If you want the best of both worlds, check out the Doubler kit from Off Road Design. It's a cheaper solution to what you're trying to acheive. You can run decent gears for the street, then use double-low for off-road excursions.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>

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