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'78 K5 Speedo Adjustment Gear??

Discussion in 'The Garage' started by AZOffroad, Feb 19, 2006.

  1. AZOffroad

    AZOffroad Registered Member

    Jan 9, 2006
    Likes Received:
    Gilbert, Arizona
    With 35" tires on the K5, my speedo does not reflect the correct speed. As was the case with my CJ-7, I expected to just have to swap out a $15 gear and it would be a done deal. The local speedo shop is telling me it requires something else (I think the called it a "ratio adapter"???) and it's fairly expensive (like $160).

    My setup is 100% stock other than a 4" lift and 35" tires.

    Are these guys full of it, or is it really that expensive to make my speedo read accurately again?


    Gilbert, Arizona
    1978 K5 400ci/TH350/NP203 Daily Driver
  2. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

    Dec 14, 2001
    Likes Received:
    Pleasanton, CA.
    When i've done a gear swap or tire size change i just took my truck to the speedo shop and about $100.00 later i drive out reading accurately. There is an adapter box made by stewart warner i believe that does get costly if it is needed for the correction. If that is the case go to your local wrecking yard and look at some tranny's and pull one off, just make sure that it is a bolt together type and not riveted. There are 4 gears inside the reduction box and the speedo shop must be able to take the 2 halves apart and swap gears to make your speedo correct.

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