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speedo goes nuts

Discussion in 'The Garage' started by sr19, Nov 21, 2005.

  1. sr19

    sr19 Newbie

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    any one ever had there speedo just go nuts?
    like your doing 25mph and it is on 0 then 70mph
    its on 88 1500 chevy 350 tbi
     
  2. sr19

    sr19 Newbie

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    just started it and the oil gauge said 0 then i turned it off then back on and it worked fine.
    this damn thing is pissing me off!!
     
  3. sandawgk5

    sandawgk5 3/4 ton status

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    If it is the electronic speedo it might be a bad ground. The oil press gauge makes me think it maybe a ground issue. My speedo is all mechanical it can only move if the cable is turning.

    Ira
     
  4. sr19

    sr19 Newbie

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    its mechanical
     
  5. sandawgk5

    sandawgk5 3/4 ton status

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    Sounds like maybe your cable is binding up and then releasing causing the errant reading or the cable is broken and catches every once in a while.

    Ira
     
  6. sr19

    sr19 Newbie

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    i'll check it out and let you know
     
  7. pvfjr

    pvfjr 1/2 ton status

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    Pull the ratio adapter off of the t-case. It is coupled to the speedo gear with a pin that is square on one end and keyed on the other. They like to get rounded off on the square end, seen it a bunch of times. Worth checking.
     
  8. chasone64

    chasone64 Registered Member

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    Also can be the cable coming out of the adapter. Mine twisted off the cable.
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    BOUNCING speedometer will be a bad cable.

    If your speedometer just reads constantly high (or low) at times, it's more than likely the speedometer itself. It can't read any higher than you are actually moving since it is cable driven. (without the cable binding and coming loose which will cause bouncing, not long periods of high or low reading)
     
  10. opfor2

    opfor2 1/2 ton status

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    Hi there,

    I had the same problem on my 90 Blazer with a stock electronic speedo. It turned out that a wire was grounding out to the body in the eng. compartment. Fixed that and all is well. It would help to have a factory service manual with the electrical diagrams to trace the wires that go to the speedo. Hope this helps

    Dan..
     

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