Speedometer Drive Gear

Discussion in 'Troubleshooting & Diagnosis' started by tnt30143, Aug 21, 2017.

  1. tnt30143

    tnt30143 New Member

    8
    0
    Jul 15, 2015
    Jasper, Georgia
    Hello all. I tried searching but couldn't find an answer. The speedo quit working in the 1980 Z. I did the cable spin and the gauge worked, so I went to the next easiest and changed the driven gear. Got the correct color and number of teeth, put it in and it still doesn't work. Next step is drive gear. Is there any way to tell the color/number of teeth without actually pulling the tailpiece? I don't really want to pull it more than once, and my son doesn't want to not be able to drive it while it's waiting for the part. I tried the formula on the TCI site but I'm not sure my algebra came out right. It has a 22 teeth driven gear, the formula comes up between 8 and 9 teeth on the drive gear, a little closer to the 9 side. Then on one of the threads I found searching said something about a 3:1 ratio which would make the drive gear 7 teeth. Any help is appreciated.
     
  2. RS1979

    RS1979 Veteran Member Lifetime Gold Member

    2,436
    207
    Jun 18, 2013
    Memphis, TN
    Does your car have cruise control? My '79 came with it and I had the same problem your having. I removed both of the original cables and replaced them with the non-cruise control cable. Works fine now.
     
  3. tnt30143

    tnt30143 New Member

    8
    0
    Jul 15, 2015
    Jasper, Georgia
    No, no cruise control. Only "luxury" option this thing has is delay wipers.
     
  4. RS1979

    RS1979 Veteran Member Lifetime Gold Member

    2,436
    207
    Jun 18, 2013
    Memphis, TN
    In that case, you can remove the driven gear and the bullet. Then look inside the hole and see what color it is.
     
  5. tnt30143

    tnt30143 New Member

    8
    0
    Jul 15, 2015
    Jasper, Georgia
    I wasn't sure if I could actually tell anything looking through that hole. I'll try that and see if I can see anything. Thanks.
     

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