Help with 4 speed speedo drive

Discussion in 'Transmission & Driveline Topics' started by hoppin5478, Jan 7, 2017.

  1. hoppin5478

    hoppin5478 Veteran Member Lifetime Gold Member

    228
    14
    Jul 20, 2015
    Tucson, AZ
    I'm having trouble getting my drive gears for the speedo to engage on my factory 4 speed in my 78 Z28. I've replace the input gear (20 tooth), checked the teeth on the inside of the tranny and made sure that the gear in the tranny is turning appropriately. The whole where the input gear goes in the tail shaft has some wear where the gear rides and I'm wondering if something is missing or maybe my problem starts there? I have an electronic sensor in place of the cable and it is working perfectly from the input gear to the cluster, it really seems like an issue with the gears meshing. Everything worked the first couple of miles after getting the car on the road but then it died and every once in a while will catch.It seems pretty simple but I cant figure out what's going on. I'm really trying to avoid the work of dropping the tail shaft if it's a simple fix. Here is a picture of what the inside looks like.

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  2. FlaJunkie

    FlaJunkie Veteran Member Lifetime Gold Member

    5,403
    3
    Mar 24, 2001
    Indialantic, Florida
    This is what my 70 looked like...

    [​IMG]
     
  3. hoppin5478

    hoppin5478 Veteran Member Lifetime Gold Member

    228
    14
    Jul 20, 2015
    Tucson, AZ
    I figured out the problem, I should have realized it in the pictures. I wound up pulling the tail shaft housing because I couldn't really see what was going on. The internal gear has some wear but wasn't in terrible shape it turns out that there should be a machined pin on the inside of the housing that the external gear rides on to keep it centered. In the picture you can kinda tell it's all chewed up. Not only was the external gear pulling away form the internal gear because it didn't have anything to support it in the housing, the external gear was binding on the inside of the tail shaft where all the damage is. I think I might be able to center and drill a new pin that I pound in the housing otherwise it's $240 for a Richmond replacement.
     
    twozs likes this.

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