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Thread: Speedo woes

  1. #1
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    Speedo woes

    Hi All,

    74 2 door always had the speedo flickers and shut up shop about a year ago.

    Not the cable, not the right angle drive but the little white gear inside the actual unit. The following is some info from Philip A on this issue:

    'I had a problem with an 81 in Saudi that may be the same.
    If you pull the back off the speedo if it has the old type cluster, you will see a small white cross shaft that is driven by a gear under the input shaft.

    This drives the odometer and has a gear on one end and a lever on the other that pushes the ODO one 0.1Km at a time.

    This cross shaft can run dry and seize, and maybe lose a gear tooth if left too long. The increased load as it pushes the lever causes the speedo to jump or more correctly slow down.
    Regards Philip A'

    The gear is nylon on a metal shaft and splits causing terminal munching and would be the cause of the demise of many a right angle drive.

    Nylon contains some water which is lost over time causing shrinkage and brittleness, especially in the binnacle in the sun.

    I transplanted a gear from a spare speedo and all has been fine for a year but now the same thing has happened.

    I've looked on the net for replacement internal Smiths parts with no success. The whole unit is available new still ........for a kidney.

    Would an instrument maker be able help with just the gear? Any other suggestions?

    thanks, DL

  2. #2
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    Bumpity bump...

    Does anyone have a surplus speedo?

    Or, perhaps more interestingly, does anyone want to have a go at making the gear / shaft on their 3D printer?

    DL

  3. #3
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    Sorry can't help on either of the topics you've raised, but Howard Instruments could be of help

    They're located in Heidelberg.

  4. #4
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    Ha! an oldie but a goodie.
    I actually made up a new tooth for the gear using a hard plastic araldite type stuff that was available back in 1985. I reckon you could use Q bond to do the same now.
    I dobbed it onto the gear the used small files to make the new tooth.
    It worked fine for the period I had the car.
    The original problem IMHO is the drying up of the grease inside the shaft housing.
    Regards Philip A

  5. #5
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    Thanks guys.

    I'll give Howard a call if Philip's method doesn't work on the spare unit.

    A drill with one of those square screw drivers is perfect for testing.

    cheers, DL

  6. #6
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    Ok, this has taken awhile, been busy.

    Got a hold of the small Q Bond kit from Blackwoods, there were only 5 in the whole of OZ. $34

    The gear that screws up is only about 10mm in dia and maybe 4mm thick.

    I got the stuffed one out of the spare speedo, degreased it and thought no way this is going to work.

    The nylon had obviously shrunk, gear had a radial split so 2 teeth were double the normal spacing causing the jamming.

    Anyway............... Q Bond kit is pretty awesome, nearly gave up twice after having the speedo reading perfectly but not when installed.

    To cut it short, it's back in my POS and running perfectly tonight, odometer as well. There are quite a few tricks involved to get this repair to work, I did take pics and will put them up with a step by step if anyone is interested.

    If your RRC speedo needle is doing the jerky thing it's only a matter of time before the RH drive goes on permanent leave or the cable breaks. And you still have the cause to fix.

    The latter is only $25 but the former is around $300.

    A drill with the bit I previously described is NOT perfect for testing, you have to use the bit in your fingers to really sort the problems as you go.

    And thanks again to Philip A, I never would have thought this type of repair was possible.

    cheers, DL

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