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Chief Overdrive Gearbox - Sprung Frame or Rigid - Whats the difference in gearbox?

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  • Chief Overdrive Gearbox - Sprung Frame or Rigid - Whats the difference in gearbox?

    A little history. Bought my 1940 Chief maybe 10 years ago, it had the 3 speed gearbox. The bike was partially apart when I got it so I decided it was going to be a complete restoration, which it was and it went really really well. I never got to ride the 3 speed as I purchased a 4 speed which was "suppose" to be for the sprung frame, which my bike is. I finished the restoration a few years ago and have been ridding the bike working out little bugs, as you can tell from some previous threads. I fix or correct things as I go and continue to ride the bike, which is an amazing machine I I love how it responds and runs and rides. Ok so heres the thing!

    When I assembled this bike I found I had to place a 1/4" washer on the rear axle to get the drive chain to align properly. (move away from the wheel),. Nowhere could I find reference to this washer and I remember researching all the other components to see if something was off or aftermarket, etc. The bike rides just beautiful and the chain is happy (I think) and really its just something in the back of my head that knows its probably not right and I need to address this, especially since the exhaust is coming off next week so I can address some other things.

    I added the 4 speed, perhaps the seller was mistaken and it is really for a rigid frame? How do I tell? (are they longer shafts or shorter?). Ive asked Stark if they have records of the serial numbers but he does not, I have reviewed all my documentation to see if the main shafts have any dimensions that I can measure but I cant find this information anywhere. (I am assuming the only real difference is in the main shafts length?). I know its a big ask, but I am wondering if anyone has one of these gearboxes accesable at this time and its possible, could I get some measurements, its does not matter which one as I will measure mine next week and then hopefully can figure out if mine is correct for my bike or not? Any ideas or information on these gearboxes would be useful as the technical info is around but missing some very key details.

    Any other thoughts related to this need for a washer are welcome, perhaps its not the gearbox after all?

    washer1.jpgwasher2.jpg
    Attached Files
    Last edited by NiteOwl; 07-17-2021, 03:51 PM.
    Bob Beatty
    AMCA 19209

  • #2
    NiteOwl

    Is your four speed an Indian crash-box or one of the new/modern synchromesh "Byford" four speeds?
    I believe the Byford's are for 1932-1953 Chiefs.

    Checking Jerry Geers
    Transmission mainshaft (for 3sp crashbox) 11.188 inches. Might help to look at diagram there as Geer's provides some other measurements.

    Geer's also shows Byford 4 spd fitment appropriate for 1940 Chief.
    Last edited by PaulCDF; 07-17-2021, 05:39 PM.

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    • #3
      Mine is the new style made in Bellingham, now being taken over by Stark. I know they are still gathering parts. I'll look closer at greers sight but I could not find the info before. Especially a sure fire way to look at the 2 gearboxes and know which is which. I assume it's the length of the shift and there must be a measurement a person could take in situ with the chain cover off? . . . Hmm yes I should be able to measure mine and compare to the appropriate 3 speed for mainshaft as long as the castings are real similar. Thanks! Will check it out. Was out ridding again today, these bikes are so nice to ride.
      Last edited by NiteOwl; 07-17-2021, 06:44 PM.
      Bob Beatty
      AMCA 19209

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      • #4
        Good idea; compare distance between transmission case and final drive sprocket current transmission and 3 speed.
        While on Geers maybe check out WHEEL ASSEMBLY Rear HUB. Perhaps over time something was added lost, worn or not up to spec to mis-align drive chain?

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        • #5
          Plunger frame drive sprocket is 1/4” or so out from the rigid with longer mainshaft ,sprocket driver gear and spacer
          take our washers and you are likely off that much which would mean rigid trans

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          • #6
            Thank you, I will hopefully be diving into this tomorrow.
            Bob Beatty
            AMCA 19209

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