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Differences in Transmissions and Primary Drives

  • 03 Jun 2022 5:59 PM
    Message # 12805203

    Hi,

    I have two primary drives and two transmissions and I have noticed that there are many differences between them.

    One transmission and primary is very likely a set of matched parts from the factory. I will call it »Set 1«. The other transmission and primary is a mix of parts that came from at least 3 different motorcycles (I bought transmission, inner primary cover came and outer primary cover from 3 different sellers). This one will be called »Set 2«.

    If I start with primary drive covers.

    I have noticed that oil level plugs are not placed the same. On the »Set 1« cover it is placed lower than on the cover from »Set 2«:

    7th PHOTO

    The drive gear from »Set 1«  does not have four holes while the drive gear from »Set 2« has four additional holes:

    4th PHOTO

    The mainshaft from »Set 1« is drilled on the clutch end while the mainshaft from »Set 2« is not drilled:

    2nd PHOTO

    Notice that the mainshaft from »Set 1« started cracking from the corner of the Woodruff key slot:

    1st PHOTO

    The transmission case from »Set 1« is different than the transmission case from »Set 2«:

    3rd, 5th and 6th PHOTO

    The »Set 1« also came with an aluminum alloy generator drive, not cast iron.


    Does anyone have an idea when and why these changes were introduced?

    Which version is better?


    Cheers,

    Luka


    7 files
    Last modified: 03 Jun 2022 6:05 PM | Luka Šparovec
  • 04 Jun 2022 6:17 AM
    Reply # 12805581 on 12805203

    Indian factory tried changing the oil flow into the clutch pack in order to reduce gear grinding. My guess is that was late 26 - early 27 in the early stages of developing the 45ci engine.

    The meaning was that the clutch gear by its spinning motion should scoop up oil and transport that via a channel in the middle case that continues with the curved channel in the sealing area, seen in the one of Lukas picture of the gearbox. The motion was meant to overfill the gearbox so the excess oil would flow through the drilled hole in the mainshaft into the center of the clutch pack, and the oil centrifugal force by the spinning clutch would help separate the friction discs.

    It did not work as intended, it did not solve gear grinding. The later version, your "set 2", the Indian factory reversed back to undrilled mainshaft and the 2 large holes for eqalising oil level in the primary and gearbox. I guess that revision came late 27 or early 28, as the early version, your "set 1", is quite rare.

    Clutch covers with different height of the oil level hole can be found but I don't know when changes where implemented. I would guess without knowing that the clutch cover with the level screw higher up, really is for the  "set 1" gearbox. 

    A revision of the clutch pack was released in Augusti -28, so the factory did work continously to improve clutch release and slip.

    Earlier short frame scout gearboxes can be found with either one or 2 oil level equalising holes. For all I know they or the Chief did never have drilled mainshafts so this "set 1" was a short lived Scout experiment from the factory.

    2 files
    Last modified: 04 Jun 2022 7:06 AM | Carl-Erik Renquist
  • 12 Jun 2022 4:34 PM
    Reply # 12814158 on 12805203

    Thank you for your extensive reply Carl-Erik.

    I will make casting patterns for the transmission and the primary drive and I have a dilemma which version to choose.

    I prefer the transmission case and the clutch cover from "set 2".


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