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Thread: 45 Flathead Tranny Issue

  1. #1

    45 Flathead Tranny Issue

    Just a recap, my transmission on my flatty was bucking in second gear. First and third were fine, just second. I finally found the time to pull it and check it out. All the gears look great, oil as well. I found one of the shifter forks bent, could this have been the reason why second gear was missing and if so why did it bend? I'm going to tear the tranny down anyway, just was wondering if anyone had any input
    "The impossible missions are the only ones which succeed.” ~ Jacques Cousteau


    Al C

    1942 WLA Civy Custom
    1928 JDL Special Sport Solo (Basket)

  2. #2

    Re: 45 Flathead Tranny Issue

    I recall that there was an error in the reprint manuals for the shift fork spacing dimensions.I could be wrong as the memory banks are not what they used to be.I'm sure someone will chime in.

  3. Re: 45 Flathead Tranny Issue

    Alan, when I rebuilt my transmission last winter, I also had bent and chewed up shifter forks. For my money that is an end result of a different problem, not the actual problem. Also when adjusting the second gear to second gear retaining bracket clearance check to make sure everything is true and flat. My retaining bracket had a bevel in it giving me all sorts of issues. Again, an end result of a sloppy transmission. After that got replaced I found out the second gear I had was chewed up where it rides on the spacer. This would give me different clearances as I spun the gear. Literally it would go from in tolerance to rubbing then back to tolerance. The gear looked fine to the eye, had to put it under a magnifying glass to see all of the pitting. That also wound up being replaced with a NOS gear which then gave me a consistent clearance.

    Hopefully Paps will chime in as I know you and I both followed his thread religiously during our rebuilds. Good luck.
    1946 WL Solo
    1970 FLH
    1991 Sportster XLH
    1997 Wide Glide FXDWG
    2005 Road Glide FLTRI

  4. #4

    Re: 45 Flathead Tranny Issue

    Every messed up 45" trans I've seen in recent years had this problem.When setup properly the shift clutch does not have pressure on it when in gear.The shift fork should be loose in the shift clutch in each gear..as I've said before always shift into each gear and you should be able to "rattle" the shift fork.Even if I had no books thats the way to check them.The problem with 45" trans is second gear dogs are inset in the gear not protuding like BT.To center the gear in neutral the face of second gear is pretty close to aligning with the edge of the shift clutch.Usually it will destroy the shaft,shift clutch,second gear,and the shift fork.

  5. #5

    Re: 45 Flathead Tranny Issue

    The problem with second gear is the second gear retaining bracket. None of them set square in the case when mounted. False readings are acquired using feeler gauges in the wrong spot on the retainer bracket. The key to a good clearance setting there is feel all over and take the tight setting as the right setting.

  6. #6

    Re: 45 Flathead Tranny Issue

    I'm tearing it down this week coming up, there is no visible damage besides the bent shifter fork. I'll keep everyone updated. Thanks for the tips
    "The impossible missions are the only ones which succeed.” ~ Jacques Cousteau


    Al C

    1942 WLA Civy Custom
    1928 JDL Special Sport Solo (Basket)

  7. #7

    Re: 45 Flathead Tranny Issue

    After inspection, without removing the shifter drum, I noticed the shifter fork shaft was protruding from its recess behind the drive sprocket. I removed the drum and found the shaft had worked itself out.



    Last edited by alanc48; 11-25-2015 at 09:35 AM.
    "The impossible missions are the only ones which succeed.” ~ Jacques Cousteau


    Al C

    1942 WLA Civy Custom
    1928 JDL Special Sport Solo (Basket)

  8. #8

    Re: 45 Flathead Tranny Issue

    Al...check your sprocket cover gasket surface. There is a dowel pressed into it which retains the shaft. That dowel will be in line with the end of the shaft.

  9. #9

    Re: 45 Flathead Tranny Issue

    After pulling the forks and shaft I found that the fork on the clutch side was grabbing on the shaft, a high spot. I recon what happened is while I was shifting the fork grabbed the shaft and pulled it out of its seat, taking the whole assembly out of wack. The only damage is a bent fork and both have wear on the faces. This would explain how the transmission was fine for so many miles and all of a sudden had bucking in second.

    "The impossible missions are the only ones which succeed.” ~ Jacques Cousteau


    Al C

    1942 WLA Civy Custom
    1928 JDL Special Sport Solo (Basket)

  10. #10

    Re: 45 Flathead Tranny Issue

    Quote Originally Posted by chibobber View Post
    I recall that there was an error in the reprint manuals for the shift fork spacing dimensions.I could be wrong as the memory banks are not what they used to be.I'm sure someone will chime in.
    This is true. Many service manuals have the clearances reversed but the specs are correct.

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