Results 1 to 7 of 7

Thread: Gearbox Countershaft Shim?

Discussions of Triumph motor cars

  1. #1
    Senior Member
    Join Date
    Feb 2018
    Location
    Central Mississippi
    Posts
    70
    Thanks Thanks Given 
    4
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Gearbox Countershaft Shim?

    I read in the Green County Triumph gearbox rebuild guide that you can place a shim next to the distance piece to decrease countershaft end float so that it's between 6-10 mils (7-12 mils in the later manual). Is this really acceptable? It just seems like a 3-mil shim would wear over time and break away, potentially causing damage to the gearbox components. FYI my end float currently sits at 12-mils (out-of-spec for my manual), and I am trying to decide whether to shim or not. Thrust washers are in spec, so I think the wear occurred on the distance piece - assuming the end float wasn't borderline from the factory.

    Countershaft Shim.JPG

    Joel

  2. #2
    Great Pumpkin TR3driver's Avatar
    Join Date
    Aug 2003
    Location
    Sunny So California
    Posts
    18,989
    Thanks Thanks Given 
    4
    Thanks Thanks Received 
    72
    Thanked in
    69 Posts

    Re: Gearbox Countershaft Shim?

    All those gears turn as one, so the shim won't see any motion.

    As noted in the article, you can add a shim between the thrust washer and case, if you prefer.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

  3. #3
    Yoda CJD's Avatar
    Join Date
    Feb 2011
    Location
    Southlake, TX, USA
    Posts
    5,087
    Thanks Thanks Given 
    4
    Thanks Thanks Received 
    19
    Thanked in
    19 Posts

    Re: Gearbox Countershaft Shim?

    I agree. Where you have the shim will make inserting the countershaft into the case much easier. Trying to place a shim and thrust washer in alignment while you also align the shaft will be infinitely more "fiddly" than shimming the spacer in the gear stack.
    John

    1955 TR2

  4. #4
    Senior Member
    Join Date
    Feb 2018
    Location
    Central Mississippi
    Posts
    70
    Thanks Thanks Given 
    4
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Re: Gearbox Countershaft Shim?

    After mocking up the countershaft assembly, I noticed that I can spin the distance piece around the shaft independent of the gears. I assumed that this occurs to some degree during operation as the oil is expelled through the two holes. That was the root of my concern. The manual also says to replace the distance piece or thrust washers to get up to the proper end float, so I thought there might be some reason why they don't instruct to shim. I'm beginning to think my gearbox came from the factory "out of spec" since both washers measure center of new condition. Thanks for the advice.

    Joel

  5. #5
    Yoda CJD's Avatar
    Join Date
    Feb 2011
    Location
    Southlake, TX, USA
    Posts
    5,087
    Thanks Thanks Given 
    4
    Thanks Thanks Received 
    19
    Thanked in
    19 Posts

    Re: Gearbox Countershaft Shim?

    In gears 1-3, with the gears being helically cut, they place an end load on the gear stack on the countershaft. During that time there will be no movement of the distance sleeve in relation to the gears. In 4th gear the gears are relatively unloaded on the countershaft, but the input gear helix is still spinning the stack in thick oil, and there is still a slight end load on the end piece. Although in 4th the distance piece CAN move... it both has no force acting on it to cause it to spin, and it has no loading if it does to cause wear. If wear was an issue, then the factory would have pinned the distance piece.

    Remember that the manual was written when the factories were still making these gearboxes, and parts were very easy to find. They don’t, and they aren’t anymore. Shimming the distance piece is simply a suggestion. If you can find an oversize piece, then use it.
    Last edited by CJD; 03-28-2018 at 12:25 AM.
    John

    1955 TR2

  6. #6
    Senior Member
    Join Date
    Feb 2018
    Location
    Central Mississippi
    Posts
    70
    Thanks Thanks Given 
    4
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Re: Gearbox Countershaft Shim?

    Great information John. Never thought I'd learn this much about manual transmissions, much less rebuild one. I think I will shim.

    Joel

  7. #7
    Great Pumpkin TR3driver's Avatar
    Join Date
    Aug 2003
    Location
    Sunny So California
    Posts
    18,989
    Thanks Thanks Given 
    4
    Thanks Thanks Received 
    72
    Thanked in
    69 Posts

    Re: Gearbox Countershaft Shim?

    Quote Originally Posted by Joel M View Post
    I'm beginning to think my gearbox came from the factory "out of spec" since both washers measure center of new condition. Thanks for the advice.
    Very possible, IMO. Or, it might be that the case has become slightly distorted somehow. I've even seen them damaged in that area by a thrust washer failure.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •