PDA

View Full Version : TR2/3/3A Gearbox Countershaft Shim?



Joel M
03-26-2018, 11:07 PM
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.

53015

Joel

TR3driver
03-27-2018, 12:38 AM
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.

CJD
03-27-2018, 10:21 AM
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.

Joel M
03-27-2018, 08:20 PM
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

CJD
03-27-2018, 09:09 PM
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.

Joel M
03-27-2018, 10:35 PM
Great information John. Never thought I'd learn this much about manual transmissions, much less rebuild one. I think I will shim.

Joel

TR3driver
03-27-2018, 11:06 PM
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.