mainshaft/countershaft shimming
12-01-2013, 06:50 PM
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mainshaft/countershaft shimming I just built a gto t56 using a new mainshaft and koyo bearings. While checking end play I found:
- The mainshaft had .02" of end play.
- The countershaft had .04" of end play.
For the countershaft, the shim kit I received had a lot of options so I went with .043" and now it feels tight. The smallest shim I had for the mainshaft was .023" so that's what I went with. Is a slight preload on the mainshaft ok? My measuring equipment isn't exactly ideal so I could be off +/- a few thousandths.
Also, is it normal for the countershaft extension to require no shim? I checked it while the transmission was laying horizontally and I wonder if that could cause the countershaft extension to get stuck even though it needs a shim.
- The mainshaft had .02" of end play.
- The countershaft had .04" of end play.
For the countershaft, the shim kit I received had a lot of options so I went with .043" and now it feels tight. The smallest shim I had for the mainshaft was .023" so that's what I went with. Is a slight preload on the mainshaft ok? My measuring equipment isn't exactly ideal so I could be off +/- a few thousandths.
Also, is it normal for the countershaft extension to require no shim? I checked it while the transmission was laying horizontally and I wonder if that could cause the countershaft extension to get stuck even though it needs a shim.
12-01-2013, 07:40 PM
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I went back out to the garage and checked the countershaft extension again and this time it moved. There was about .045" of end play so I stuck in a .045" shim. Maybe the race was wedged the first time? In any case, this feels a lot better.
12-02-2013, 03:36 PM
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One other thing I read was that, given you might preload the countershaft, you have to take that into account when shimming the mainshaft. I didn't do that in my measurements above so with the additional end play of ~.003" on the mainshaft, the .023" shim should be ideal.
In any case, it's back together so we'll see if my bearings explode when it goes into my road racing track car.
In any case, it's back together so we'll see if my bearings explode when it goes into my road racing track car.
Last edited by orion4096; 12-02-2013 at 09:33 PM.
12-02-2013, 04:25 PM
#4
Some of the countershaft extensions require a couple thinner shims to get an acceptable amount.
The other potential issue is easy. Don't pre-load the counter before taking mainshaft numbers.
Put the thinnest shim in each to start. Then torque the case. Then measure. You want a short amount of endplay in each in order to get a valid number. But you don't want it full loose which can lead to sloppy numbers.
The other potential issue is easy. Don't pre-load the counter before taking mainshaft numbers.
Put the thinnest shim in each to start. Then torque the case. Then measure. You want a short amount of endplay in each in order to get a valid number. But you don't want it full loose which can lead to sloppy numbers.