Question out of couriosity

OK...Got the Subie govenor fixed. At least temporarily. It killed the driven gear to the govenor. Feeling inside the input shaft hole the drive still felt intact. I got two more driven gears (one to fix it the other to try and beat Murphy's Law)and replaced the worn one. Works fine now. I'm going to put a couple hundred miles on it and check for undue wear again. That way I can at least keep track of how much life may be left.

But ANYWAY in doing this operation I noticed the govenor's end play is dictated by by the cap over the govenor. There is a shim washer in this cap and the only other thing that would determine the clearence is the gasket between the cap and the tranny body. Now. My question is how do you determine the proper tolerence between the cap and the govenor top when the cap is bolted down over the govenor? I'm just courious about it.