govenor ? 1990 Loyale 2WD SW

OK....I R&R'd the govenor's driven gear. And I felt inside the hole that the shaft fit in and the driving gear didn't feel concaved like the driven gear was. I'm going to take the cover back off in couple of days and check the driven gear once again to give me an idea if the gear will last any length of time. I also got another replacement gear to try and outrun "Murphy's Law."

The govenor cover has a shim washer which I assume in part determines the end play of the govenor since nothing else actually holds it in place. The only other varying factor will be the sealing gasket between the cover and the tranny housing. My question is this. How is the tolerance determined since the cover is bolted down and you can't get to anything from that point? It just strikes ma as courious and food for thought.