ALSO.....unfortunately, most of these geartrains will have components that are slightly Out of Round.
What that means is that The Spur gear mesh COULD be Perfect in one spot but too Loose/Tight in another. You gotta check it ALL the way around, and the adjustment will probably be a compromise.

This is Especially true with Transmissions where you replaced only the SPUR gear, because the other Gears AND the bearing seats in the Housing will be slightly worn too.