Excellent post Scott. One little trick I like to use which saves you a trip if you dont have your tach which btw is hard to run the car and hold a tach on inspection. Put two marks on the drive sheave about example 12:00 and 3:00. Using the stopwatch on your phone, while running the car via UA or DA relay, time the sheave to go from mark to mark each direction. It will be very easy to determine which direction is faster. One of the other mistakes guys don't realize is often you will only get about 1/2 a brush use. You are working with brush holders that have long lost their effective tension.