There's a lot of good info about this here:
https://bobsobol.smugmug.com/T...PD-Drive-Train-Work/
I have shamelessly copied everything I learned there and from several threads on here with MaxSouthOz and others and it works great with the Finescale 360 chassis and drive upgrades. I recently added a Maxon coreless motor, Loksound Select HO decoder and Tang Band speaker to the upgrades on an RC GP9. My best running and sounding loco so far!