I don't know anything about brushes - but it's not a lack of lubrication
type sound. It's just a loud motor type sound. As far as testing goes -
sure I made sure it ran on all speeds but you don't really notice the
sound, or at least I wan't paying close attention to that at the time.

Thanks,

Jeff
'85 GL (Gertie)
'78 Bus (Melissa) Patty's Bus