Of course I am. If I wasn't obsessed with exercises in futility, I wouldn't get any exercise at all. I've got it apart right now for a diff rebuild. Did find a lot of carpet fluff jammed in the back of the gearbox, but nothing that would make a noise. With the motor removed, the drivetrain was more sluggish than when I built it. Played around with loosening screws, no real change. I'll just put it back together (carefully) tomorrow. I still don't have the motivation to sleeve anything.

Interesting point about the new version of the motor plate. I'd noticed before that there was a 1.5mm recess cut into the motor side. What I didn't notice was the 1.6mm shaved off of the spur gear boss, thus necessitating the 1.6mm spacer behind the spur gear. Interesting, but why?