Attached are pics of my 616 ATSF Switcher motor frame.
It was running poorly so I started to rebuild it. I discovered that the amrature was popping up & down 2~3 mil when reversing. After dismantling the truck I found that the drive gear (600-111) had an egg-shaped bearing surface in the aluminum motor truck frame. The entire unit was still packed with greasy/oily schmutz that was not all caked/dried and was still reducing friction. I also quickly noted the ball-bearing (600-110) and thrust washer (600-129) were AWOL. I think the missing items are probably the biggest contributory factor for this worn out power truck. Those tiny little items always seem to fly out when servicing motor and if you didn't think they were important, well...