Ted S posted:
Speaking of which, @49Lionel what kind of motor does your 19th Century loco have? I can't help but feel that maybe something is binding on yours, because as John said, the 28:1 locos are usually very smooth runners. The little RS-365 revs to 12000 RPM or more. If the worm gear isn't pressed onto the motor shaft (and unfortunately many of them are , you could probably swap the motor for another one with lower RPM and more torque.
I don't know what motor it is, but here's the best picture I have:
When I had the rods off I tested each component and didn't detect any binds. I'd definitely be interested to see how a different motor would perform, but that's not something I'd try doing myself.