I am helping a friend with a MTH PS2 Southern Trainmaster that will barely move. All the DS functions are working correctly but the locomotive will barely move. Inspection revealed that one motor was working OK but the other, while wheels would turn ok with engine upside down in cradle but if you touched the wheels, it would stop. I removed the shell and separated the motor from the trucks and discovered the worm gear was slipping on the motor shaft. In fact, you could just pull it off. Is this something that can be repaired or must I buy a new motor?
I would appreciate help on how to proceed.