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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.

Thanks,

Don

12-26-21 update:  Gear just slips right off - trying to locate motor assembly with tach tape and reader installed

Last edited by DGJONES
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@GGG posted:

Boy that is a new one.  Never saw that before.  If you can pull off by hand I don't think loctite would be a permanent fix.  I would look to see if the worm is actually cracked.  You could order a new motor.  G

We have seen that at MTH.  Quite rare, but the symptom is the flywheel spinning with the gear slipping on the shaft.  The worm has a stepped hole, so only the part near the motor is fixed to the shaft.

Thanks to all who replied!  The worm just slips right off and there are no signs that he shaft was ever staked.

I was just able to find the MTH product number  (30-2805-1) so that I could order the motor.  Unfortunately, the MTH parts side says mechanical parts "List coming soon".

I suspect the motor is used many other models so I was wondering if anyone knew the correct part number for motor with tack and sensor installed,

I appreciate the help,

Don

Shaft Loctite is the cure, if the worm is not split.  I fixed a pulley on a small table saw that way 40 years ago, and it is still holding.  We do driver tires, and even loose driver axles with shaft Loctite.

The proper nomenclature - the thing on the motor shaft is the "worm" and the gear on the axle is the "worm gear."

I have a pair of brand new MTH SD trucks with motors - but I am going to sell them as a pair.

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