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I have posted this before - we ran MTH Diesels on the 2-rail portion of the San Diego MRR Museum.  I suppose my postings drift into the past.

We got three years out of the worm gears.  That's the proper name for the bronze axle gear.  Every third worm gear replacement required a new worm as well.  MTH was very nice about supplying replacement gears.  One unit needed axle bearings after about 15 years of continuous daily museum running, and they turned out to be Piper Cub aileron bushings, cut to length.

To remove an MTH worm ( again, proper nomenclature) I have two steel bars, machined almost exactly like gunrunner's puller.  They get bolted solidly, the motor is suspended from them in a steel tube with a cushion in the bottom to catch the motor.

Then the worm is heated with a torch - hot, but not discolored, and definitely not red.  The motor shaft is tapped with a tiny drift pin and a hammer; the motor drops onto the cushion, and a new worm is inserted with shaft Loctite.  Never damaged a motor.  In fact, those motors were indestructible - I don't remember replacing any.

I had to move a pinion on a new lionel replacement motor. The bottom of pinion had to sit in bearing in bottom of truck. Had to move about .160.I tried old slot car puller nope. So I made one basically a 'fork'. Used two 3/8 plates with 5/16 fine thread bolts. Made fork just big enough for pinion to fit. Wish I had a milling machine,used drill press and grinder. I used finishing nails,all I had,for inside pinion,bent them, about 6 finally got it moved. I practiced on old mth motor. Seems old motor pinion moved way easier than new motor. Heating and cooling cycles!?? I need to get a harden shaft to really work better than nails.

I use the Great Planes Gear Puller, it's pretty robust, but it didn't survive the cut, and I bent the pin.  Still trying to get a replacement pin, hopefully from stronger material.


Break the cage on a roller bearing and use the rollers.  They are very hard and will not bend.

I made a plate similar to that bottom plate but I couldn't harden it and it ended up bending.

Dave, I'd have to find roller bearings that have a step in them as the pin does in the foreground.  I think that's unlikely to be easy to find.

John, I bought one of those and played around with it to see what the best possible scenario might be.  I took your stepped pin and turned it around and pressed against a pin from a roller bearing.  The gear came right off.  I don’t know how it even worked for you the other way.  The step is too large on the OD and not long enough.  

The press is towards the bottom 1/8” of the gear.  This will allow you to insert a pin that is too big.  The pin always gets stuck at the end.

I did taper the end of my pin by inserting it in a drill and honing it down at the end. (I know you don’t have machine tools)

Anyway, I hope this helps you and the OP.  This is a nice little puller!



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Last edited by David Minarik


The bearing was an INA for a Harley transmission countershaft in the case.


The pin punches might be a great source!  Thanks for the tip.


I will send you one

You just gave me a thought, ......Borg Warner & Tremec T5 transmissions are loaded with similar needle bearings,..and they’re in plastic cages, so really easy to harvest,....AND I have boat loads of them since I rebuild them on a weekly basis,...I’ll check it out tomorrow while I’m at work,....I might have a lifetime supply for all of us,....thanks David!..


@JET posted:

"We got three years out of the worm gears.  That's the proper name for the bronze axle gear. "

The worm gear is always attached to the motor or driving shaft. The driven gear or axle gear is called the "worm wheel."

Respectfully, worm gear and worm wheel are synonyms.

The "worm" or "worm screw" is on the motor shaft.

I would say for for the majority of our trains lubing the gearbox is fairly easy. MTH and Williams diesels require a single screw removal to drop a truck. newer Lionel diesels with Liondrive just require a 90 degree twist of the truck. Most steam engines have a screw to remove to allow greasing the gearbox. Just a matter of keeping track either by run time or years to do this maintenance. It helps if the manufacturers use the best materials and design in the first place.


I’ve been following this thread with interest. Not because I have any plans to remove a worm gear from a motor shaft but, more as a reminder to myself that work like this is way beyond my skill set.

Thank God there are people like Pat, Dave and GRJ (to name a few) who really know what they are doing!

I’m also thankful for my own anal retentive side that convinced me years ago to maintain a maintenance log on all of my locomotives and see they are serviced at least every 2-3 years based on run time. Hopefully that “ounce of prevention” keeps my engines out of the shop for the “pound of cure” represented by new motors with original worm gears.


Last edited by juniata guy

Since I asked the question and started this post and am very gratefull for all the responces that have been posted, it is a wealth of  information

Anyways I thought I would  share that I bought I  think 6 motors that were taken out of  MTH trains and they all have worn gears on them and another 4 that are still installed in diesel frames, that have the motors and the trucks  attached but no boards, so if anyone is in dire need of a motor with a worm gear already on it , let me know and I'll see if I can't help you out.


Well, I see a lot of them, especially the tinplate O and Std Gauge stuff, and the brass "worm gear" is all chewed up and dry.  You'd have to disassemble those every 20-25 hours and grease the gear to keep it lubricated, I suspect very few people actually do that.

Well i suspect if you tried marine grease which is very sticky and tacky and will stay in contact with the mess gears, maybe that would last much longer, i know it is a excellent wheel bearing grease ! IMHO


Last edited by Alan Mancus

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