Repair FM Tranmaster Truck Gear

You may want to look into the gear well now to figure out if you need to fab a standoff to set between the frame and new gear, to keep the gear straight and level while pressing the new gear onto the axle.

Yes I thought ahead and made a spacer I can use. I have one for the gear and actually two for the wheels. I just have to wait for the gear to come in to see if everything will work.

I made wheel jig for a drill press vise that should hold everything in alignment. In my head and in theory it should work for the FM truck.

I have not taken the gear out yet as it looks like it goes in just one way. This way I will not forget the direction it goes.

It takes an arbor press for MTH.  Perhaps that is why your axle gear slips.  If you are sure it is plastic, then you need a knurled axle.

The bronze gears in MTH and K-Line are truly a tight press fit.  Ours never slip.

  Nylon and plastic gears splitting radially from the axle hub outward is pretty common among mfgs. 

The splitting also happens on postwar here's 2331 that I had to replace one gear. When putting on new gear add a drop of oil to prevent splitting of new gear.

You might want to try heating the gear. This will cause it to expand and make it easier to slide onto the axle.

Maybe a good thing I bought two gears. Hopefully I can get it together with out an arbor press. Not a big deal as it is on my list to buy someday. I like to try what I have and if it can't be made to work then I buy the proper tool. First time for repairing gears so if any one has tips I'm greatful for them.

You can use a large c-clamp since your working on one axle at a time. I make shims by cutting a slot in washers to clear axle you only need a few. Good Luck! 

I thought a picture would be helpful. I have taken that axle out of the truck. Pretty straight forward after pulling a wheel. I have included the wheel puller so you could see what I used. Also you can see how the gear split.

I thought a picture would be helpful. I have taken that axle out of the truck. Pretty straight forward after pulling a wheel. I have included the wheel puller so you could see what I used. Also you can see how the gear split.

The problem gear. You can see the split. No issues with the teeth. No issues on the motor worm gear either. 

My gear came in today. If your interest the part number is 623-22. It was really a very simple straight forward replacement. It took less than 10 mins to replace and then put everything together.

I used my drill press vise and it worked just great. While pressing the gear and wheel on at the same time I used the tip of a small flat head screw driver to keep the gear centered on the axle. The axle has a spot for the gear to set, so it is easy to get the right setting. You have to make sure to align the outside gear while pressing everything together.

I just took my time slowly pressinghile working the gears to get them to set correctly.

The wheels were centered and 100 balanced. The motor work gear matched up perfect to the new when gear.

I gave it a half hour workout and all is fine.

So my total cost was $16.94. I bought two gears at $6 each then had to pay a little postage.

Just trust me if you can change oil in your car you can replace this gear.

Next up fixing my horn in my Lionel F3 New York Central, just waiting for parts.

Sorry thought I added photos

Wow-Even though an older post this is exactly what has happened to my Southern FM with both of its nylon gears---must be a common problem with these type of gears. For short term I was lucky as I had two older FM trucks I had purchased and just put them on and all was fine.  I decided to try the above (replacing the gear myself)---I used a nail punch and tapped the axle to free the plain wheel off enabling the gear side to be removed....then trying to think how the heck do I get the new brass gear centered properly...I too thought about using a shim etc...but I chickened out! Fortunately a friend nearby who once had a Lionel service station and all the proper equipment was called upon by me to complete the job....so I  left both trucks and new brass center gears with him to finish the job after the holidays. I loved reading this post and only wish I had stumbled across it before because I would have tried completing the job. Steady and slow and patience. Glad it all worked out for you--thanks for posting this info.

Eureka!  Just got a call this morning and already picked up both pair of trucks professionally repaired.  Kudos to George Small who operates a Lionel repair center and has an unbelievable service work area with all the tools and parts anyone can imagine.  Thank you George and honestly I am glad I did leave the repair to the pro with knowhow. However it was interesting that original post and mine were the same Southern FM engine----with those center nylon gears in the trucks. Now that I have the brass gears I imagine all of us even if you have to pay a little extra for originally when purchasing a unit with brass gears would gladly pay instead of having the frustration of those nylon gears splitting.  This was great link to the repair to keep in mind if and when needed.  Thanks again to everyone responding.