@Dieseler and @ADCX Rob, my reference to nylon is one of guesswork. I suppose it could be made of some sort of plastic or even Delrin. I absolutely cannot attest to the age of these motors and trucks since that's how I got them, as just motors and trucks, 4 separate items. And this is really only the second time I have repaired a horizontal drive motor, the first being an early 2020 as I recall. 
The pic above shows what I'm dealing with, I believe it is a 2343-196 gear and a 2343-187 Stud (Idler gear.) Although the gear teeth don't look too bad, the inside of the gear has a good bit of wobble on the stud mount. I have sourced the same white gear from Trainz, and the stud from both Trainz and Jeff, and a metal version of the gear through Jeff, although I forgot to ask about the thickness of his metal gear. This white gear appears to be thicker than metal gear, so I'll be asking him to take a quick measurement later.
I would be interested in learning any more identifying features of the motors, such as the use of this white gear, or even the hole used to punch the stud out of the block (both of my motors had this hole), the transition year from bronze sleeve bearings to ball bearings, the different brush plates used (mine are 2343-119), etc.
George
