Something is not making sense to me. The OP states these are horizontal motors. Lionel made F3s with this motor from 1948 through 1954. They switched to vertical motors in the F3s with the 1955 production. AFAIK, all the gears made during this time for the F3s were metal. There were no nylon, or other plastic gears. Nylon or plastic gears did not appear in Lionel production until the MPC era. And when MPC reintroduced the F3 in the 1970s, they went with the vertical motor, not the horitontal motor. Again, AFAIK, no horizontal motored F3s were produced after 1955. So MPC and follow-on entities would have no reason to make the idler gear, period. So it follows that the nylon gear in question is not original to the motor assembly. And it is not made by Lionel. So someone in the after-maket parts industry made it, as there is a need for this particular gear. I would be very curious what the hole for the stud looks like (is it worn or egg shaped?), whether the idler meshes well with both the drive gear and the truck gear, and how the gear compares with one from a low mileage 1949-1954 unit.
Chris
LVHR
