The locomotive wheelsets with gears run from $6 to $7. Trying to pull off a wheel, force on a plastic gear without breaking it, and then replacing the removed wheel with the precise gauging of the original seemed to be far more effort than just buying the entire wheel/gear set. Replacing the set is a very simple matter but does take some patience because the bearings rotate around the axles and, like frisky 2-year-old kids, refuse to go where they're told. I broke off the defective plastic gear on the bad axle and saved it for future projects.
I have bought American Models parts for detailing, upgrading, and repairing my own mistakes over 30 years. They have always had the parts available; and I suspect that for drive-train parts such as wheels, wipers, motors, and gears they keep an ample stock. These parts are common to multiple AM locomotives, which makes parts management simpler and keeps costs down.
