Euro truck bearings and a metal pinion (same tooth count as stock) allowed. motor heat shield can be removed. only battery is the peak 4200, can change batter plug to Dean's, ECS or traxxas.
the spec motors for TC are reedy. We started the 21.5 class with a hobbywing motor but they became too hard to get a hold of. Not 100% sure if they are required to be purchased at the track or not. Tire is open for now.