Hi Derril,
Here’s a simple solution you might try as a last resort. Disconnect the power pickup wires from each truck (hopefully they have the little red jst connectors) and connect them to the battery car plugs on each end. Be careful about the polarity!!! Now, simply slide the switch to battery, and you’ll have track power. Switch to track power and you’ll have no power.
It may be really easy if the leads are long enough from the trucks to reach the end plugs. The red male jst plug can actually connect with the female battery car plug.
Take off the body, might just have the track pickups un-plugged.
Found the problem. Looks like someone at the factory unloaded their grease gun in both of the gearboxes. The copper contacts were completely covered and could not make contact with the wheels. After a thorough cleaning ad re-assemble they run great!