Hi. I've just come upon this thread and would you believe it, I have just yesterday been given a very old Bachmann loco from my brother in law to fix with what appeared to be the same problem you're encountering. First off, it only has one power truck at one end and a free wheeling truck for power pick up at the other. The powered truck does not (in this case) pick up power. The motor sits above the truck and is what I would call from my slot car days a side winder,armature across the frame. To try and get this beast to run I first did a circuit test and found that the black wire onto the pickup truck was broken, fixed that,cleaned the wheels, lubed it and got it going and what a noise. Tracked it down to a lot of use in the past and not too much future to look forward to. I don't presume you can buy gears or parts for it so I'll just park it back at his place.Cheers Rob.