Ok, my SP SW1500 has a weird running issue, the rear truck does not engage correctly between the tower gear and the worm gear. I swapped the trucks, same issue, regardless of which truck is in the rear. It pulls better than it pushes, both directions. I know that this is not normal, my daughter's BN SW1500 runs great, pulling 15 MTL cars with ease. Mine can't push 3.
Is there any flash or deformity around the truck mount on the frame itself? I'd say if nothing jumps out at you for what could be in the way, maybe try contacting MTL's customer support, see if they can offer an idea or assist.
You have to be very careful in taking it apart. This MTL locomotive is very delicate. I have two SW 1500's. One has sound with a ESU Micro Sound decoder and the second is straight DCC. Shades
