i know it is an old retired set but I bought one from a friend and built it ...(no missing parts) after I built it everything looked good and never had a problem linking anything but no moving parts worked,, but I could hear the motors working...i figured i missed a gear or didn't push axle in all the way or something so I tore it down and now rebuilding it and tested it when i put the motors on...something i did not do the first time...and I don't think it is doing right the red gears is not turning nor is the axle i tried to upload a video but it was to big