Can anyone tell me how to remove the front truck of a Bachmann Heisler. I have a binding somewhere. The motor drives the front axel properly (with the side rods removed) but the back axel which drives the shaft underneath to the valve gear only allows that shaft to turn about one revolution before a hard stop. I would like to remove the front truck completely to separate it from the shaft underneath and valve gear to isolate the problem further. Not sure what screws to tackle.