The Bachmann two truck Shay (late model) was locking up .The timing gear for the drive unit had part number G811x-OZFO4 (the small quarter moon looking piece) missing. My fix was to remove the tiny retainer screw and insert a .040 dia by about 1/2'long brass wire through the screw hole. Put a tiny drop of CA glue on the point where the brass wire passes through the inverted question mark piece. Then cut the wire snug with a pair of wire cutters.
I did this for all 6 units. The replacement repair does not show to the viewer when the steam engine is reassembled into the Shay!
I did this for all 6 units. The replacement repair does not show to the viewer when the steam engine is reassembled into the Shay!