Premier SD70ACe trucks sparking

There are wires that run down inside the 3/2 trucks that should have plastic insulator around each wire. This wire goes to the power pick-ups. I found one once, that this insulator was missing from the factory. When the truck would go into turns and the wire got flexed, it would short out.

I don't see it here

http://mthtrains.com/sites/def...loded/20dl13009e.pdf

maybe that's only important on 2 rail versions?

For sure rear trucks only?..tested with lights out in your room? The reason i mention this is i have had bad 2/3 rail switch. I removed the switch and wired direct.

Check coupler wires, motor wires, tighten ground screw and no nick on red center rail wire especially under insulation near truck.  Also the 2 rail pickup wires mentioned.  Some where there is a damaged wire.  G

Also check ditch light wires if equipped. One of my Dash 8's had a ditch light wire smashed by the frame causing the side frames to spark and short out the engine in curves. 

Great ideas will check these out I appreciate it guys

Here is a pic of the suspect truck. The brown wire in the center is loose, as the black rubber grommet that is held in place apparently is no longer correctly working. Could this be my issue? The end of the wire that goes inside the truck block appears to be on a spring and is very loose. Thanks and how do I fix this?

One end is a ring tongue(should be tight and not hitting the truck) and the other to a small spring loaded plunger for 2 rail operation held down by the insulating plate.I believe it is be out of circuit when 2/3 rail switch in 3 rail. Compare all of this to your healthy truck if you get brave.