Here we have a good used chassis wiring harness removed from a crew cab short box 2005 GMC 3500hd with the 6.6 Duramax and 4wd transmission. This is the harness that runs from the fusebox to the rear bumper. This is used, but removed from a running and driving truck. This will fit most crew short 04-05 trucks but please compare it to your existing harness plugs to ensure its the one you need, if you need any parts just inquire.
