Does anybody know why the tailgate hinge has a wire that spans the pivot pin and connects the two "wings" of the hinge? Is this wire for body grounding the tailgate?
I ask as I was performing a pre-winter inspection and took a look at the two tailgate wiring harnesses. I noticed a frayed wire poking thru the joint on the driver's side hinge. The actual tailgate wiring harness is intact (All of the tailgate's electrical accessories work) but this wire is not as it is split at the pivot but remains welded to each wing.
Thanks to anybody that can let me know the purpose of the wire and how critical it is.

Yep, exactly. It grounds the tailgate electrical functions.

Yes, it is to ground the tailgate. Other than the door lock motor, the other things need to be grounded to work. (I also suspect tailgates rust quicker when not properly grounded.)

Run an extra grounding wire (or two) from the door to the body, bypassing the hinge, if you are doing a rewiring job to reposition the other wires outside the hinge.

eg. http://www.vclassics.com/archive/tailgate.htm
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1980 245 Canadian B21A with SU carb but electronic ignition and M46 trans in Brampton, Ont.

Thnaks for the response. All of the tailgate electricals work except for the power door lock and that I took to be a disconnect between the door lock actuator and the wiring harness. The passenger side tailgate hinge has a wire connecting to both hinge wings but will replace the broken wire on the driver's side hinge per your post. Thanks for the link to the VClassics Interactive as it appears to have some great how to advice.