I wonder is someone in the trucks past wanted to add the electric adaptor after the vacuum one attached to the back of the speedometer went bad. All you would need is a switch on the dash with 12 volt keyed power for manual use...
Chevrolet always recomended trucks be parked in Low Range...had so oldtimers tell me the 2-speed rears could drop into neutral (between gears) and free wheel if the truck got bumped while parked. Hi Range is UP on the actuator on the rear housing and gravity could pull it down. I don't know it this is true or not, but I park mine in Low just in case it is.
If I had a truck that would be in HI forever, I would somehow lock the rear shift linkage back at the rear so it couldn't move. I would hate to hit a pothole and have it fall into Low Range while I was traveling the country side...
Mike B
