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Old October 22nd, 2023, 05:41 PM
jgpnashville jgpnashville is offline
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Truck: 1967 K15 305E
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Default 67 K15 Wiring Questions

I have owned my truck since early this year when I bought it from my employer. It runs and drives well, thanks to several tips from board members.
I have two questions:
1. Being a 1967, it has a reverse gear backup light, which in my truck relies on a switch on top of the SM420 transmission that engages when the shifter moves down and to the left, into reverse. My question is what color wire should connect to this reverse switch and should that wire some from underneath the truck (up and around the tranny) or should it come from inside the cab and run under the floor mats and the shifter boot? My truck is missing that wire altogether and I would like to reinstall it so the back-up lights work. The lights themselves are fine, but I’ve pulled the fuse since they are on all the time. I guess whatever circuitry was added to the 67s to do the reverse light on the SM420 defaults to lights on when the switch is unplugged. Any tips on replacing this wire? I cannot tell where said wire would go, either, so whatever guidance on that would be helpful.
2. Radio Speakers - my truck had the radio delete panel, but the panel fell off its little clips that are inserted into the left & right knob holes. The clips are still stuck in the holes, but they have come detached (unsoldered) from the radio delete plate. Seeing this, I was going to install a radio and am curious where others have added speakers to their trucks? I know the dashboard is an option, but what about 6x9 speakers in boxes, either behind the seat (I have a gas tank there) or under the dashboard, down by the kick panel vents? I’ve seen pictures of people with speakers in a box in front of the floor shifter, but since I have a transfer case shifter, there’s not much room there for speakers. Curious what others have done.


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Old October 22nd, 2023, 07:06 PM
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Funky61 Funky61 is offline
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Default Re: 67 K15 Wiring Questions

Here's what I found for question One;

This has a schematic



The dark green wire is the power feed that runs from the fuse box to the switch. Then the light green wire goes from the switch back to the lights.

With the 4-speed trans, those dark & light green wires both run through the engine harness bulkhead connector on the firewall. That takes them outside the cab and to a 2-terminal plug that connects to the switch on the trans. Inside the cab, the light green wire just runs a short ways from the engine harness bulkhead connector over to the rear light harness connector and from there runs to the back of the truck.
1961 GMC Suburban 305A Overdrive
1962 GMC Utility 305D
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