The Stovebolt Site Forums The Shop Area The Electrical Bay Overdrive Wiring Harness from Jim Carter - Updated with Results

This might not be the right place, but if anyone knows these harnesses, it's you guys. SWEET, feel free to move this if you like.

Getting ready to rework the electrical side of things for my trans rebuild (at this thread: https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=987859#Post987859).

Considered building my own harness, but also looked at what I'd spend in wire and terminals. Checked eBay and found that the harness for my truck are around $95.

Then saw that there was one for the same year range from Jim Carter for around $26. Here: http://www.oldchevytrucks.com/cart/index.asp?sdes=overdrive

Why the big difference? Hard to tell from the picture if all the connectors are standard or not and the descriptions for these things are atrocious.

Anyone used the Jim Carter harness on their OD?

Thanks,

Jim

I make my own up using an original wiring loom as a sample. I can't make one for what those guys are getting for them. There are some differences between the connectors on the factory relay from 55/56 to 57 up but everything else should be the same. The early ones use ring connectors and the later ones use spade connectors.
The ebay guys are probably buying them from old trucks for $25 and selling them for $95.
Fred

The year is 1957...very few interstates (if any) or divided highways with easy and safe opportunities to pass. Ours was a nation of two lane blacktop with - - - - - or_________, to pass Dad tromped on the go faster pedal and she'd kick down from OD to the 'passing gear'. I have my OD on a switch conveniently located on the dash so that I have all the usefulness of the kick down without it's limitations. A Bosch relay, some wire, I doubt if I have $10 in materials. The most important move I made is using the governor, I didn't in my 'old od' so that I could split the gears and get 6 forward gears, with the governor and my '69 od I have 5 forward gears.

Cosmo

If you have all the factory components that harness would probably work. I used a Bosch relay and a DPDT toggle switch and wire mine like this.

Thanks guys,

I think I'll give the harness a try. I have all of the other components that were original; the kickdown switch with what appear to be the proper connections (though it looks to have some non-standard nuts on it), an original-looking clear rubber piece that used to hold the kickdown connection to the wiring harness, plus the crusty remnants of my wiring that I tried to clean up and patch but just don't trust.

I also have the original governor switch that I tested using Fred's procedure, an original relay that I still need to test, and now a solid OD transmission.

Will report back any surprises on the harness.

Appreciate your inputs.

Jim

The Jim Carter harness arrived and I must say I was impressed. The wires are heavily insulated, have connectors on them that match the application, and everything is protected within some woven plastic (vinyl?) sheath that looks great.

One of the two modifications I had to make was to cut off the four butt connectors that run to the kickdown switch and replace them with female bullet connectors that fit the posts of the kickdown switch.

You can see that everything is labeled well. When I test-fit the harness in the engine compartment, I found that every wire length was perfect for the length and path of the connections. Using my shop manual and the RPO 315 pages, I tried to install everything as it was from the factory. During the test-fit, I found these dimples in the firewall; two of which lines up with the holes in my original relay. I drilled them for metal screws and they were a perfect fit.

Here's how the main harness and relay setup looked on the firewall during initial installation. May do something with the brown power wire that runs to the non-resisted side of the ballast resistor to clean things up, but the harness fit perfectly.

Here's the cluster of four wires I added the bullet connectors to and how they fit the kickdown switch. Note that the length is perfect. Someone put thought into this.

I fabricated the bracket that the kickdown sits on from a diagram provided to me by rfs56trk and a couple of pictures of an original bracket from eBay. The tab that rides the throttle rod uses a cable clamp to hold it in position. Pretty neat homemade rig.

Here's the portion of the harness that travels down the transmission tunnel/firewall area down to the transmission. Perfect length. And this is the solenoid section installed. My truck always had this padded loop on the upper right transmission side cover bolt that I never understood what it was for. Now I know. Keeps the harness secure and away from the moving parts. And again, the length of the wires fit perfectly my overdrive solenoid setup. This was the other modification I had to make; The terminal loop was just a hair small for the #4 terminal post on the solenoid, so I cut a kerf in it and widened it out to the correct size. Took ten seconds.

So the verdict? I got a $26 wiring harness that would have cost me more in parts to fabricate. It installed perfectly to the factory locations specified by Chevy in my manual. It was sturdy and well-insulated. And it was $70 cheaper than the exact same type harness on the other sites.

The two modifications I had to make were probably required so that the harness could fit with what consumers have encountered in their builds. My mods required minimal tools and mere seconds to make. Only other note is that the wiring diagram, being that of the original Chevy one, was a bit sparse. However, it was labeled to help us novices and, once I got over my initial worries and started to test-fit the thing, the diagram made perfect sense.

Well done, Jim Carter. More business coming your way.

Jim

Something is wrong in your schematic Cletis. 85 and 86 terminals are switching terminals and should be opposite each other. power will flow from 30 to 87 terminal or the reverse 87-30 depending on how you want it wired. Not trying to find fault, but for correctness sake. Your wiring diagram is awesome.

Thanks for the info. I didn't realize there is a standard way for relay schematics. I don't do this for a living. I hope no one has been confused by it.