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My 1989 F350 4wd Crew cab has a M5OD. My original harness had to be replaced. I had no other option but to go with a 1990 harness as it was mostly plug and play. I'm thinking it was off an E40D application. I have a couple of wires I can't figure out.
In the first image I'm guessing the two on the left, based on the wiring, are for the E40D. What is the black connector next to the green connector from my original chassis harness? It's a 3 to 1 connector.
In the second photo, what is this black plug on the new harness near the wipers?
There is no way of knowing unless you carefully call out the wire colors in the connector. That is not as easy as you would think, the colors fade and some of them have faint stripes on them. You do not have your old harness laying around?
I did a c6 to zf swap in my 89, it originally had the c6. I had a donor and it was plug and play. In your new E4OD harness coming down to the trans there should be a red with lightbue stripe wires. The original ZF harness that I plugged into mine accepted these red/lightblue stripe wires, and all it did was jump them together. The two red/lightblue stripe wires are for the starting circuit. The automatic has a neutral safety switch, the zf has this located on the clutch pedal. So if you do not get this resolved, the first thing you will notice, it will not crank with the key.
I believe there was another sensor going back to the transfer case for the 4x4 light.
Call out what the wire colors are in the connectors you have a question about, and we might be able to figure it out from the diagrams.
Franklin2 thanks for the response and help! Referring to the top picture, the original going in was actually two wires - red/white stripe (maybe originally pink with a white stripe) and dark green/purple stripe. The dark green/purple stripe comes out and back along the frame. I haven't followed it yet.
I can't find the wire color matches in either my EVTS Manual for the 89...nor in Chilton's. The engine cranks as it was originally M5OD tranny. Maybe you're right about the backup light...I'm looking into that now.
The red/white may be a wire that goes to the electric shift module. If this truck had, or the truck where the harness came from had a electric shift transfer case, it would have used this wire to let it shift to low range. The more complicated switch on the automatic would have grounded this wire when it was in the neutral position. You never know, all trucks may have had part of this wire hanging there, even though they did not have electric shift.
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