Hello everyone I'm new to the site. I have come across many threads on the site that refer to my exact problem. Which is the e40d trans. There never seems to be a final post of how the problem was finally fixed. My problem with my e40d trans is that there is no voltage to the red wire on the passenger side of the transmission. Yet I have power to the yellow wire on the drivers side, as well as power to the yellow wire to the computer. I"ve had a shudder in overdrive ever since I bought it, 1993 E350 7.3 diesel, Ambulance. So one morning I get in start it up and go to take off and it would not go into first on its own [ had to do it manually to shift thru all 3 gears to get it to move]. I got out of the truck to check the trans fluid and it was fine. At the same time I noticed the box marker lights were on, with the switch off, truck running. When I pulled on the light switch the box markers went out and the headlights came on. Everything had worked flawlessly since I bought it. I saw a post that LEDs might have something to do with it. I thought they were joking. I had replaced the marker lights six months ago with LEDs. I fortunately ran into a guy at a party tonight that owned a trans shop. He verified that this was a possibility, They had a fire truck in with all kinds of electrical Poltergeists. He said one of his smart guys figured it out the night before. He came in and changed the rear lights and that fixed the problem. The guy I met, knew a lot of the trans guys that I knew, and have used over the years. I had even had a few done at his dad's old shop. [small world] Any how, I had the trans rebuilt, with all heavy duty stuff, and a billet torque converter, put it in and had the same problem. I"ve pulled the computer out which I didn't know it had. [been a turbo 400 guy myself for a lot of years] I"ve checked the continuity on the harness from the trans to the main harness every wire checked out with 12 volts. I even took it out completely to visually check it and rewrap it. [no rub throughs anywhere, great condition.] Next ,I intend to pass voltage through main harness to the fuse box in the engine compartment. Now I have 3 books from the library to help me figure out where these wires go.
Any help would be greatly appreciated !!!

 

When there is no power to the red wires the problem is often a bad relay that supplies power to the computer.

 

relays are good. do you know which slot under the relay supplies the power, so I check for continuity.

 

No, I do not.

 

Found a excellent schematic on the eec relay, from wayback. diode is good,(bummer). going to check the sockets . Then get a scanner like you have posted on so many other threads.