Originally Posted by phattyduck

The engine and transmission use the same harness. It runs from the boot on the firewall you see, over the engine to the driver's side, then down and back to the transmission, over the top to the transfer case and rear O2 sensor. To remove the engine and engine harness, you have to unplug everything on the transmission and it will come out with the engine. You also are supposed to remove the harness from inside the cab (ECU plugs and a few plugs to the dash harness) to have that side come out with the engine.

On a MT truck, it will only have the reverse light switch, transfer case switches and rear O2 sensor wires. The AT also need a few speed sensor signals, the neutral safety / range switch and the solenoid wires.

-Charlie