Being the technical director for the valve body and solenoid department, I've seen more than my share of errors and mistakes that have been made by people while working with automatic transmissions. The majority involves electrical components, and a majority of those involve the connectors in some way. Often damage to a connector is done during the disconnection process. We've all been told not to wiggle a connector to get it off; that can expand the female pins in the connector, and cause them to have poor, or no connection when plugged back in, i.e. 604's. Also connectors can have special problems we need to watch out for, such as inserts that may come lose from the solenoid block and stay in the harness connector, like the early E4OD in (figure 1).
In the later E4OD and 4R100, Ford just reversed the problem so that now part of the harness connector may stick in the solenoid block as in (figure 2). Miss either one of these and you may not be able to connect the harness to the block, or the connector won't have a weather seal and corrosion can quickly set in and cause some serious problems.
The 42LE connector also has an issue with wires flexing and braking, you'll need to peal back the insulation to see this headache causer, (figure 3) shows you were to look.
These are just some examples to name a few; there is one, however, that if you're not careful will cause a lot of trouble. That's the harness connector used on the 45RFE, 545RFE, and the 68RFE. This connector makes you release two locks before you can move the lever down that holds the connector on. The first one is red and is fairly easy to see, the second is black like the connector itself and if you don't know it's there you will break it off trying to force the holding lever down. If the lock is broken off and you try and reconnect without it, the connector won't stay down, and you soon have a condition like in (figure 4) and lots of DTC's stored in the computer.
(Figure 5) shows a connector with the lock broken off; (figure 6) shows what it looks like the way it should be.
(Figure 7) illustrates the first lock, it's the red one and it gets pushed down, it holds the second lock in place and you can't release it until the red one is out of the way.
(Figure 8) shows you the second lock, with the red lock out of the way you can push this lock in and it will release the holding lever, (figure 9). Now simply rotate the holding lever down, and it will lift itself part way off the solenoid block (figure 10).
If that lock is ever broken off, you will need to devise a way to hold the lever securely up in place, and the connector down tight to the solenoid block. If you look inside the connector you will see the weather seal, this has to fit snugly on top of the block connector.
To reconnect, push the connector down until the lever engages the ears on the side on the solenoid block. Rotate the lever all the way up, until it snaps into the lock, this will pull the connector down, now push the red lock back up and you're all done.