Common Problem #3: Poor Electrical Connections
Aside from delayed shifts in certain gears, the 47RE is even known to hop around sporadically to different gears, and its torque converter is known to jump in and out of lockup (the point where the engine and transmission settle on the more “constant” speed after accelerating). This is due to poor electrical connections to the PCM and interference from other electrical components under the hood. One notorious source of lockup failure is the main ground wire to the PCM, which faces interference from the alternator as the wire runs near it. The factory material on the wire isn’t thick enough to shield electromagnetic interference, thus what happens is that the PCM picks up on the alternator and distributes the wrong voltage to the transmission solenoids. The PCM then confuses itself and keeps trying to shift to a higher gear when it has already gone through all of them. At that point, the converter can only go into lockup. This problem can be an easy fix, though. To fix it, grab some sheets of aluminum foil, cut them into smaller pieces, and wrap them around the ground wire with electrical tape. The ground wire can be identified by its black shield with a yellow stripe. When done, pull the ground wire back out of the way of the alternator.
“Another way to fix this problem is to re-ground the alternator,” adds Willsey.