Having just discovered that I have a 4l80e harness, I'm working to fix it so that it will properly control my 4l60e transmission. so far what I've got is that I need to switch pin "S" to "U" on the trans connector, which is connected to #2 red on the PCM, then add a pin from #42 Red to "T" on the transmission, and #79 blue gets pinned into pin "S".
Anyone who's gone the opposite direction able to confirm? I was a little worried, but if its this simple I'm feeling pretty good about that actually, just want to make sure I'm not over simplifying.