Sorry for the long post, but It all started couple of weeks ago, my truck all of a sudden stopped down shifting, so I replaced the gov pressure sensor and put in a new borgwarner solenoid and it fixed it, then we went camping that weekend and towed my trailer up the mountain and had no problem, but then on our way back it started doing it again. So I drove it home the rest of the way pretty much in third gear, (it does shift out of overdrive by itself) started thinking maybe it was something in the valve body. So when I got home I figured it was a good time to finally tear it down and build it bad ***. So I did and we got it all back together and took it out for a drive and guess what, still wont down shift, when we had it apart we replaced the governer pressure solenoid with a gm one, so I just replaced the wiring harness in the tranny to the sensor and solenoid tonight and got it all back together again and it still wont down shift. I can play with it manually and get it to down shift when I come to a stop but not by itself. Anymore thoughts?