Problem just started. I have only owned this for a few months but it did shift normally before. When in Overdrive, Drive, 1-2, transmission starts out in low range but wont shift until speed reaches 35 mph then it shifts hard to second gear, but doesn't shift to third or overdrive. The transmission does not seem to be slipping while accelerating but when I let off the gas it does not slow down as I would expect, but is almost as if it is coasting. When you give it enough gas that the engine speed reaches the speed of travel it starts to accelerate again.
I have dropped the transmission pan, replaced pickup screen that wasn't all that dirty. Fluid is clean, not burned yet. Removed the three solenoid valves replaced the O-rings on the end of the valves. Checked valves to insure they opened & closed with battery volts applied. Installed fresh ATF. All valves work as I would expect. Removed what I think is a speed sensor in the tailshaft, located above the speedometer cable, that makes & breaks continuity when a magnet is past near the sensor.
I have a Haynes manual for the unit but the wiring diagrams don't include transmission control circuit.
Anyone with any ideas, info on how the electronics controls work for transmission shifts. Could someone tell me if another trans. could be installed, perhaps a Torqueflight that might bolt up to the 4.0 engine.