HELP! Strange reverse problem, 5HP24

[dshealey]

I have a 5hp24 transmission, which I rebuilt about a year ago. I have a sudden loss of reverse, with no warning. Drives perfectly in forward.

I have used INPA and DIS to monitor everything, and there are no error codes in the car anywhere.

The strange thing is that the the three shift solenoid signals from the EGS controller are wrong only in reverse, solenoid 2 should be on, 1 and 3 off, but only solenoid 1 is on. I put LEDs on the three solenoid lines to be sure, and they prove that this is the case. I drove the car with the LEDs and the solenoids are switched on/off properly in all gears except reverse.

I tried a second EGS controller from the same model and year car, same results.

INPA also shows that the shift switch lines 1 through 4 are correct for all positions of the shifter, so that seems to be working perfectly.

When I select Reverse, shift switch line 1 only is on, correct, but the controller is only turning on solenoid 1, when it should be solenoid 2!

I am feeling that this is a control problem, not something in the transmission, and want to get the electrical issue resolved first before thinking something inside the transmission has failed.

I have spent many hours searching the internet, on multiple forums of cars that use this transmission, and so far seem to have the only instance of this issue ever.

Does anyone have any input as to why two different EGS controllers would have the same problem (correct shift switch inputs, incorrect solenoid outputs)?