Case 385 Transmission error codes

[darindarin]

I lost ability to shift powershift transmission. I get TRANS 75 error code: "TRANS 75 Engine speed from Inst Controller does not match the speed signal from the alternator.". I was told this was due to faulty shaft speed sensor on left hand back side of transmission or the wiring harness itself. I checked the continuity of every wire in the harness. I also did a power probe check of the sensor wires and they test OK. The voltage to the sensors is 5V. I removed the sensors and did a bench test. I do not have the specs for them but they are all functional. I checked my alternator and it is putting out 120 Amps with all accessories on. There is 22 Amps going to the fuse box. The only sensor I did not test yet is 5th shaft sensor on right hand side of transmission. From what I understand it detects RPM and I believe the RPM registered on the display. I recently replaced the Arm rest controller because it lost all functionality. Doing so did not solve the issue I had at the time. All fuses are good.
Edit: I tested the 5th shaft sensor wire and it is only putting out 4.3V when all all sensors receive 5.0V.
Any ideas of where the problem lies?