Case IH U37 – Transmission Control Module (TCU) / MTA CCM: Synchroniser potentiometer signal is out of range for the reverse position

The transmission controller is receiving a voltage signal from the synchroniser potentiometer that falls outside the expected calibrated parameters when the transmission attempts to engage the reverse position.

• Maxxum
• Farmall 40
• Farmall 45
• Farmall 50
• Farmall 115U
• MXM Series
• Puma Series
• Maxxum Series

1. 1

   Inspect the synchroniser potentiometer to see if it has been painted over during production, which can interfere with its operation.

2. 2

   Visually inspect the synchroniser potentiometer and its wiring connector for physical damage, corrosion, or swapped connectors.

3. 3

   Check if the synchroniser assembly itself is mechanically very tight or sticky.

4. 4

   Use a voltmeter to check the actual voltage signal coming from the synchroniser potentiometer to verify if it is genuinely out of range.

1. 1

   Locate

   Locate the reverse synchroniser potentiometer on the side of the transmission housing.

2. 2

   Inspect

   Perform visual inspections checking for paint, damaged pins, or wiring harness issues.

3. 3

   Test

   Back-probe the sensor with a voltmeter to monitor the signal voltage.

4. 4

   Calibrate

   If the voltmeter shows that the signal is actually within the acceptable range (indicating the sensor is functioning but the synchroniser is physically sticking), perform a transmission calibration procedure to attempt to free up the sticky synchroniser assembly.

5. 5

   Disconnect

   If the calibration fails, or if the voltmeter confirms the sensor is dead/damaged, disconnect the wiring harness from the potentiometer.

6. 6

   Remove

   Unbolt and remove the faulty synchroniser potentiometer from the transmission.

7. 7

   Install

   Install the new replacement potentiometer and reconnect the wiring harness.

8. 8

   Calibrate

   Run the tractor's electronic transmission calibration procedure (often accessed via the H-Menu on the dash) so the TCU can learn the new potentiometer's voltage values for the forward, neutral, and reverse positions.