Massey Ferguson 04.X.31 – TRANS: Transmission Hydrostatic Speed/Direction Sensor Issue

The sensor responsible for monitoring the speed and rotational direction of the hydrostatic drive unit within the transmission is sending erratic, out-of-range, or missing signals to the computer. This can result in erratic shifting, loss of speed readouts, or the tractor refusing to move.

• 7714
• 7715
• 7715S
• 7716
• 7716S
• 7718
• 7718S
• 7719
• 7720
• 7720S
• 7722
• 7722S
• 7724
• 7724S
• 7726
• 7726S
• Tier 4 (2015-2021)
• 7700
• 7700S
• 6400
• 6600
• 6700
• 7400
• 7600
• 8400
• 8600

1. 1

   Inspect the wiring harness leading to the transmission speed sensor for chafing, breaks, or damage caused by field debris or vibration.

2. 2

   Disconnect the sensor and check the pins for moisture intrusion or corrosion. Clean any corrosion and ensure the weather seal is intact.

3. 3

   Ensure the sensor is tightly bolted to the transmission housing, as excessive vibration from a loose bolt can cause erratic readings.

4. 4

   Check the transmission/hydraulic fluid level and condition. Heavily contaminated fluid or metal shavings can interfere with the magnetic pickup of the speed sensor.

1. 1

   Locate the Sensor

   Locate the hydrostatic speed/direction sensor on the transmission housing (typically mounted externally on the side of the transmission block reading the input/collecting shaft).

2. 2

   Clean the Area

   Thoroughly clean the area around the sensor to prevent dirt from falling into the transmission housing when the sensor is removed.

3. 3

   Disconnect

   Unplug the electrical wiring harness connector from the sensor.

4. 4

   Remove the Sensor

   Remove the single retaining bolt holding the sensor in place and carefully pull the sensor straight out of the housing.

5. 5

   Install the New Sensor

   Lubricate the O-ring on the new sensor with clean transmission fluid. Push it firmly into the port until seated.

6. 6

   Secure and Reconnect

   Reinstall the retaining bolt (do not overtighten, as the sensor body is often plastic). Reconnect the electrical harness, ensuring it clicks into place.

7. 7

   Calibration/Reset

   Use a diagnostic tool to clear the 04.X.31 fault code from the TRANS module. Some transmission systems may require a brief calibration or test drive to sync the new sensor readings.