Massey Ferguson 4.01.90 – TRANS1: Issue With Speed Sensor Values

The transmission controller is receiving erratic, missing, or out-of-range signals from the transmission speed sensor (often the theoretical forward speed sensor or intermediate speed sensor). Without an accurate speed signal, the transmission cannot properly time its shifts, which can result in rough shifting, poor fuel economy, or the tractor refusing to engage gears.

• 5710SL
• 5711SL
• 5712SL
• 5713SL
• T4
• 7714
• 7715
• 7715S
• 7716
• 7716S
• 7718
• 7718S
• 7719
• 7720
• 7720S
• 7722
• 7722S
• 7724
• 7724S
• 7726
• 7726S

1. 1

   Inspect the wiring harness and connectors between the transmission speed sensor and the TRANS1 module for corrosion, loose pins, or wire chafing caused by vibration.

2. 2

   Disconnect the sensor and measure its resistance with a multimeter. A healthy inductive speed sensor typically reads 450 Ohms (± 20 Ohms) when stopped (some alternate part revisions may read closer to 540 Ohms).

3. 3

   Check for an alternating voltage output from the sensor when the transmission ring gear is rotating.

4. 4

   Ensure the sensor hasn't backed out due to a loose counter-nut, which would increase the air gap and cause signal loss.

1. 1

   Locate the Sensor

   The transmission speed sensor is typically located on the transmission housing, directly above the differential ring gear.

2. 2

   Removal

   Disconnect the electrical harness. Loosen the counter-nut and unscrew the faulty sensor from the housing.

3. 3

   Preparation

   Apply a small amount of thread sealant (e.g., Loctite 5922) to the threads of the new sensor.

4. 4

   Set the Air Gap

   Carefully screw the new sensor in fully until it gently bottoms out against the internal gear. Unscrew the sensor by exactly ¾ of a turn to establish the correct air gap.

5. 5

   Secure

   Hold the sensor in place so it does not rotate, and tighten the counter-nut to approximately 6 Nm.

6. 6

   Reassembly & Clearing

   Reconnect the electrical harness. Use an AGCO Electronic Diagnostic Tool (EDT) to clear the 04.01.90 fault code from the TRANS1 module, then test drive the tractor to verify smooth shifting.