Case IH 81 – Transmission Controller (TRANS / TCU): The transmission clutches are slipping

The controller detects a discrepancy between the expected transmission output speed and the actual output speed, which points to either physical clutch slippage or an erratic/failing signal from the transmission output speed sensor.

• MX Magnum
• STX Steiger
• Steiger 330
• Steiger 350
• Steiger 450
• Steiger 535
• STX series
• MX Magnum Series
• TG Series

1. 1

   Measure the resistance value of the transmission output speed sensor. The correct specification is between 2700 and 3300 ohms.

2. 2

   Check Sensor Adjustment: Turn the sensor all the way in until it bottoms out on the shaft. Ensure that paint or debris on the threads does not prevent the sensor from threading in completely. Back the sensor outward exactly 1/8 to 1/4 turn and tighten the lock nut.

3. 3

   Connect the Electronic Service Tool (EST) and view the 'Trans Transmission Output Speed' reading. Observe if the reading stays steady or if it becomes erratic/drops off while moving. Record and save the data in 0.1-second intervals.

4. 4

   Evaluate the Speed Ring: If the sensor is adjusted correctly and tests within the proper resistance range, but the EST readings are still not steady, the speed ring (tone ring) for the sensor is out of tolerance (excessive run-out).

1. 1

   Remove assembly

   Remove the coupling flange and speed pick-up ring assembly from the transmission output.

2. 2

   Machine speed ring

   Mount the speed ring in a lathe and machine it to correct the run-out.

3. 3

   Clean debris or replace parts

   Ensure all metal debris and burrs are completely removed after the speed ring is trued in the lathe. (Note: If machining is not an option, replace the coupling flange and speed pick-up ring with new OEM parts).

4. 4

   Reinstall assembly

   Reinstall the coupling flange and speed ring assembly.

5. 5

   Reinstall sensor

   Reinstall the transmission output speed sensor. Thread it in until it stops, then back it out 1/8 turn and secure the lock nut.

6. 6

   Clear fault code

   Clear the fault code using the EST or monitor.

7. 7

   Test drive

   Test drive the tractor. Engage each gear to determine if the fault returns. Pay close attention to abnormal noises or sluggish gear engagement, which would indicate actual internal clutch pack failure requiring a transmission teardown.