Case IH 2640 (6153.14) - DEC – DEC: Unwanted engaged or disengaged of Synchro 2

The transmission controller has detected that the #2 synchronizer is not in its calibrated or commanded position. The synchronizer is either moving out of gear unexpectedly (disengaging) or attempting to engage without a command. This is typically accompanied by a failure to move, or a grinding noise followed by a harsh "bang" as the synchronizer eventually forces engagement.

• MAXXUM T4E
• Magnum Series (e.g., Magnum 210, 215, 235, 245, 250)
• Maxxum / MX Series (e.g., MX110, MX120, MX135, MX150, MX170)
• Puma Series
• Farmall Series

1. 1

   Check Position Sensor Voltages: Access the tractor's "HH" diagnostic menus (via the instrument cluster or AFS Pro display) to monitor the synchronizer movement and position sensor voltages. Verify that the synchronizers are moving through their full travel ranges and that the Synchro 2 position sensor is not dropping voltage erratically.

2. 2

   Perform a Transmission Calibration: Run a full transmission calibration. Compare the new calibration values to the previous ones to see if the Synchro 2 values have changed significantly, which indicates mechanical wear.

3. 3

   Check Transmission System Pressure: Verify the transmission system pressure (often visible on the A-Post display on older models or the Pro 700 display on newer ones) to ensure a hydraulic pressure drop isn't causing the synchro to slip.

4. 4

   Inspect the Transmission Filter: Remove the transmission filter cover and inspect it for fine silver grinding or metal shavings. If metal is present, the synchronizer teeth are likely broken or severely worn, necessitating a mechanical rebuild.

1. 1

   Drain Fluids

   Drain the transmission oil.

2. 2

   Split the Tractor

   The tractor must be split at the transmission housing to access the synchronizer assemblies.

3. 3

   Remove the Gear Cover

   Remove the reverse gear cover/transmission housing to expose the synchronizers and clutch packs.

4. 4

   Inspect Synchro 2 and Clutches

   Inspect Synchro 2 for broken teeth or visible signs of wear on the engagement teeth. Inspect the associated clutches (e.g., Clutch A and B) for heat discoloration or damage.

5. 5

   Replace Components

   Replace the damaged Synchro 2 assembly, the synchronizer ring, and any discolored clutch discs. If the position sensor was reading erratically during diagnostics, replace the Synchro 2 position sensor.

6. 6

   Reassemble and Refill

   Reassemble the transmission housing, replace the transmission filter, and refill the system with CNH MAT 3540 specification transmission oil.

7. 7

   Recalibrate

   Perform a final transmission calibration using the EST (Electronic Service Tool) or the in-cab HH menus to teach the DEC the new synchronizer positions.