785G Off-Highway Truck Systems Caterpillar


Calibration - Transmission Control (Shift Lever)

Usage:

785G RTL

Introduction

This calibration procedure must be performed under the following conditions:

  • The initial assembly of a new machine

  • The replacement of the shift lever assembly

  • The replacement of the shift lever sensor

  • The replacement of the Transmission ECM

  • An ECM that is exchanged between machines

There are variations in shift levers from the factory. Because of these variations, the position of first gear and the position of second gear may overlap. The ECM automatically determines the detent for first gear by looking for a stable duty cycle. This duty cycle will be a lower duty cycle than the current duty cycle used for first gear. When a stable duty cycle is read, the ECM uses the stable value as the new first gear position. The ECM adjusts the position for second gear accordingly.

Test Procedure

Shift Lever

This automatic process will not detect the correct first gear detent if new shift lever hardware is installed on the machine. The automatic process will not detect the correct first gear detent if the ECM has been replaced. Therefore, a manual procedure to reset the calibration back to the default is required.

Use the following procedure to reset the shift lever calibration back to the factory default value. Use the following procedure to calibrate the ECM to the shift lever that is installed on the machine.

  1. Place the shift lever in the neutral position.

  2. Depress the selector switch for the top drive gear for 15 seconds.

  3. Release the switch for the top drive gear.

  4. Move the shift lever to the first gear position.

  5. Leave the shift lever in the first gear position for 1 second.

Transmission Clutch

Use Cat® ET to calibrate the transmission clutch pressures. The procedures are performed to compensate for variations in the transmission components.

Note: The torque converter lockup clutch calibration procedure is performed during the calibration procedure for the six transmission clutches.

Calibration is required in the following situations:

  • Before dealer delivery to the customer

  • After replacing the Transmission ECM

  • After replacing or servicing any of the ECPC valves or the main relief valve

  • After replacing or rebuilding the transmission or torque converter

  • After replacing the transmission charge pump

  • Degradation in shift quality

The Transmission ECM must detect the following conditions before starting the calibration procedure:

  1. The parking brakes are ENGAGED.

  2. The service brakes are RELEASED.

  3. The engine speed is at low idle (approximately 700 rpm).

  4. The gear selector is in the PARK position.

  5. The transmission oil temperature is above 70 °C (158 °F) and below 85 °C (185 °F).

  6. The transmission output speed (TOS) is 0 rpm.

  7. There are no active clutch solenoid diagnostic codes.

  8. There are no active transmission or torque converter speed sensor diagnostic codes.

  9. There are no active transmission or torque converter temperature sensor diagnostic codes.

If any of these conditions are not met during the calibration, the procedure is aborted immediately.

The sustain pressure calibration requires pressure gauges to measure the actual pressure in the clutch. The Data View diagnostic tool should be used when possible. Seven pressure gauges should be installed before the calibration procedure begins. The transmission ECPC valve pressure taps are on the cover of the transmission and the lockup clutch (LUC) ECPC is on the torque converter case.



Illustration 1g06231384

Select the Transmission ECM from the list of available modules.



Illustration 2g06231387

Select "Service" from the tool bar and "Calibrations" on the drop-down menu.



Illustration 3g06231391

When the window opens, select Transmission Clutch Engagement Pressure Calibration, under the Transmission ECM listing.



Illustration 4g06231393

Check the box next to each of the calibration options listed.



Illustration 5g06231395

Read and follow the instructions (Shown in bold). After each instruction is completed, click "NEXT" in the lower left corner of the screen.



Illustration 6g06231399

Read and follow the instructions (shown in bold). After each instruction is completed, click "NEXT" in the lower left corner of the screen.



Illustration 7g06231400

Read and follow the instructions (shown in bold). Read the pressure on the pressure gauges installed earlier. Click "NEXT" in the lower left corner of the screen.

Use the Cat ET to increase the individual pressure of the clutch. Use Cat ET to decrease the individual pressure of the clutch. The pressure changes can be viewed on the pressure gauge.

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