785G Off-Highway Truck Systems Caterpillar

Show/hide table

Personal injury or death can result from sudden machine movement. Sudden movement of the machine or release of air pressure or oil pressure can cause injury to persons on or near the machine. To help prevent possible injury before testing and adjusting any air system or hydraulic system, perform the procedure in the Testing and Adjusting, "General Information" section.

Specifications

Introduction

The following instructions will provide adequate information to test and adjust the calibration of supply pressure for the torque converter lockup clutch.

Note: Make sure that the filters and the screens are clean before you test any pressures. Make sure that the oil is at operating temperature before you perform this test.

Required Tools

Illustration 1	g02581096
Tooling (B) 317-7484 Communication Adapter III

Test Preparation

1. Move the machine to a smooth horizontal location. Move away from any machines that are working and any personnel.

2. Move the transmission control to the P position. Fully raise the dump body of the truck.

3. Install the retaining pin for the dump body.

4. Stop the engine.

5. Permit only one operator on the machine. Either keep other personnel away from the machine, or keep other personnel in the sight of the operator.

6. Place blocks in front of the wheels and behind the wheels.
   Show/hide table

   Illustration 2	g06194374
   View of the rear of the torque converter on the 785G. The pressure tap for the modulating valve is indicated by the arrow.

7. Connect tooling (A) onto pressure tap (2).

8. Connect tooling (B) to the service connector in the cab.

Test Procedure

Show/hide table

Illustration 3	g06231573

1. Start Cat ET. Choose "Transmission 785" from the list, and click "OK".
   Show/hide table

   Illustration 4	g06231575

2. From the tool bar, select "Service" then "Calibrations".
   Show/hide table

   Illustration 5	g06231577

3. Select the "Transmission Clutch Engagement Pressure Calibration" and click "Start".
   Show/hide table

   Illustration 6	g06231798

4. Select "Lockup Clutch Engagement Pressure Calibration" and click "Begin".
   Show/hide table

   Illustration 7	g06231585
   View of Calibration screen

5. Connect Tooling (A) to valve to be calibrated. Click the next button after the gauge is connected.

6. When the setup conditions are met, click the "Next"button to continue.

Adjustment Section

Illustration 8	g06231590

1. View tooling (A) to view the lockup clutch engagement pressure. The target pressure is controlled through the Cat ET screen. Adjust the current by using the increment and decrement buttons to select the target value. Observe the change in the value that is displayed on tooling (A) until the target value is achieved.

2. After the correct pressure is reached, click "Next".

3. The window that pops up should show a "CALIBRATION SUCCESSFUL" message.

4. Click "Finish" to complete the calibration.

5. Turn off the machine and remove all test equipment.

Note: If the calibration results in failure, refer to the section within this manual called "Transmission Fill - Calibrate" to troubleshoot the transmission clutches.