621H, 623H and 627H Wheel Tractor-Scrapers Power Train Caterpillar

Before you begin the checks, refer to "Testing and Adjusting" section of Systems Operation, Testing and Adjusting, "Machine Preparation for Troubleshooting".

Check 1

This check will determine the following three items.

• The scraper selection spools may be manually moved through all of the positions.

• The scraper selection spools may move when the electrical system operates correctly.

• The scraper selection spools may move when the hydraulic system operates correctly.

Procedure for Manual Shifting

The speed selector spool can be manually moved through all positions when the scraper engine is off.

1. Put a wrench on the selection shaft. Rotate the wrench counterclockwise until the wrench stops. The scraper transmission is now in REVERSE.

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Illustration 1	g01033404
Location of the scraper transmission selection shaft

2. From the REVERSE position, rotate the wrench clockwise through all detent positions of the selector shaft. The positions from REVERSE are NEUTRAL, FIRST, SECOND, THIRD, and FOURTH speeds.

   Note: There is approximately 10 degrees of rotation between each detent of the cam.

Procedure

Machine condition: DO NOT START THE ENGINE. THE BATTERY DISCONNECT SWITCHES FOR THE TRACTOR AND THE SCRAPER ARE IN THE OFF POSITION. THE ENGINE START SWITCH IS IN THE OFF POSITION.

1. Prepare to manually shift the transmission. Refer to "Procedure for Manual Shifting"above.

2. Manually shift the transmission through all speed positions.

3. Turn the rotary selector spool to the NEUTRAL position.

Result

• The selection shaft will rotate through all of the speed positions. Proceed to the next step.

• If the selection shaft will not rotate through all of the speed positions, check for the following conditions.

• Foreign material does not allow movement of the selection spools.

• Damage will not allow movement of the selection spools.

Check 2

This check will determine the following conditions:

• The electronic transmission control module for the scraper has power.

Procedure

Machine condition: DO NOT START THE ENGINE. THE BATTERY DISCONNECT SWITCHES FOR THE TRACTOR AND THE SCRAPER ARE IN THE ON POSITION.

Result

• If the electronic transmission control module for the scraper is ON, proceed to the next step.

• If the electronic transmission control module for the scraper is OFF or a fault code is detected, check the electrical system. Refer to Electrical System Schematic, and Wheel Tractor-Scraper Power Train Electronic Control System, Systems Operation, Troubleshooting, Testing and Adjusting.

Check 3

This check will determine the following conditions:

• The scraper transmission neutral/run control is operating correctly.

Procedure

Machine condition: THE TRACTOR ENGINE IS IN THE ON POSITION. THE SCRAPER ENGINE IS IN THE ON POSITION. THE SCRAPER TRANSMISSION NEUTRAL/RUN CONTROL IS IN THE ENGAGED POSITION.

1. Place the transmission control in the FIRST speed position.

2. Depress the governor control pedal for the scraper engine.

Result

• If the machine moves forward, proceed to the next step.

• If the machine does not move forward, check the electrical system. Refer to Electrical System Schematic, and Wheel Tractor-Scraper Power Train Electronic Control System, Systems Operation, Troubleshooting, Testing and Adjusting.

Check 4

This check will determine the following conditions:

• The electrical signal is delivered to the synchronizing solenoid.

• The synchronizing solenoid activates electrically.

• The ground verify that wires are connected to the machine ground.

Procedure

Machine condition: THE ENGINE IS IN THE OFF POSITION. THE BATTERY DISCONNECT SWITCH IS IN THE ON POSITION. THE ENGINE START SWITCH IS IN THE ON POSITION.

1. Position the transmission control lever and the rotary actuator for the tractor in the NEUTRAL position. DO NOT START THE ENGINE.

2. Disconnect the harness connector for the synchronizing solenoid from the synchronizing solenoid.

3. Make contact with the harness connector for the synchronizing solenoid to the synchronizing solenoid. When the connector makes contact to the synchronizing solenoid, a clicking or a buzzing noise will occur.

4. When the check is complete, connect the harness connector for the synchronizing solenoid to the synchronizing solenoid.

Result

• If the click is heard or the buzz is felt, then proceed to the next step.

If there are no clicking or buzzing, perform the following checks:

• Check that the synchronizing solenoid is not bad.

• Check that the ground verify wires in order to ensure that there are no electrical problems. Refer to Electrical System Schematic, and Wheel Tractor-Scraper Power Train Electronic Control System, Systems Operation, Troubleshooting, Testing and Adjusting.

• Check the wire to the synchronizing solenoid in order to ensure that the wire is not open or broken. Refer to Electrical System Schematic, and Wheel Tractor-Scraper Power Train Electronic Control System, Systems Operation, Troubleshooting, Testing and Adjusting.

• Check the harness to the synchronizing solenoid in order to ensure that the harness is not open or broken. Refer to Electrical System Schematic, and Wheel Tractor-Scraper Power Train Electronic Control System, Systems Operation, Troubleshooting, Testing and Adjusting.

Check 5

This check will determine the following conditions:

• The electrical signal is delivered to the downshift solenoid.

• The downshift solenoid activates electrically.

• The ground verify that wires are connected to the machine ground.

Procedure

Machine condition: THE ENGINE IS IN THE OFF POSITION. THE BATTERY DISCONNECT SWITCH IS IN THE ON POSITION. THE ENGINE START SWITCH IS IN THE ON POSITION.

1. Position the transmission control lever and the rotary actuator for the tractor in the FIRST speed position. DO NOT START THE ENGINE.

   Note: At this time, the scraper transmission is not synchronized with the tractor transmission. The downshift solenoid will be activated in order to shift the scraper transmission into the NEUTRAL position.

2. Disconnect the harness connector for the downshift solenoid from the downshift solenoid.

3. Make contact with the harness connector for the downshift solenoid to the downshift solenoid. When the connector makes contact to the downshift solenoid, a clicking or a buzzing noise will occur.

4. When the check is complete, connect the harness connector for the downshift solenoid to the downshift solenoid.

Result

• If the click is heard or the buzz is felt, then proceed to the next step.

If there are no clicking or buzzing, perform the following checks:

• Check that the downshift solenoid is not bad.

• Check that the ground verify wires in order to ensure that there are no electrical problems. Refer to Electrical System Schematic, and Wheel Tractor-Scraper Power Train Electronic Control System, Systems Operation, Troubleshooting, Testing and Adjusting.

• Check the wire to the downshift solenoid in order to ensure that the wire is not open or broken. Refer to Electrical System Schematic, and Wheel Tractor-Scraper Power Train Electronic Control System, Systems Operation, Troubleshooting, Testing and Adjusting.

• Check the harness to the downshift solenoid in order to ensure that the harness is not open or broken. Refer to Electrical System Schematic, and Wheel Tractor-Scraper Power Train Electronic Control System, Systems Operation, Troubleshooting, Testing and Adjusting.

Check 6

This check will determine the following conditions:

• The Electrical signal is delivered to the upshift solenoid.

• The upshift solenoid activates electrically.

• The ground verify that wires are connected to the machine ground.

Procedure

Machine Condition: THE ENGINE IS IN THE OFF POSITION. THE BATTERY DISCONNECT SWITCH IS IN THE ON POSITION. THE ENGINE START SWITCH KEY IS IN THE ON POSITION.

1. Maintain the conditions that were stated in "Check 5":
   • The transmission control is in the REVERSE position.

   • The rotary selector spool is in the REVERSE position.

   • The battery disconnect switch is in the ON position.

   • The engine start switch is in the ON position.

   • DO NOT START THE ENGINE.

   Note: At this time, the scraper transmission is not synchronized with the tractor transmission. The upshift solenoid will be activated in order to shift the scraper transmission into the NEUTRAL position.

2. Place the transmission control lever in REVERSE.

3. Disconnect the harness connector for the upshift solenoid from the upshift solenoid.

4. Make contact with the harness connector for the upshift solenoid to the upshift solenoid. When the connector makes contact to the downshift solenoid, a clicking or a buzzing noise will occur.

5. When this check is complete, connect the harness connector for the upshift solenoid to the upshift solenoid. Place the transmission control lever in NEUTRAL.

Result

• If a clicking or a buzzing occurs, refer to Electrical System Schematic, and Wheel Tractor-Scraper Power Train Electronic Control System, Systems Operation, Troubleshooting, Testing and Adjusting.

If a clicking or a buzzing does not occur, perform the following checks:

• Check that the downshift solenoid is not bad.

• Check that the ground verify wire in order to ensure that the wire is not open or broken. Refer to Electrical System Schematic, and Wheel Tractor-Scraper Power Train Electronic Control System, Systems Operation, Troubleshooting, Testing and Adjusting.

• Check if the wire to the upshift solenoid is open or broken. Refer to Electrical System Schematic, and Wheel Tractor-Scraper Power Train Electronic Control System, Systems Operation, Troubleshooting, Testing and Adjusting.

• Check if the harness to the upshift solenoid is open or broken. Refer to Electrical System Schematic, and Wheel Tractor-Scraper Power Train Electronic Control System, Systems Operation, Troubleshooting, Testing and Adjusting.

Check 7

This check will determine the following conditions:

• The scraper transmission will operate in all speeds.

• The transmission clutches engage smoothly in all speeds.

Note: This check must be performed after you remove both of the drive axles from the scraper. Refer to the Power Train, Disassembly and Assembly, "Axles" for more information on removing the drive axles. When you remove the drive axles, check the level of the oil in the differential and bevel gear case. Check the oil level when the scraper transmission is operated.

Procedure

Machine Condition: THE ENGINE IS IN THE OFF POSITION. THE BATTERY DISCONNECT SWITCH IS IN THE OFF POSITION. THE ENGINE START SWITCH IS IN THE OFF POSITION. THE PARKING BRAKES ARE ENGAGED.

1. Remove the harness connector from the position sensor (speed) for the scraper.

   Note: When you remove the harness connector, the electronic transmission control module for the scraper will keep the upshift solenoid activated.

2. Remove the harness connectors from the upshift solenoid, the downshift solenoid, and the synchronizing solenoid.

3. Connect the harness connector for the upshift solenoid to the synchronizing solenoid.

   Note: The harness connector for the upshift solenoid will keep the synchronizing solenoid active during this test so that the scraper transmission can be manually shifted.

4. Turn the battery disconnect switch to the ON position. Turn the engine start switch to the ON position.

5. Start the scraper engine. Operate the scraper engine at LOW IDLE rpm.

6. Put the 8H-8501 Open End Wrench on the selection shaft for the scraper transmission.

7. Move the selection shaft for the scraper transmission from the NEUTRAL position to the FOURTH speed position. The transmission will shift into all speeds.

8. When this check is complete, place the selection shaft for the scraper transmission back into the NEUTRAL position.

9. When this check is complete, place the harness connectors back into the proper locations.

Result

• If the scraper transmission misses a shift in one or more speed positions, the transmission hydraulic system is malfunctioning. Refer to "Testing and Adjusting" section of Systems Operation, Testing and Adjusting for more information about testing the transmission hydraulic systems.

Check 8

This check will determine the following conditions:

• The final drives are operating correctly.

• There is no damage to the final drives.

• The differential and final drives are operating correctly.

Procedure

Machine Condition: THE ENGINE IS IN THE OFF POSITION. THE BATTERY DISCONNECT SWITCH IS IN THE OFF POSITION. THE ENGINE START SWITCH IS IN THE OFF POSITION.

1. Drain the final drives. Remove the covers on the final drives.

2. Inspect the final drives for wear or damage. Inspect the final drive case for metal chips.

3. Drain the differential and bevel gear case.

4. Inspect the bottom of the differential case for metal chips.

5. Lift the rear of the machine until one wheel does not touch the ground.

6. Rotate the wheel backward and rotate the wheel forward in order to check the backlash of the differential. Refer to "Testing and Adjusting" section of Systems Operation, Testing and Adjusting, "Differential and Bevel Gear - Adjust".

Result

• If there is damage to the final drives, you must repair the final drives.

• If there are metal chips in the bottom of the differential case, you must repair the differential or bevel gear.

• If the backlash of the differential is out of the specification, refer to "Testing and Adjusting" section of Systems Operation, Testing and Adjusting, "Differential and Bevel Gear - Adjust".