953D, 963D and 973D Track-Type Loaders Machine Moves Slowly Caterpillar


Machine Moves Slowly
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1.1. Probable Causes
2.1. Recommended Actions
3.2. The Fuel Efficient Reverse (FER) Is Set Incorrectly
4.2. The Engine RPM Is Set Too Low
5.2. The Control Lever Is Not Calibrated Properly
6.2. The Steering Pedal Position Sensors Are Not Calibrated Properly
7.2. There Is An Excessive Load In The Undercarriage
8.2. The Operator Preferences Setting For The Implement Response Is Set Too Fast
9.2. The Machines Max Speed Setting Is Set Incorrectly
10.2. Hystat System Pressure Is Not Correct
11.2. Failed Brake Components
12.2. The Pump Control is Suspect
13.2. The Pump Has Too Much Wear
14.2. The Hystat Pump Or The Hystat Motor Has Failed

Probable Causes

  • The fuel efficient reverse (FER) is set incorrectly

  • The engine rpm is set too low.

  • The control lever is not calibrated properly.

  • The steering pedal position sensors are not calibrated properly.

  • There is an excessive load in the undercarriage.

  • The operator preferences setting for the implements are set too fast

  • The machines max speed setting is set incorrectly.

  • Hystat system pressure is not correct.

  • Failed brake components

  • The pump control is suspect.

  • The pump has too much wear.

  • The hystat pump or the hystat motor has failed.

Recommended Actions

The Fuel Efficient Reverse (FER) Is Set Incorrectly

If running the machine in "Fuel Efficient Reverse" (FER) mode then the speed of the implements when engaged will be lower. You can disable the function if you need more implement speed.

The Engine RPM Is Set Too Low

Increase the engine rpm setting. Guidelines for checking the engine rpm refer to the Testing and Adjusting manual for the engine in your machine.

The Control Lever Is Not Calibrated Properly

Be sure that the control lever position sensor is calibrated properly. Refer to Testing and Adjusting, "Hystat Operator Control Calibrations" for your machine.

The Steering Pedal Position Sensors Are Not Calibrated Properly

Be sure that the steering pedal position sensors are calibrated properly. Refer to Testing and Adjusting, "Hystat Operator Control Calibrations" for your machine.

There Is An Excessive Load In The Undercarriage

Inspect the undercarriage of the machine for excessive debris buildup. If there is excessive debris then clean the undercarriage system. Make sure it is operating under a normal load.

The Operator Preferences Setting For The Implement Response Is Set Too Fast

Use Messenger to set the "Implement Response" setting to a lower setting.

The Machines Max Speed Setting Is Set Incorrectly

Check the "Max Speed" setting in ET. Change the setting to the appropriate speed that meets your demands.

Hystat System Pressure Is Not Correct

Check the system pressure. Refer to Testing and Adjusting, "Relief Valve - Test and Adjust" for your machine.

Failed Brake Components

Disassemble the brakes and check the following components of the brakes for failure:

  • seals

  • splines

  • friction discs

  • brake plates

Replace any damaged components, if necessary.

Calibrate the hystat operator controls. Refer to Testing and Adjusting, "Hystat Operator Control Calibrations" for your machine.

The Pump Control is Suspect

Make sure that the "Flow Rate" for the hydraulic control valve is adjusted correctly. Refer to Testing and Adjusting, "Hydraulic Pump - Test and Adjust" for your machine.

Check the current that is applied to the solenoid valve. Make sure that the solenoid valve is functioning correctly.

If necessary, repair the solenoid or replace the solenoid valve.

The Pump Has Too Much Wear

Refer to Testing and Adjusting, "Hydraulic Pump - Test and Adjust" for your machine.

The Hystat Pump Or The Hystat Motor Has Failed

Ensure that the hystat motor is not worn to the point that the steering system cannot maintain the correct pressures. Wear to the hystat motor rotating group may cause excessive internal (case drain) leakage. This condition may cause the hystat motor to operate inefficiently, which results in wider (less sharp) turns, excessive noise while steering, low steering or charge pressures, and hesitation prior to turns.

  1. Start the engine and run the engine.

    ENSURE THAT THE SERVICE BRAKES ARE FULLY APPLIED THROUGHOUT THIS ENTIRE PROCEDURE.

    WARNING: The machine may move during this procedure if the service brakes are released or if the service brakes are weak. When you move the steering control lever during this procedure, ensure that all personnel are positioned so that no injury can occur due to machine movement.

    Warm the hydraulic oil to 65°± 3°C (150°± 5°F).

  2. Stop the engine and disconnect hydraulic hose from the fitting on the manifold of the case drain for the hystat motor.

  3. Place the end of the hose in a suitable container with a known volume such as a 5 gallon bucket.

  4. Install a plug at the fitting on the case drain manifold in the same place that the line for the case drain was attached to the hystat motor.

  5. Start the engine and set engine speed to HIGH IDLE.

    • 953D and 963D 2000 rpm

    • 973D 1900 rpm

  6. Move the steering lever to the full LEFT TURN position and hold it long enough to determine the case drain flow rate. Repeat this step in the full RIGHT TURN position.

    The motor's case drain flow rate in each direction should be approximately 4 L/min (1 gpm) in either direction.

    1. If the motor's case drain flow rate is no more than 20% of the specification, the motor is capable of attaining the speed/pressure specifications.

    2. If the motor's case drain flow rate is significantly greater when steering one direction than the other, either a cross port leak (on the pressurized side) is present or the flushing valve is stuck in one position. (A cross port leak can cause the machine to drift from straight travel.)

    3. Replace the motor if the flow rate is more than 20% above this specification. The motor is worn and leaking too much. Retest the system after the motor is replaced.

  1. Check The Hystat Motor Output Shaft Seal For Damage Or Wear.

    Damage to or excessive wear of the seal around the hystat motor output shaft can allow hydraulic oil (case drain) to leak past the shaft seal.

    1. Remove the hystat motor from the bore in which it is installed and wiggle the shaft to see if there is any movement.

      If the shaft does not wiggle, disconnect and remove the hystat motor from the machine and bench test the motor.

    2. Operate the motor at 425 psi in both directions. Observe the shaft seal during bench test operation and look for signs of leakage. If leakage is observed replace the shaft seal. Carefully examine the shaft for damage where the seal and shaft contact each other. After repair and assembly, test the motor again and look for leakage at the shaft before reinstalling the motor.

      If the shaft is loose, worn or failed bearings have allowed the shaft to cause wear to the shaft seal.

    3. Disassemble The Hystat Motor And Inspect For Damage

      If it has been determined that the hystat motor has excessive internal wear or damage, disconnect the hydraulic lines and the electrical harness from the motor and remove the motor from the machine. Disassemble the motor and carefully examine all internal parts (port plates, rotating group, bearings, etc.). Replace any worn or damaged parts as necessary and bench test, or replace the worn/damaged motor with a new motor.