Pump Servo Neutral - Adjust
SMCS Code: 5261-025
Fixed Frequency and Variable Frequency
Personal injury or death can result from sudden machine
Sudden movement of the machine can cause injury to
persons on or near the machine.
To prevent injury or death, make sure that the area around
the machine is clear of personnel and obstructions before
operating the machine.
Care must be taken to ensure that fluids are contained
during performance of inspection, maintenance, testing,
adjusting and repair of the machine. Be prepared to
collect the fluid with suitable containers before opening
any compartment or disassembling any component
Refer to Special Publication, NENG2500, "Caterpillar Tools
and Shop Products Guide", for tools and supplies suitable
to collect and contain fluids in Caterpillar machines.
Dispose of all fluids according to local regulations and
NOTE: Perform the Charge Relief Valve - Test and Adjust
and the Main Relief Valve - Test and Adjust before
conducting the Pump Servo Neutral - Adjust.
(1) Servo. (2) Servo Ports. (3) Locknut. (4) Servo valve
neutral adjustment screw. (5) Main relief valve test ports.
Make sure that the parking brake is applied. Make sure
that the propel control lever is in neutral.
Disconnect the electrical connection for the vibratory
Remove the plugs from servo ports (2). Install the 3J-
7354 O-Ring Seals on the 6V-8628 Elbows. Install the
elbows in servo ports (2), and install the 4J-5477 O-
Ring Seals in the elbows.
Fabricate a hose assembly by using the 9X-2348 Hose
and 9X-3757 Coupling. Connect the hose assembly
between the elbows that were installed in the servo
Install the two 6V-7830 Tetragauges on the main relief
valve test ports (5).
Start and run the engine at high idle.
Tetragauges. The pressure readings should be
If the pressure readings are not identical, loosen locknut
(3) so that the neutral position of the servo piston may
be adjusted. Use an allen wrench in order to turn servo
valve neutral adjustment screw (4). Turn the screw
clockwise or counterclockwise in order to adjust the
mechanical center of the servo valve. The pressures on
the two 6V-7830 Tetragauges should change. Turn
servo valve neutral adjustment screw (4) until the
pressure readings on main relief valve test ports are
identical. Tighten locknut (3).
Remove the hose assembly and the elbows that
connect servo ports (2), and install the two plugs.