Swashplate Neutral Adjustment Procedure
(9XL1-228, 3WZ1-157, 2JM1-578, 4JZ1-121, 3TM1-705,
5BZ1-118, 6EN1-126, 1ZN1-120, 2TN1-117)
Tests should be performed on tires or loose dirt.
Tires are recommended. Never operate the
vibratory system when the machine is on
Make sure the parking brake is applied, and the
propel control lever is in neutral.
(1) Test port for vibratory (low amplitude) pressure. (2) Test port for
vibratory (high amplitude) pressure. (3) Servo Port.
Connect two 60 000 kPa (8700 psi) pressure gauges to
test ports (1) and (2).
Install a 3445 kPa (500 psi) minimum pressure hose
and needle valve between servo port (3) and the
opposite servo port, on other side. This will cross port
the servo and remove the effects of any control
pressure on the servo piston.
Start and slowly accelerate the engine to full throttle.
Operate the vibratory system in both high and low
amplitudes several times and then stop the vibratory
With the servo cross-port line installed and the needle
valve open, note the system pressure gauge readings
with engine running at low idle. The difference in the
system pressure gauge readings is the offset pressure.
To achieve finer gauge resolution, lower pressure
gauges will be required. 60 000 kPa (8700 psi)
pressure gauges are used at the beginning to
prevent gauge damage.
If the offset pressure is not zero, loosen the servo
locknut with an 11/16 hex wrench. Turn the adjustment
screw with a 3/16 internal hex wrench to decrease the
highest system pressure to half of the offset pressure.
Close the needle valve (disconnect the servo cross port
line/plug the servo ports). Operate the vibratory system
in both high and low amplitudes several times. Return
the pump to neutral (non-vibratory) and open the needle
valve (reinstall the cross-port line) this will allow the
servo spring to locate the swashplate in the neutral
Install the low pressure gauges and note the system
pressure gauge readings. If the offset pressure is not
zero, repeat Steps 5 through 8.
Once the swashplate neutral has been found, hold the
servo adjustment screw from turning and torque the
servo locknut to 18 to 24 Nm (13 to 18 lb-ft).
Stop the engine. Remove the pressure gauges.