Steer Select Valve (Three-Mode Steer) - JLG sky trak mmv Service Manual

Hydraulic System
9.12.9

Steer Select Valve (Three-Mode Steer)

With the three-mode steer, the vehicle can be used in the
front-wheel, four-wheel or crab steering mode. The steer
select valve (1) controls the direction of hydraulic fluid
flow to the steering cylinders mounted on each axle. The
steer select valve (1) is attached to a manifold (2)
mounted on the hydraulic reservoir/engine mount (3).
1
3
2
The steer select valve (4) contains two solenoids (5) that
direct the flow of hydraulic fluid according to steering in-
put. The valve is a direct dual-solenoid operated, spool-
type main control valve.
The valve consists of a housing (4), two solenoids (5), a
control spool (6) and two return springs (7). In the de-en-
ergized state, the spool (6) is held by the return springs
(7) in the center position.
The spool is shifted via the action of the two wet-pin type
solenoids (5). The force of an acting solenoid pushes
against the push pin (8) on the end of the spool (6). The
spool is shifted from its normal position to the end position
for selected flow.
When the solenoid is de-energized, the control spool (6)
is returned to its normal condition by the centering
springs (7).
9.126
8
MT3420
Verify the correct operation of the steer select valve sole-
noids before considering replacement of the valve. Refer
to Section 10.7, Electrical System Troubleshooting and
Section 10.13.14, Steer Select Valve . The housing (4) of
the steer select valve is not serviceable and must be re-
placed if defective.
a. Steer Select Manifold and Valve Removal
1. Park the vehicle on a firm, level surface, fully retract
all hydraulic cylinders, ground the attachment (if
any), place the travel select lever in [N] NEUTRAL,
place the neutral lock lever in the [N] NEUTRAL
LOCK position, engage the park brake switch and
shut the engine OFF.
2. Place an Accident Prevention Tag on both the
ignition switch and the steering wheel, stating that
the vehicle should not be operated. Refer to Section
1.5, Accident Prevention Tag Usage .
5
4
5
4 6
7 7
Model MMV Rev. 12/04
8
MT1480