JLG 4017PS Service Manual - Manual (Page 151)

8-19 3706PS, 3707PS, 4014PS, 4017PS, 33.7, 37.6, 37.7
Hydraulic System
8.10.7 Steer Select Valve
The machine can be used in the front-wheel, four-wheel
or crab steering mode. The steer select valve (4) controls
the direction of hydraulic fluid flow to the steering cylinder
mounted on each axle. The steer select valve is attached
inside the frame near the front axle.
Verify the correct operation of the steer select valve
solenoids before considering replacement of the valve.
Refer to Section 9.8, “Electrical System Schematics.” The
housing of the steer select valve is not serviceable and
must be replaced if defective.
a. Steer Select Manifold and Valve Removal
1. Park the machine on a firm, level surface, level the
machine, fully retract the boom, lower the boom,
place the transmission control lever in (N) NEUTRAL,
engage the park brake and shut the engine OFF.
2. Place a Do Not Operate Tag on both the ignition key
switch and the steering wheel.
3. Open the engine cover. Allow the system fluids to
cool.
4. Properly disconnect the battery.
5. Label, disconnect and cap the hydraulic hoses and
the electrical plugs connected to the steering select
valve.
6. Remove the bolts holding the steer select valve to
the mounting plate on the frame.
7. Remove the steer select valve from the machine.
Wipe up any hydraulic fluid spillage in, on, near and
around the machine.
b. Steer Select Manifold and Valve Disassembly,
Cleaning, Inspection and Assembly
1. Place the steer select assembly on a suitable work
surface.
2. Separate the steer select solenoids from the spool.
Discard the o-rings.
3. Clean all components with a suitable cleaner before
inspection.
4. Inspect the solenoid cartridges for proper operation.
Check by shifting the spool to ensure that it is
functioning properly. Check that the spring is intact.
Inspect the cartridge interior for contamination.
5. Inspect internal passageways of the steer select
valve for wear, damage, etc. If inner surfaces of the
manifold DO NOT display an ultra-smooth, polished
finish, or components are damaged in any way,
replace the manifold or appropriate part. Often, dirty
hydraulic fluid causes failure of internal seals and
damage to the polished surfaces within the
secondary function manifold.
Note: ALWAYS replace seals, o-rings, gaskets, etc.,
with new parts to help ensure proper sealing and
operation. Lubricate seals and o-rings with clean
hydraulic oil.
6. Install the solenoids in the steer select housing.
c. Steer Select Valve and Manifold Installation
1. Install the steer select valve to the mounting plate
under the left front side of the frame using the two
bolts.
2. Connect all the hydraulic hoses, fittings, solenoid
wire terminal leads, etc., to the steer select valve
3. Check the routing of all hoses, wiring and tubing for
sharp bends or interference with any rotating
members, and install tie wraps and/or protective
conduit as required. Tighten all hose clamps.
4. Properly connect the battery.
5. Start the engine and run at approximately 1/3-1/2
throttle for about one minute without moving the
machine or operating any hydraulic functions.
6. Inspect for leaks and check the level of the hydraulic
fluid in the reservoir. Shut the engine OFF.
Note: Check for leaks and repair as required before
continuing. Add hydraulic fluid to the reservoir as
needed.
7. Wipe up any hydraulic fluid spillage in, on, near and
around the machine, work area and tools.
8. Close and secure the engine cover.
9. Remove the Do Not Operate Tag from the ignition
key switch and the steering wheel.
MAM0300
4
3706PS FRAME SHOWN