SkyTrak 6036 Service Manual - Manual (Page 177)

Section 9 Hydraulic System
Model 6036/6036T S/N 9B0500 thru 14833 9-27
Park Lock Release Valve and
Transmission De-Clutch Valve
When the park lock switch on the instrument panel
is placed in the engaged (up) position, the park
lock release valve solenoid is de-energized and the
valve spool is spring positioned so that hydraulic
flow from the park lock piston is directed through
ports A to C in the park lock release valve, Fig.
9.15. With no pressure on the park lock piston, the
park lock springs force the discs together, this
engages the park lock. With the park lock release
valve solenoid in the de-energized position,
pressurized hydraulic oil flows through the park lock
release valve through ports D to B, Fig. 9.15. The
transmission de-clutch valve spool is shifted so it is
piloted open allowing pressurized hydraulic oil to
reduce internal control pressure inside the transmis-
sion. The reduced internal control pressure in the
transmission does not allow engagement of the
transmission clutch packs, eliminating transmission
drive power to the drive axles. The park lock light
on the dash will illuminate whenever the park lock is
engaged and the ignition switch is in the RUN
position.
When the park lock switch on the instrument panel
is placed in the disengaged (down) position, the
park lock release valve solenoid is energized and
the valve spool is positioned so that the hydraulic
flow is directed through ports D to A in the park lock
release valve, Fig. 9.15 to the park lock. With
hydraulic pressure being applied to the park lock
piston, the park lock springs are compressed.
Which disengages the park lock discs. With the
park lock release valve solenoid energized, the
transmission de-clutch valve spool is spring-
positioned so that hydraulic oil that was used to de-
clutch the transmission can return to the reservoir
through ports B to C in the park lock release valve,
Fig. 9.15. This permits internal control pressure in
the transmission to return to normal, which will
allow engagement of the transmission clutch packs
when the transmission is shifted in gear.
IMPORTANT: Never engage the park lock while
the machine is in motion. The park lock is not
designed to be used as a means to slow or stop
machine travel and could be damaged as a result.
b. Pressure Checks and Adjustments
Sequence Valve
1. Engage the park lock, place the travel select
lever in neutral, and stop the engine.
2. Operate the hydraulic controls after the engine
has stopped to relieve any trapped pressure.
Warning
Relieve hydraulic pressure before servicing any
hydraulic component. Escaping hydraulic fluid
under pressure can penetrate the skin causing
serious injury.
Warning
Wait for the hydraulic fluid to cool before serv-
icing any hydraulic component. Hot hydraulic
fluid can cause severe burns.
Before starting the engine be sure all hydraulic
connections are tight and all tools are removed
from the forklift.
Warning
Warning
Relieve hydraulic pressure before servicing any
hydraulic component. Escaping hydraulic fluid
under pressure can penetrate the skin causing
serious injury.
3. Remove the transmission cover from the
frame.
4. Install a tee and pressure gauge capable of
measuring 0-4000 psi (0-275,6 bar) in the 15
gpm section outlet of the tandem pump, Fig.
9.15.
5. Start the engine and allow it to run at idle.
6. Check the pressure gauge reading at the
tandem pump.
7. Pressure gauge reading should read between
610 - 660 psi (42 - 45,5 bar). If not, adjust the
sequence valve, turning the adjustment screw
clockwise to increase pressure or counterclock-
wise to decrease pressure.
8. Stop the engine. Operate the hydraulic controls
after the engine has stopped to relieve any
trapped pressure.
9. Remove the pressure gauge and tee from the
tandem pump and reconnect the hydraulic line.
10. Install the transmission cover after adjustment.
Pressure Reducing Valve
1. Engage the park lock, place the travel select
lever in neutral, and stop the engine.