JLG 534D-10 - Manual (Page 108)

Hydrostatic Drive Pump
6.10 534D-9, 534D-10 & 544D
6.6.9 Drive Pump Pressure
Drive pump pressure determines the drive power of the
machine. Low drive pressure will result in less power.
Install a digital or high pressure gauge (10,000 psi -
689 bar), hose and adapter on the MA port (7). Apply the
park brake and put the 2WD/4WD switch in the 2WD
position. Move the shift lever to the forward position and
run the engine at full throttle. The gauge reading should
be 6,300 psi (434 bar). Adjust the POR relief valve (8)
located on top of the pump as necessary. To adjust this
relief valve, loosen the lock-nut and turn the adjusting
screw clockwise to increase pressure and
counterclockwise to decrease pressure. Move the gauge
to the MB port (9) of the drive pump to repeat the
procedure with the shift lever in the reverse position.
There are also high pressure/anti-cavitation relief valves
on the drive pump. These could influence drive system
pressure with a low setting or missing o-ring. On
machines with 6,300 psi (434 bar) drive pressure, adjust
these valves to 6,800 psi (469 bar) drive pressure.
Normally, these high pressure relief valves do not require
checking. However, if there is a drive power problem and
adjustment of the POR relief valve on the main pump
does not change the pressure, these valves may have to
be adjusted. Install a digital or high pressure gauge
(10,000 psi - 689 bar), hose and adapter on the MA port
on the pump. To check these high pressure relief valves,
raise the setting on the POR valve on the drive pump.
Loosen the lock-nut on the POR valve and turn the
adjusting screw clockwise one turn to increase pressure.
With the gauge on the MA port, set the park brake, move
the shift lever to the forward position and run the engine
at full throttle. Adjust the forward high pressure relief (10)
to 6,800 psi (469 bar). Move the gauge to the MB port of
the drive pump to repeat the procedure with the shift lever
in the reverse position. Adjust the reverse high pressure
relief (11) to 6,800 psi (469 bar). Leave the gauge and
adapter in the MB port. Reset the POR valve back to the
original setting. With the park brake on, put the shifter in
reverse and run the engine at full throttle. The pressure
should be 6,300 psi (434 bar). Adjust the POR valve as
required.
The traction lock valve also has two high-pressure/anti-
cavitation relief valves. Normally, these require no
adjustment. However, they can adversely affect drive
system pressure if, say, they are set to low, or an o-ring
is missing. To check these valves, raise the POR valve
setting above 6,800 psi (469 bar). Set the forward high
pressure relief valve (12) on the pump to 6,800 psi
(469 bar). Then lower the forward high pressure relief
valve on the traction lock valve under 6,800 psi (469 bar).
Turn the valve in 1/8 turn and secure the lock-nut. Repeat
the procedure for reverse (13). Then reset the POR valve
to 6,300 psi (434 bar).
6.6.10 Machine Operation
Complete the following checks to ensure that the traction
lock valve, 2WD/4WD solenoid valve and the begin point
on the front drive motor are operating correctly.
With the machine at operating temperature, drive the
machine in a flat, smooth open area. Set the machine for
4WD operation. Depress the traction lock switch. Drive
the machine at full speed. Release the traction lock
switch; the machine should pick up speed. Shift the
machine to 2WD and repeat this test. The machine
should speed again. If maximum speeds are in question,
check machine speed. Run the machine in 2WD and
4WD in forward and reverse at maximum RPM for one
minute. In 2WD, the machine will travel 100 feet (30,5 m)
in 3.6 - 4.0 seconds. In 4WD, the machine will travel
100 feet (30,5 m) in 10.6 - 11.6 seconds. The machine
must be traveling at full speed at the start of the
measured distance.
MX0890
R
X 1
X 2
P S
T 1
F A
T 2
P S
G
M A
M B
Top View
Left Side View
7
8
9
11
10
"M
2
" "M
1
"
MX0900
"B" "A"
13 12