Oshkosh JLG 1500SJ, Service And Maintenance Manual

Page: 64 / 706

SECTION 3 - CHASSIS & TURNTABLE
3-14 – JLG Lift – 3121262
3.9 OSCILLATING AXLE SYSTEM
The oscillating front axle is attached to the frame by a pivot
pin, which allows all four wheels to remain on the ground
when traveling on rough terrain. The oscillating axle also
incorporates two lockout cylinders connected between the
frame and the axle. The lockout cylinders permit axle oscilla-
tion when the boom is in the transport position and drive is
commanded. The lockout cylinders will lock and hold the axle
when drive is not commanded or when the boom is outside
the transport position. The cylinders unlock when pilot pres-
sure is applied to the holding valves mounted on the cylinders
and lock when pilot pressure is removed. Pilot pressure is avail-
able from brake pressure and is controlled by a solenoid oper-
ated NC lockout valve mounted in the frame. To ensure the
lockout valve is functioning correctly, a NO pressure switch is
mounted between the lockout valve and the holding valves.
The system is “healthy” when pressure trips the pressure
switch when the lockout valve is commanded to be open and
conversely is healthy when the lack of pressure resets the pres-
sure switch when the lockout valve is commanded to be
closed. Failures in the oscillating axle system will cause the
control system to disallow lift up and telescope out when the
boom is within the transport position and will disallow drive/
steer, lift up and telescope out when the boom is beyond the
transport position.
NOTE: For more detailed information concerning system adjust-
ment and operation, refer to Section 6 - JLG Control Sys-
tem.
3.10 OSCILLATING AXLE BLEEDING PROCEDURE AND
LOCKOUT TEST
Lockout Cylinder Bleeding
To start the test, the axle must be fully oscillated in one direc-
tion. Start with oscillating the axle so that the left lock-out cyl-
inder is fully retracted (left front tire up), and the right lock-out
cylinder Is fully extended (right front tire down).
ENSURE PLATFORM IS FULLY LOWERED AND BOOM IS CENTERED OVER REAR
AXLE PRIOR TO BEGINNING BLEEDING PROCEDURE. MAKING SURE MACHINE
IS ON A LEVEL SURFACE AND REAR WHEELS ARE BLOCKED, BRAKE WIRE IS
DISCONNECTED.
1. Making sure machine is on a level surface and rear
wheels are blocked, machine is in transport mode.
2. Disengage the drive hubs.
3. Use suitable container to catch any residual hydraulic
fluid, place container under the lockout cylinder.
4. With the left lock-out cylinder retracted, open the
bleeder on top of the cylinder, then have an operator
from the platform (on high engine) feather drive. Acti-
vate drive fully.
5. Close the bleeder when there is a steady stream of oil
and not air.
6. With the axle in the same position, go to the right lock-
out cylinder and open the bleeder at the rod end. Acti-
vate drive in the same manner and close when all air has
been purged.
7. Close the bleeder when there is a steady stream of oil
and not air.
8. Oscillate the axle the other direction, left lock-out cylin-
der extended (tire down), right lock-out cylinder
retracted (tire up). Use the same procedure for the
bleeder in the rod end of the left lock-out cylinder, Then
the piston end of the right lock-out cylinder then close.
9. Repeat this process one more time to ensure that all air
has been purged from the system.
10. Perform oscillating axle lockout test.
11. If necessary, repeat steps 1 thru 9.
NOTE: Bleeding of the oscillating axles is an infrequent operation
performed after hydraulic line failure and or lock-out cylin-
der repair.