JLG 450A_AJ Series II Service Manual - Manual (Page 60)

SECTION 3 - CHASSIS & TURNTABLE
3-20 – JLG Lift – 3121290
3.3 RE-ALIGN TORQUE HUB INPUT COUPLING
This procedure applies to torque hubs with integral brakes:
Equipment Required
1. Hydraulic power supply (hand pump) capable of pro-
ducing 200 psi (13.8 bar).
2. Hydraulic fittings to adapt hydraulic supply to brake
release port on hub.
Procedure
1. Using appropriate fittings, connect a line from hydraulic
power supply to brake port.
2. Pressurize brake release port to 155 - 200 psi (10.6 -
13.8 bar) to release brake.
3. Verify brake is released by rotating input coupling or
hub spindle. Once brake is released, input coupling is
free to re-align with drive motor.
4. Install drive motor on hub. Release hydraulic pressure at
brake release port. Coupling remains in position.
5. Disconnect hydraulic power supply and reconnect line
to brake release port.
3.4 DRIVE MOTOR
NOTE: This procedure covers:
2WD motors used on GM powered machines.
2WD motors used on Caterpillar and Deutz powered
machines.
All 4WD motors.
Description
Drive motors are low to medium power, two-position axial pis-
ton motors incorporating an integral servo piston. They are
designed for operation in open and closed circuit applications.
The standard control is a direct acting single line hydraulic
control. The integral servo piston controls motor displace-
ment.
Motors are spring biased to maximum displacement and
hydraulically shifted to minimum displacement. Minimum and
maximum displacement can be set with fixed internal stops.
The large diameter servo piston allows smooth acceleration
and deceleration with relatively large circuit orificing.
Figure 3-6. Drive Motor Cross Section
Bias spring
Servo piston
Swashplate
Output
Shaft
Piston
Slipper
Cylinder
Block
Endcap
Shaft
Seal
Bearing
Minimum
Angle
Stop
Valve plate