JLG 660SJ Service Manual - Manual (Page 68)

SECTION 3 - CHASSIS & TURNTABLE
3-18 – JLG Lift – 3121202
3.3 FREE WHEELING OPTION
To Disengage Drive Motors and Brakes (Free
Wheel) for Towing, etc.
1. Chock wheels securely if not on flat level surface.
2. Disconnect both drive hubs by inverting disconnect
caps in center of hubs.
3. If equipped, move steer/tow selector valve to float
(tow) position by pulling valve knob out.
To Engage Drive Motors and Brakes (Normal
Operation)
1. If equipped, move steer/tow valve to steer position
by pushing valve knob in.
2. Connect both drive hubs by inverting disconnect
cap in center of hub.
3. Remove chocks from wheels as required.
3.4 DRIVE MOTOR (S/N 75606 TO PRESENT)
Description
The drive motors are low to medium power, two-position
axial piston motors incorporating an integral servo piston.
They are designed for operation in both open and closed
circuit applications. The standard control is a direct acting
single line hydraulic control. The integral servo piston con-
trols motor displacement.
The motors are spring biased to maximum displacement
and hydraulically shifted to minimum displacement. Mini-
mum 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.
DISCONNECT
CAP
DISCONNECT
CAP
(REVERSED)
DRIVE
HUB
DRIVE
HUB
Drive Hub Engaged
Drive Hub Disconnected
Figure 3-15. Disconnecting the Drive Hubs
Bias spring
Servo piston
Swashplate
Output
Shaft
Piston
Slipper
Cylinder
Block
Endcap
Shaft
Seal
Bearing
Minimum
Angle
Stop
Valve plate
Figure 3-16. Drive Motor Cross Section