Drive Motor; Description; Shaft Seal Replacement - JLG 800A Service And Maintenance Manual

SECTION 3 - CHASSIS & TURNTABLE
3.6

DRIVE MOTOR

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 appli-
cations. The standard control is a direct acting single line
hydraulic control. The integral servo piston controls motor dis-
placement.
The 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.
Bias spring
Minimum
Angle
Stop
Cylinder
Block
Piston
Endcap
Valve plate
Figure 3-7. Drive Motor Cross Section
3-18
Servo piston
Swashplate
Output
Shaft
Shaft
Seal
Bearing
Slipper

Shaft Seal Replacement

REMOVAL
1. Remove the snap ring (1) retaining the shaft seal and
support washer.
1
2
3
1. Snap Ring
2. Support Washer
3. Shaft Seal
Figure 3-8. Removing the Shaft Seal
2. Remove the support washer (2).
3. Carefully pry out the shaft seal (3).
To avoid damaging the shaft during removal, install a
large sheet metal screw into the chuck of a slide ham-
mer. Drive the screw into the seal surface and use the
slide hammer to pull the seal.
4. Discard the seal.
INSPECT THE COMPONENTS
Inspect the new seal, the motor housing seal bore, and the
sealing area on the shaft for rust, wear, and contamination.
Polish the shaft and clean the housing if necessary.
INSTALLATION
1. Cover the shaft splines with an installation sleeve to pro-
tect the shaft seal during installation.
2. Install a new shaft seal with the cupped side facing the
motor. Press seal into housing until it bottoms out. Press
evenly to avoid binding and damaging the seal.
3. Install seal support washer.
4. Install snap ring.
5. Remove the installation sleeve.
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