JLG 450A_AJ Series II Service Manual - Manual (Page 68)

SECTION 3 - CHASSIS & TURNTABLE
3-28 – JLG Lift – 3121290
VALVE PLATE
Valve plate condition is critical to motor efficiency. Inspect
valve plate surfaces for excessive wear, grooves, or scratches.
Replace or resurface grooved or scratched valve plates. Mea-
sure valve plate thickness and replace if worn beyond mini-
mum specification.
Valve plate can be resurfaced if finished thickness is not below
minimum specification shown in drawing.
SWASHPLATE AND JOURNAL BEARINGS
Inspect running face, servo ball-joint, and swashplate journal
surfaces for damage or excessive wear.
Some material transfer may appear on these surfaces and is
acceptable providing surface condition meets specifications
shown.
Measure swashplate thickness from journals to running face.
Replace swashplate if damaged or worn beyond minimum
specification.
Inspect journal bearings for damage or excessive wear.
Replace journal bearings if scratched, warped, or excessively
worn. Polymer wear layer must be smooth and intact.
SHAFT BEARINGS
Inspect bearings for excessive wear or contamination. Rotate
bearings while feeling for uneven movement. Bearings should
spin smoothly and freely. Replace bearings that appear worn
or do not rotate smoothly.
SHAFT
Inspect motor shaft. Look for damage or excessive wear on
output and block splines. Inspect bearing surfaces and sealing
surface. Replace shafts with damaged or excessively worn
splines, bearing surfaces, or sealing surfaces.
SERVO PISTON AND MINIMUM ANGLE STOP
Inspect minimum angle stop, servo piston head, and servo pis-
ton ball-socket for damage or excessive wear. Replace as needed.
LOOP FLUSHING SPOOL
Inspect loop flushing spool. Check for cracks or damage.
Replace as needed.
3.83 mm [0.151 in] min.
0.025 mm
[0.001 in]
0.0076 mm
[0.00030 in]
convex max
LV
25.8 mm
[1.015 in]
24.6 mm
[0.969 in]
KV
Thickness equality
side to side:
0.05 mm [0.002 in]
0.0025 mm
[0.0001 in]