JLG 680S, Service And Maintenance Manual

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SECTION 5 - BASIC HYDRAULICS INFORMATION & SCHEMATICS
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Swashplate Inspection
• The finish on the piston shoe surfaces of the swash plate
should show no signs of scoring.
• Inspect swashplate bushing surface for wear and surface
for coating transfer from bushing.
1. To remove servo piston assembly from housing, start
with the four each capscrews and washers retaining
each cover plate.
2. In removing the cover plate from the servo piston bolt,
remove jam nut, washer, and seal washer. Hold the servo
piston bolt with hex key and unscrew cover plate off of
bolt.
3. Remove servo piston assembly and seal sub-assemblies
(two sets) from housing.
NOTE: Disassembly of servo piston assembly is not required.
4. Remove retaining ring from the front of housing. Press
the shaft, shaft seal or spacer, and washer from housing.
Remove retaining ring, thrust washer, thrust bearing,
second thrust washer, and second retaining ring from
shaft.
Housing Inspection
• Check the bearing (press fit) in housing. If needles remain
in cage, move freely, and setting at the dimension shown in
Figure 5-91., removal not required.
1. To remove cradle sub-assembly, remove the two cap-
screws retaining cradle inside housing. Removing cradle
subassembly from housing.
2. Remove button head capscrews (2 Qty.) to remove
bushing from cradle.
Bushing Inspection
• Inspect bushing for contamination embedment within
coating of bushing surface coming in contact with swash-
plate.
1. Remove all plugs from housing.
2. Discard the shaft seal, gaskets, and o-rings from all
assemblies. Replace with new seals upon reassembly.
ASSEMBLY
1. All parts should be cleaned and critical moving parts
lubricated before reassembly.
2. If necessary, press new bearing in housing to dimension
shown in Figure 5-91., with the numbered end of bear-
ing outward.
3. Install the two new seal sub-assemblies into the servo
piston cavity of housing.
4. Screw the cover plate onto the servo piston assembly.
Install new cover plate gasket in place on housing.
Install servo piston assembly and cover plate into servo
piston bore in right side of housing (as shown in
Figure
5-92. Retain cover plate with four each washers and cap-
screws. Torque capscrews 40 to 48 in.lbs (4.5 to 5.4 Nm).
To obtain neutral, centering the servo piston assembly is
required. Measure in from the left side and set servo pis-
ton 0.5 in. (12.7 mm) from surface of housing servo bore
as shown in Figure 5-92.
NOTE: Re-adjustment may be required for neutral at unit start-up.
5. Install new seal washer, washer, and jam nut to servo
piston bolt. Holding servo piston bolt with hex key
wrench Torque jam nut (150 to 160 in.lbs) 17 to 18 Nm.
Check the centering of servo piston assembly. Install
new cover plate gasket and cover plate to left side of
servo piston and retain with four each washers and #10-
24 capscrews. Torque capscrews 40 to 48 in.lbs (4.5 to
5.4 Nm).
Flange End of Housing
Numbered End
1.78 mm
(0.07 in.)
Figure 5-91. Housing Inspection
Left Side
Right Side
12.7 mm
(0.5 in.)
Adjust to centre piston
Install servo piston
in this direction.
Front Flange- Drive shaft End of pump
Figure 5-92. Servo Piston Installation