JLG 740A, Service And Maintenance Manual

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SECTION 5 - HYDRAULICS
5-6 – JLG Lift – 3121160
9. Using suitable protection, clamp the cylinder rod in
a vise or similar holding fixture as close to the piston
as possible.
NOTE: Step 10 applies only to the steer cylinders.
10. Loosen and remove nut which attaches the piston to
the rod, and remove the piston.
11. Loosen and remove the cap screw(s), if applicable,
which attach the tapered bushing to the piston.
12. Insert the cap screw(s) in the threaded holes in the
outer piece of the tapered bushing. Progressively
tighten the cap screw(s) until the bushing is loose
on the piston.
13. Remove the bushing from the piston.
14. Screw the piston counter clockwise (CCW), by
hand, and remove the piston from cylinder rod.
15. Remove and discard the piston o-rings, seal rings,
and backup rings.
16. Remove piston spacer, if applicable, from the rod.
17. Remove the rod from the holding fixture. Remove
the cylinder head gland and retainer plate, if applica-
ble. Discard the o-rings, back-up rings, rod seals,
and wiper seals.
Cleaning and Inspection
1. Clean all parts thoroughly in an approved cleaning
solvent.
2. Inspect the cylinder rod for scoring, tapering, ovality,
or other damage. If necessary, dress rod with
Scotch Brite or equivalent. Replace rod if necessary.
3. Inspect threaded portion of rod for excessive dam-
age. Dress threads as necessary.
4. Inspect inner surface of cylinder barrel tube for scor-
ing or other damage. Check inside diameter for
tapering or ovality. Replace if necessary.
5. Inspect threaded portion of barrel for damage. Dress
threads as necessary.
6. Inspect piston surface for damage and scoring and
for distortion. Dress piston surface or replace piston
as necessary.
7. Inspect threaded portion of piston for damage.
Dress threads as necessary.
8. Inspect seal and o-ring grooves in piston for burrs
and sharp edges. Dress applicable surfaces as nec-
essary.
9. Inspect cylinder head inside diameter for scoring or
other damage and for ovality and tapering. Replace
as necessary.
10. Inspect threaded portion of head for damage. Dress
threads as necessary.
11. Inspect seal and o-ring grooves in head for burrs
and sharp edges. Dress applicable surfaces as nec-
essary.
12. Inspect cylinder head outside diameter for scoring
or other damage and ovality and tapering. Replace
as necessary.
13. If applicable, inspect rod and barrel bearings for
signs of correct excessive wear or damage. Replace
as necessary.
a. Thoroughly clean hole, (steel bushing) of burrs,
dirt etc. to facilitate bearing installation.
b. Inspect steel bushing for wear or other damage.
If steel bushing is worn or damaged, rod/barrel
must be replaced.
c. Lubricate inside of steel bushing with WD40
prior to bearing installation.
d. Using an arbor of the correct size, carefully
press the bearing into steel bushing.
Figure 5-3. Cylinder Rod Support
Figure 5-4. Tapered Bushing Removal