SkyTrak 3606 Service Manual - Manual (Page 292)

Section 9
9-98
4. Attach a sling to the hoist/lower cylinder and to a
hoist or an overhead crane. Support the hoist/lower
cylinder in the sling, and remove both nuts,
capscrews and cylinder mount pins from the cylinder.
5. Safely and carefully, remove the hoist/lower cylinder
from the vehicle. Wipe up any hydraulic fluid spillage
in, on, near and around the vehicle.
b. Hoist/Lower Cylinder Disassembly
Note: An additional O-ring may be included at the base
of the cylinder rod. This additional O-ring may be
discarded, as it served only in a temporarily protective
role to keep paint off the rod while the cylinder was
painted at the factory.
1. Clean the hoist/lower cylinder (1, Fig. 9– 67) with a
suitable cleaner. Remove all dirt, debris and grease
from the cylinder.
2. Secure the hoist/lower cylinder in a soft-jawed vise or
other acceptable holding equipment if possible. DO
NOT damage the tube (3).
Note: Significant pressure may be trapped inside the
cylinder. Exercise caution when removing the counter-
balance valve (2) from the eyelet end of the tube (3).
3. Remove the counterbalance valve (2) from the eyelet
end of the tube (3).
IMPORTANT: DO NOT tamper with or attempt to reset
the counterbalance valve cartridge. If adjustment or
replacement is necessary, replace the counterbalance
valve with a new one.
4. If necessary, remove the grease fitting (19) from the
tapped hole in the end of the rod weldment (18).
5. If the self-align bearing (17) needs replacement,
support the rod (18) in a soft-jawed vise or other
suitable holding device. Carefully press the bearing
out of the rod eyelet.
6. Extend the rod weldment (18) as required to allow
access to the base of the cylinder.
7. Using a pin spanner wrench, unscrew the head gland
(14) from the tube (3). The gland was originally
torqued to 300-400 lb/ft (407-542 Nm), so a
considerable amount of force is required. Carefully
slide the gland down along the rod toward the eyelet
end, away from the cylinder tube (3).
IMPORTANT: Protect the finish on the rod at all times.
Damage to the surface of the rod can cause seal failure.
8. Carefully pull the rod (18) with all attachments
straight out of the tube (3).
IMPORTANT: When sliding the rod and piston assembly
in the tube, prevent the threaded end of the tube from
damaging the piston (6). Keep the rod centered within the
tube to help prevent binding.
9. Fasten the rear of the rod in a soft-jawed vise and put
a padded support below and near the threaded end
of the rod to help prevent damage to the rod.
10. Remove both locking inserts (15) from their
installation holes in the head gland threads. Pry or
drill out the inserts as required. DO NOT damage the
head gland threads. New locking inserts will be
required for reassembly.
11. Remove the 2.00-12 UN locknut (4) from the rod
weldment (18). The nut was installed with Loctite
#271 (red) and torqued to 1550-1750 lb/ft (2102-
2373 Nm).
Note: It may be necessary to apply heat to break the
bond of the sealant between 2.00-12 UN locknut (4) and
the rod (18) before the piston (6) can be removed. Some
parts of cylinders are sealed with a special organic seal-
ant and locking compound. Before attempting to disas-
semble these parts, remove any accessible seals from
the area of the bonded joint. Wipe off any hydraulic oil
and heat the joint uniformly to break the bond. A temper-
ature of 300° to 400° F (149° to 204° C) will destroy the
bond. Avoid overheating or the parts may become dis-
torted or damaged. Apply sufficient torque or pressure for
removal while the parts are still hot. Breakdown of seal-
ant will leave a white, powdery residue on threads and
parts. Clean the residue away with a soft brass wire
brush prior to reassembly, and wipe with Loctite “T”
cleaner before reinstallation.
12. Remove the piston (6) from the rod weldment (18).
13. Remove both precision wearbands (5) and the
capped T-seal (7) from the piston (6).
Note: The T-seal actually consists of four components; a
wide, flexible inner band, the flexible T-seal band itself,
and two supportive split caps that mount on either side of
the “T” itself.
14. Remove the O-ring (9), backup ring (10) and O-ring
(11) from the head gland (14). Slide the rings off over
the rod (18) and piston (6) to remove them from the
rod weldment (18).
15. From within the head gland (14), remove the
precision wearbands (12), the deep Z-seal with
backup (13), and, from the other end, remove the
sealed outside diameter heavy-duty rod wiper (16).
16. From within the piston (6), remove the small O-ring
(8).
Model 3606 • Origin 10/99