JLG sky trak mmv Service Manual page 444

Hydraulic System
5
4. Install both precision wearbands (17) and the
capped T-seal (18) onto the piston (8).
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.
5. Install the head gland (7) and piston (8) onto the
rod (4).
IMPORTANT: Protect the finish on the rod at all times.
Damage to the surface of the rod can cause seal failure.
6. Fasten the rod end 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. Apply
Loctite #271 (red) and install the locknut (9) onto the
rod (4). Torque the nut to 2600-2900 lb/ft (3526-3932
Nm). The threads will deform upon tightening,
locking the nut in place.
IMPORTANT: Avoid using excess force when clamping
the cylinder in a vise. Apply only enough force to hold the
cylinder securely. Excessive force can damage the cylinder.
7. Place the attachment tilt cylinder tube (2) in a soft-
jawed vise or other acceptable holding equipment if
possible.
IMPORTANT: When sliding the rod and piston assembly
in the tube, prevent the threaded end of the tube from
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2
9
8
18
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23
17
19
14
15
10
11
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damaging the piston ( 8 ). Keep the rod centered within
the tube to help prevent binding.
8. Carefully insert the rod (4) with all attachments
straight into the tube (2).
9. Using a pin spanner wrench, thread the head gland
(7) almost completely into the tube (2), leaving just
enough room to install a new locking insert (13) into
its hole in the head gland threads.
10. Install a new locking insert (13). Thread the head
gland (7) tightly into the tube and torque to 300-400
lb/ft (407-542 Nm).
11. Using new oiled o-rings, thread the 4000 psi (276 bar)
counterbalance valve (5) and the pilot-operated
check valve (6) into the attachment tilt cylinder.
Torque to 30-35 lb/ft (41-47 Nm).
12. If necessary, install a grease fitting (3) into the
tapped hole in the end of the rod (4). Lubricate the
bushings in the rod end through the grease fitting
with multi-purpose grease before the vehicle is
operated.
1
12
13
7
16
4
3
20
Model MMV Rev. 12/04
20
MT1860