JLG sky trak mmv Service Manual page 452

Hydraulic System
22
19
17
16
10
26
25
3. Install one of the precision wearbands (19), the
buffer seal (26) with the angled edge toward the
outside of the cylinder, another precision wearband
(19), the deep Z-seal with rod back-up (20) and the
sealed outside diameter heavy-duty rod wiper (21)
into the head gland (6). Orient the Z-seal edge (24).
The rod wiper lip (23) should be toward the outer
end of the head gland and the seal lips toward the
inner end of the head gland. Use tools that will not
damage the seals.
4. Install new oiled o-ring (18), back-up ring (17) and
oiled o-ring (16) onto the head gland (6).
5. Fasten the trunnion end 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.
6. Carefully slide the head gland (6), then the rod
spacer (10) onto the rod (5).
Note: The holes (25) in the rod spacer ( 10 ) must be
near the piston (7).
7. Carefully slide the piston (7) onto the rod spacer (10)
and rod (5). Apply Loctite Threadlocker #243 to the
piston and torque the piston to 350-450 lb/ft
(475-610 Nm).
9.154
1
6
8
18
21
20
24
5
8
23
2
8. Turn the rod spacer (10) as required to align the
piston setscrew hole. The setscrew is used to
provide a secondary lock on the piston. Apply Loctite
Threadlocker #243 to the setscrew (9) and thread it
into the piston (7). Torque the setscrew to 13-15 lb/ft
(155-175 lb/in) (18-20 Nm).
9. Install new locking inserts (8) into the holes in the
head gland threads.
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.
10. Secure the extend/retract cylinder tube (2) in a soft-
jawed vise or other acceptable holding equipment if
possible.
11. Lubricate the inside of the tube (2) and outside of the
piston (7) and head gland (6) with clean, filtered
hydraulic oil.
12. Apply a compression sleeve or other suitable tool to
the head gland (6) and piston (7) in order to
compress the o-rings, back-up rings and seals while
inserting the assembled piston, rod and head into
the tube (2).
3
4
11
9
14
15
14
7
Model MMV Rev. 12/04
13
12
MM4740