JLG sky trak mmv Service Manual page 407

f. Main Control Valve Assembly
This section covers the assembly of the end cap (1), at-
tachment tilt (2) and frame sway (3) sections of the main
control valve.
Note: ALWAYS replace seals, o-rings, gaskets, etc.,
with new parts to help ensure proper sealing and opera-
tion. Lubricate seals and o-rings with clean hydraulic oil.
Assemble the End Cap Section
1. Install a new oiled o-ring (4) and the plug (5) into the
end cap section (1).
Assemble the Frame Sway Section
1. Assemble the end mechanism (11) by inserting a
new small oiled o-ring (12) onto the spool end (13).
Insert the spool end, the spring seat (14), the spring
(15), the other spring seat (14), a new large oiled o-
ring (16) and the spool cap retainer (17) into the
spool cap (18) and then into the retainer (19).
2. Insert a new oiled o-ring (20) into the section and
attach this end mechanism (11) with the capscrews
(21).
3. Assemble the other end mechanism (6) by inserting
the spool cap (7) into the retainer (8).
4. Insert a new oiled o-ring (9) onto the section and
attach the end mechanism (6) with the
capscrews (10).
5. Insert the shuttle (22), poppet (23) and spring (24)
into the section (3).
6. Place a new oiled o-ring (25) between the mid inlet
section (26) and the frame sway section (3) and slide
the frame sway section onto the tie rods.
Place a new oiled o-ring (27) on the frame sway section
(3).
Assemble the Attachment Tilt Section
1. Assemble the end mechanism (11) by inserting a
new small oiled o-ring (12) onto the spool end (13).
Insert the spool end, the spring seat (14), the spring
(15), the other spring seat (14), a new large oiled o-
ring (16) and the spool cap retainer (17) into the
spool cap (18) and then into the retainer (19).
2. Insert a new oiled o-ring (20) into the section and
attach this end mechanism (11) with the
capscrews (21).
3. Assemble the other end mechanism (6) by inserting
the spool cap (7) into the retainer (8).
Model MMV Rev. 12/04
4. Insert a new oiled o-ring (9) onto the section and
attach the end mechanism (6) with the
capscrews (10).
5. Install the relief valves (28) and new oiled o-ring (29)
after assembling them using the procedure that
follows.
6. Insert the poppet (30) and spring (31) into the
section (2).
7. Place a new oiled o-ring (32) between the
attachment tilt section (2) and the end cap (1)
section.
8. Slide the attachment tilt section (2) onto the tie rods
(33 & 34).
9. Slide the end cap (1) onto the tie rods (33 & 34).
10. Assemble the upper tie rod nut (35) and the two lower
tie rod nuts (36). Torque two lower tie rod nuts (36) to
13-15 (18-20 Nm) and the third upper tie rod nut (35)
to 30-36 lb/ft (41-49 Nm).
Assemble the Relief Valves (Attachment Tilt Section).
Note: There is a seal and spring kit package for assem-
bling the relief valves.
1. Install the relief valve poppets (37 and 38), new
back-up ring (39), new oiled o-ring (40), piston (41),
new small spring (42), new large spring (43), new
oiled o-ring (44), new back-up ring (45) and new
large oiled o-ring (46) into the relief valve body (47).
2. Install the pilot poppet (48) and new spring (49) into
the plug (50).
3. Install the plug (50) onto the body (47).
4. Install the adjustment screw (51) and new oiled o-
ring (52).
5. Tighten the nut (53) onto the body (47).
6. Check that the piston (41) moves freely inside the
relief valve assembly by pushing the piston in from
the threaded end (54) of the relief valve.
7. Install a new oiled o-ring (29) into the section.
8. Using a wrench on the body (47), install the relief
valve (28) onto the section.
Hydraulic System
9.109