JLG sky trak mmv Service Manual page 477

c. Fork Side Shift Cylinder Internal Cleaning
1. Remove all hydraulic fluid, dirt and debris from the
inner surface of the cylinder.
2. Discard all seals, back-up rings and o-rings. Replace
with new items from a complete seal kit to help
ensure proper cylinder function.
3. Clean all metal parts with an approved cleaning
solvent such as trichlorethylene. Carefully clean
cavities, grooves, threads, etc.
d. Fork Side Shift Cylinder Inspection and Repair
1. Inspect all parts for wear and damage. If inner
surfaces of the cylinder (1) do not display an ultra-
smooth, polished finish, or are damaged in any way,
replace the damaged part. Often, dirty hydraulic fluid
causes failure of internal seals and damage to the
polished surfaces within the component.
2. Inspect the inside of the tube (2) and tube rod (3) for
scoring and other damage. If the tube or tube rod are
damaged, replace it with new parts.
3. Remove small scratches on the rod or inside of the
tube or tube rod with very fine grit emery cloth. Use
the emery cloth in a rotary motion to polish out small
imperfections in the metal and blend scratch(es) into
the surrounding surface.
4. Clean the parts with trichlorethylene after repair.
5. Check that the rod assembly (5) is straight. If the rod
assembly is bent, install a new rod assembly.
6. Check that the tube rod (3) is straight. If the tube rod
is bent, install an new tube rod.
e. Fork Side Shift Cylinder Assembly
Note: Follow Section 9.14.3, General Cylinder Assem-
bly Instructions.
1. Install a new oiled back-up ring (17) and o-ring (16)
into the groove on the outside of the guide (11).
2. Install a new oiled poly seal (19) into the inside of the
guide (11). Use tools that will not damage the seals.
3. Install a new oiled AN series wiper ring (18) into the
guide (11). The angled edge of the wiper must point
toward the outside edge of the guide.
4. Lubricate the seals on the inside of the guide (11)
and carefully slide the guide onto the tube rod (3).
5. Apply a drop of Loctite 242 (blue) removable
threadlocker to the first two threads of the tube rod
(3) 180° apart. Install the piston (12) onto the tube
rod (3) and tighten securely.
Model MMV Rev. 12/04
6. Apply Loctite 242 (blue) removable threadlocker to
the threads of the setscrew (15) and thread into the
piston (12). Tighten the setscrew securely.
7. Install a new oiled o-ring (14) and piston seal (13)
onto the piston (12).
IMPORTANT: Avoid using excess force when clamping
the cylinder tube in a vise. Apply only enough force to
hold the cylinder securely. Excessive force can damage
the cylinder tube (2).
8. Fasten the tube (2) in a soft-jawed vise or other
suitable holding device.
9. Lubricate the o-ring and seal on the piston and the
inside of the tube (2) with clean, filtered hydraulic oil.
This will aid in installation.
IMPORTANT: Use a suitable installation tool or com-
pression sleeve to help prevent twisting or damaging the
seals and o-rings when installing the piston (12) into the
cylinder tube (2). When sliding the tube rod and piston
assembly in the tube, DO NOT damage the piston by
scraping it against the threads in the tube. Keep the tube
rod in line with the tube to prevent binding.
10. Keep the tube rod (3) straight and carefully insert the
rod into the tube (2). Avoid scratching, nicking or
damaging the tube while installing the rod.
11. Apply a drop of Loctite 242 (blue) removable
threadlocker to the first two threads of the guide (11)
180° apart. Slide the guide down the tube rod and
thread into the cylinder tube (2) and tighten securely.
12. Install the three new oiled cast iron piston rings (6)
onto the piston end of the rod assembly (5).
Carefully slide the rod assembly into the tube rod (3).
13. Install a new oiled back-up ring (8) and o-ring (7)
onto the guide (4).
14. Install a new oiled poly seal (10) into the inside of the
guide (4).
15. Install a new oiled AN series wiper ring (9) into the
guide (4). The angled edge of the wiper must point
toward the outside edge of the guide.
16. Lubricate the seal and wiper inside the guide with
clean filtered hydraulic oil. This will aid in assembly
of the guide onto the rod assembly.
17. Apply a drop of Loctite 242 (blue) removable
threadlocker to the first two threads of the guide (4)
180° apart. Slide the guide onto the rod assembly (5)
and thread into the tube rod (3) and tighten securely.
Hydraulic System
9.179