JLG G12-55A Service Manual - Manual (Page 40)

Boom
3-6 G10-55A, G12-55A
3.5 BOOM SECTION REMOVAL/
INSTALLATION
3.5.1 Second, Third & Fourth Boom Section
Removal
1. Remove any attachment from the quick switch
assembly. Refer to the appropriate operation and
safety manual.
2. Remove the quick switch assembly. Refer to Section
3.9.1, “Quick Switch Removal.”
3. If equipped, remove the Boom Head Mounted
Winch. Refer to Section 3.10.1, “Boom Head-
Mounted Winch Removal.”
4. Park the machine on a hard, level surface, level the
machine, fully retract the boom, level the boom,
place the transmission control lever in
(N) NEUTRAL, engage the park brake and shut the
engine OFF.
5. Place a Do Not Operate Tag on both the ignition key
switch and the steering wheel, stating that the
machine should not be operated.
6. Open the engine cover. Allow the system fluids to
cool.
7. Label and remove both tilt cylinder hoses (1)
between the tilt cylinder (2) and the hose carrier (3).
Label, cap and plug the hose carrier tube ends and
cylinder ports to prevent dirt and debris from
entering the hydraulic system.
8. Using a suitable lifting device, secure the tilt cylinder
barrel with a nylon strap.
9. Remove both retaining clips (4) from each side of
the tilt cylinder mounting pin (5).
10. Remove the tilt cylinder mounting pin (5).
11. Lower tilt cylinder from the boom head.
12. Support the front of the boom by placing a sling
behind the boom head.
13. Loosen the jam nut and lock nut (6) to release
tension from the hoses on the hose take-up
weldment (7).
14. Loosen the hydraulic hoses (8) and electrical cables
if equipped on the hose take-up weldment (7). Plug
the hose ends and tube ends to prevent dirt and
debris from entering the hydraulic system.
15. At the top front of the boom, measure and note the
distance from the end of the three extend chain
clevises (9) to the face of the lock nut (10).
16. Loosen and remove the lock nuts (10), adjusting
nuts (11), washers (12) and springs (13) from the
three extend chain clevises (9).
MY3770
1
2
3
4
5
MY4130
8 7 6
MY3580
11 10 13 12 9