JLG 120HX Service Manual - Manual (Page 33)

SECTION 2 - PROCEDURES
3120819 – JLG Lift – 2-11
2.10 CYLINDER REMOVAL AND
INSTALLATION
Telescope Cylinder Removal
1. Place machine on a flat and level surface, with axles
extended and the boom fully retracted and in the
horizontal position.
2. Shut down engine. Support boom platform end with
a prop or suitable overhead lifting device.
3. Remove boom end cover.
4. Remove boom length/angle indicator from boom
assembly.
HYDRAULIC LINES AND PORTS SHOULD BE CAPPED IMMEDI-
ATELY AFTER DISCONNECTING LINES TO AVOID THE ENTRY OF
CONTAMINANTS INTO THE SYSTEM.
5. Tag and disconnect hydraulic lines to telescope cyl-
inder. Use suitable containers to retain any residual
hydraulic fluid. Cap hydraulic lines and ports.
HYDRAULIC LINES AND PORTS SHOULD BE CAPPED IMMEDI-
ATELY AFTER DISCONNECTING LINES TO AVOID THE ENTRY OF
CONTAMINANTS INTO THE SYSTEM.
6. Tag and disconnect hydraulic lines to telescope cyl-
inder. Use suitable containers to retain any residual
hydraulic fluid. Cap hydraulic lines and ports.
7. Remove the two (2) cotter pins that retain the tele-
scope rod attach pin to the base boom.
8. Using a suitable brass drift, carefully drive the tele-
scope cylinder rod attach pin from the base boom.
9. Remove the telescope cylinder trunnion attach pin
cover from each side of the base boom.
10. Remove the setscrews securing the telescope cylin-
der attach pin from each side of the telescope cylin-
der trunnion.
11. Using a suitable slide hammer, remove the half pins
attaching the telescope cylinder to the inner mid
boom section.
12. Attach a suitable sling to the telescope cylinder rod.
Support with an overhead crane or other suitable lift-
ing device.
13. Remove the rod support bracket at the aft end of the
base boom.
14. Remove the two (2) extension chain adjusting nuts
at the aft end of the base boom.
15. Remove the three (3) bolts, washers and lockwash-
ers attaching the chain adjust bracket to the aft end
of the base boom and remove bracket.
16. Pull boom sections apart several feet.
17. Using the lifting equipment, raise the cylinder to
obtain sufficient clearance for removal of the cylin-
der.
18. Connect a suitable lifting device to the extension
chain adjust rod on top of the telescope cylinder.
19. Using both lifting devices, carefully pull the cylinder
from the boom assembly.
NOTE: The extension rod will come out of the boom twice as
far as the telescope cylinder proportionally.
20. Continue sliding the cylinder and extension rod out
of the boom until the rod can be separated from the
extension chain by removing the chain clevis attach
pin.
21. Using the lifting equipment, remove the extension
chain bar.
22. Continue sliding the cylinder from the boom, laying
the extension chain on top of the base boom as the
cylinder is coming out.
23. Using another lifting device, support the sheave
wheel end of the cylinder and remove the cylinder
from the boom assembly.
24. Carefully lift the cylinder clear of the boom assembly
and lower to the ground or suitably supported work
area.
Telescope Cylinder Installation
1. Using suitable lifting equipment, carefully lower the
cylinder to the boom assembly.
2. Using another lifting device, support the sheave
wheel end of the cylinder and install the cylinder into
the boom assembly.
3. Slide the extension cylinder into the boom, sliding
the extension chain in place as the cylinder is mov-
ing in.
4. Using the lifting equipment, install the extension
chain bar.
5. Continue sliding the cylinder and extension rod into
the boom until the rod can be attached to the exten-
sion chain by installing the chain clevis attach pin.
6. Install the chain adjust bracket and install the three
(3) bolts, washers and lockwashers which attach the
bracket to the aft end of the base boom.