JLG 740AJ Service Manual - Manual (Page 297)

SECTION 5 - HYDRAULICS
3121160 – JLG Lift – 5-11
6. Remove mounting hardware securing the Main Lift
Cylinder rod end to the base boom.
7. Using a suitable brass drift, carefully drive main lift
cylinder rod end pin from the base boom.
8. Use the auxiliary control to retract the main lift cylin-
der.
9. Remove mounting hardware securing the main
boom telescope cylinder, barrel end to the main
base boom.
10. Attach a suitable sling to the telescope cylinder.
Using a suitable lifting device attached to the sling,
carefully pull the cylinder partially from the front end
of boom assembly (thru tower upright upper access
hole).
11. Secure the cylinder with a suitable sling and lifting
device at the approximate center of gravity.
12. Carefully lift the cylinder clear of the boom assembly
and lower to the ground or suitably supported work
area.
Main Boom Telescope Cylinder Installation
1. Attach a hydraulic power supply to the telescope
cylinder ports. Using suitable supports or lifting
devices at each end of the cylinder, extend the rod
so that the cylinder pin attach holes are the same
distance apart as the boom pin attach holes.
2. Using suitable lifting equipment, carefully insert the
cylinder into the boom assembly.
3. Install the cylinder into the boom assembly.
4. Remove the lifting devices from the telescope cylin-
der.
5. Carefully install telescope cylinder rod pin #1
through the fly boom and secure it with the retaining
rings.
6. Carefully install the telescope cylinder barrel end
support into mounting block in base boom and
secure with blocks and bolts. Use Loctite #242 on
bolts. Shim as necessary.
7. Remove applicable hydraulic line and port caps and
correctly connect the hydraulic lines to the tele-
scope cylinder. Ensure all hoses are correctly
routed.
8. Extend the main lift cylinder using the auxiliary con-
trol to align with rod end hole in main base boom
9. Carefully insert the main lift cylinder rod end pin
through the base boom and install the mounting
hardware.
10. Remove boom prop and overhead crane. Activate
hydraulic system.
11. Using all applicable safety precautions, operate the
boom functions. Check for correct operation and
hydraulic leaks. Secure as necessary.
12. Check fluid level of hydraulic tank and adjust as nec-
essary.
Main Lift Cylinder Removal
1. Place the machine on a flat and level surface. Attach
a suitable lifting device and sling, sufficient to lift the
main boom assembly, to the approximate center of
the main boom assembly.
2. Remove the hardware retaining the main lift cylinder
rod attach pin to the boom. Using a suitable brass
drift, drive out the cylinder rod attach pin.
3. Using auxiliary power, retract the lift cylinder rod
completely.
4. Disconnect, cap and tag the main boom lift cylinder
hydraulic lines and ports.
5. Attach a suitable lifting device and sling to the main
lift cylinder
6. Remove barrel end attach pin retaining hardware.
7. Using a suitable brass drift drive out the barrel end
attach pin from the tower upright.
8. Raise the main boom assembly with the lifting
device and sling to allow enough space to remove
the main lift cylinder from the upright top.
9. Carefully lift the cylinder clear of the boom assembly
and lower to the ground or suitably supported work
area.
10. Lower the boom assembly to the rest position.
Main Boom Lift Cylinder Installation
1. Using suitable lifting device and sling, lift the main
boom to allow enough space to lower the main lift
cylinder to align with pin mounting holes of the
tower fly boom and barrel end of main lift cylinder.
2. Using a suitable drift, drive barrel end attach pin
through the mounting holes in the lift cylinder and
the tower fly boom. Secure in place with the pin and
retaining hardware.
3. Remove cylinder port plugs and hydraulic line caps
and correctly attach lines to cylinder ports.
4. Using auxiliary power extend the cylinder rod until
the attach pin hole aligns with those in the main
boom. Using a suitable drift drive cylinder rod attach
pin through the aligned holes, taking care to align
the grooved pin holes. Secure the pin in place with
attaching hardware.