JLG 740A, Service And Maintenance Manual

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SECTION 5 - HYDRAULICS
3121160 – JLG Lift – 5-13
12. Using all applicable safety precautions, operate the
boom functions. Check for correct operation and
hydraulic leaks. Secure as necessary.
13. Check fluid level of hydraulic tank and adjust as nec-
essary.
Tower Boom Lift Cylinder Removal
1. Place machine on a flat and level surface. Place the
main boom in a horizontal position with the tele-
scope cylinder fully retracted. Place the tower boom
in a fully elevated and fully retracted position.
2. Support the main boom, upright, and tower boom
with adequate overhead crane.
3. Adequately support the tower lift cylinder.
4. Remove mounting hardware securing the lift cylin-
der rod pin to the tower boom. Using a suitable
brass drift, drive out the tower lift cylinder rod attach
pin.
5. Using all applicable safety precautions, operate aux-
iliary power, activate tower lift down and fully retract
lift cylinder.
6. Tag, disconnect and cap the tower lift cylinder
hydraulic lines and ports.
7. Remove mounting hardware securing the tower lift
cylinder barrel pin to the turntable. Using a suitable
brass drift, drive out the tower lift cylinder barrel pin.
8. Carefully remove the tower lift cylinder from turnta-
ble. Place in a suitable work area.
Tower Lift Cylinder Installation
1. With the main boom and tower boom supported.
Place the tower lift cylinder in position on the turnta-
ble and secure in place.
2. Align holes in turntable and lift cylinder. Using a suit-
able rubber mallet, install the cylinder barrel pin and
secure with mounting hardware.
3. Remove caps from temporary hydraulic lines and
attach to lift cylinder ports. Using auxiliary power,
activate tower lift function and extend cylinder rod
until the cylinder rod bushing aligns with bushings
on boom.
4. Using an appropriate brass drift, drive the tower lift
cylinder rod end attach pin through the aligned
bushings. Secure pin with attaching hardware.
5. Remove temporary hydraulic lines from cylinder
ports and cap lines.
6. Remove caps from cylinder hydraulic lines and cor-
rectly install lines to cylinder as previously tagged.
7. Remove main boom support and overhead crane
supporting the upright. Activate hydraulic system.
8. Using all applicable safety precautions, operate the
boom functions. Check for correct operation and
hydraulic leaks. Secure as necessary.
9. Check fluid level of hydraulic tank and adjust as nec-
essary.
Slave Cylinder Removal
1. Place the machine on a flat surface and lower the
main boom and tower boom to the lowest position.
2. Using auxiliary power, retract the slave cylinder rod
completely.
3. Using a suitable lifting device, properly secure the
platform to prevent the platform from tilting back-
ward or forward during removal of the slave cylinder.
4. Mark and disconnect the slave cylinder hydraulic
hoses. Cap hoses to prevent the hydraulic system
from being contaminated.
5. Properly secure the slave cylinder by using a suit-
able sling or support.
6. Remove the slave cylinder pin retaining hardware.
Using a suitable brass drift, remove the slave cylin-
der pins from the rod and barrel ends.
7. Carefully remove the slave cylinder.
8. Clean and inspect the cylinder pins and retaining
hardware for reuse. replace if necessary.
Slave Cylinder Installation
1. Remove fittings from old cylinder and install in new
slave cylinder. Plug the port block holes in the old
cylinder with the plugs removed from the new cylin-
der.
2. Position the new cylinder in place using suitable
slings or support. Align barrel end mounting holes
with main fly holes.
3. Using a suitable plastic or rubber hammer, drive the
barrel end attach pin into place and install retaining
hardware.
4. Remove caps from hydraulic hoses and attach
hoses to proper cylinder port.
5. Using auxiliary power, extend the slave cylinder rod
until the rod attach pin hole aligns with those in the
platform pivot. Using a suitable plastic or rubber
hammer, drive the pin in place and install the retain-
ing hardware.
6. Remove sling from the slave cylinder and support
from platform.