JLG G12-55A Service Manual - Manual (Page 60)

Boom
3-24 G10-55A, G12-55A
To remove the retract chain from the fourth to second
boom sections:
1. Remove the jam nut (4) from the chain clevis
installed in the chain adjustment block.
2. Back off the adjusting nut fully on the chain clevis.
Do not remove the nut from the clevis.
3. Remove the chain from the clevis, install a nylon tie-
wrap through the holes in the chain, making a loop
with the tie-wrap and tie a rope to the loop.
4. Move to the back of the boom and pull the chain to
the rear to allow slack for removal.
5. Remove the chain from the clevis and drop it free
from the boom.
6. Holding the rope at the front, carefully pull the chain
out through the back of the boom until it’s free.
7. Untie the rope and leave it in place for reinstallation
of the chain.
3.10.2 Boom Retract Chain Installation
Inspect and lubricate chains thoroughly before
installation. Articulate the chains to make sure all working
surfaces are thoroughly lubricated.
Note: If the inner retract chain was removed, it must be
installed first.
1. Fasten a rope to the end of the 3/4 in. chain in order
to pull it back into the boom.
2. Attach chain to chain clevis at rear of boom.
3. Carefully pull the chain into the boom until it can be
fastened to the chain clevis.
4. Remove the rope.
5. Fasten the chain into the clevis by installing the pin
and retaining ring.
6. Torque the jam nuts to 100 lb-ft (135 Nm).
To install the outer retract chain:
1. Fasten a rope to the end of the chain in order to pull
it back into the boom.
2. Attach chain to chain clevis at rear of boom.
3. Carefully pull the chain into the boom until it can be
fastened to the chain clevis.
4. Remove the rope.
5. Fastened the chain into the clevis by installing the
pin and cotter pin.
6. Install the chain adjustment block and mounting
bolts. Torque the chain adjustment block mounting
bolts to 360-390 lb-ft (475-530 Nm).
7. Install extend/retract cylinder and cylinder support.
8. Adjust the retract chains as needed. Refer to Section
3.7, “Hose Carrier Assembly Removal/Installation.”
9. Properly connect the batteries.
10. Remove the Do Not Operate Tags from both the
ignition key switch and the steering wheel.
3.10.3 Boom Extend Chain Removal
The following section explains the removal of the extend
chains without removing the boom assemblies.
1. Park the machine on level ground. Place the
transmission control lever in (N) NEUTRAL, engage
the parking brake switch, level the boom, extend the
boom far enough to access the chain anchor and the
clevis through the top rear access hole, shut the
engine OFF.
2. Place a Do Not Operate Tag on both the ignition key
switch and the steering wheel.
3. Properly disconnect the batteries.
4. Secure the boom sections together to prevent
uncontrolled boom run out when the extend chains
are removed.
5. On the chain being removed, loosen and remove the
jam nut from the rear chain clevis and back off the
adjusting nut on the chain clevis to the end of the
threads. Do not completely remove the nut.
6. Remove the chain clevis pin and retaining ring to
free the chain.
7. Install the nylon tie wrap through the holes in the
chain, making a loop with the tie wrap and tie a rope
to the loop.
8. Pull slack to chain clevis at front of boom.
9. Remove the clevis pin and the retaining ring from the
chain and chain clevis.
10. Install a nylon tie wrap through the chain holes,
forming a loop and tie a rope to the loop.
11. Carefully pull the chain out of the boom.
12. Untie the rope and leave it in place for reinstallation
of the chain.