JLG G12-55A Service Manual - Manual (Page 51)

3-17 G10-55A, G12-55A
Boom
4. Attach a suitable sling to the extend/retract cylinder.
Remove the extend/retract cylinder support.
5. Remove the rod end pin and lower the cylinder onto
the frame rails. Lowering the extend/retract cylinder
will allow access to the chains.
6. Remove tension from the chain by backing off the
jam nut and adjusting nut (1).
7. Remove the four bolts (2) from the chain adjustment
block.
8. Remove the chain from the clevis (3) at the block.
9. Install a nylon tie wrap through the holes of the
removed chain, making a loop with a tie wrap and tie
a rope to the loop.
10. At the rear of the boom, pull the chain to the rear to
allow slack for removal.
11. Remove the chain from the clevis and drop it free
from the boom.
12. Holding a rope at the front adjustment block,
carefully pull the chain out through the back of the
boom.
13. Untie the rope and leave it in place for reinstallation
of the chain.
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.
3.6.2 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 the chain to the chain clevis at the rear of the
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 the chain to the chain clevis at the rear of the
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 the extend/retract cylinder and cylinder
support.
8. Adjust the retract chains as needed. Refer to Section
3.7, “Boom Section Separation Adjustment.”
9. Properly connect the battery.
10. Remove the Do Not Operate Tags from both the
ignition key switch and the steering wheel.
3.6.3 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.
MX0510
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