JLG 1250AJP Service Manual - Manual (Page 149)

SECTION 3 - 1CHASSIS & TURNTABLE
3121171 – JLG Lift – 3-101
Wear Tolerance
NOTE: In order to ensure the most accurate measurement,
place the indictor as close to the swing bearing as
possible.
NOTE: As distances increase from the bearing the potential
for inaccuracies and unwarranted bearing replace-
ment increases. If access to an area close to the
bearing is not possible the indicator may be installed
on the same plane as the bearing.
1. From the underside of the machine, at rear center,
with the main boom fully elevated and fully retracted,
as shown in Figure 3-52., Swing Bearing Tolerance
Boom Placement - Sheet 1 of 2, set up a magnetic
base dial indicator as shown below and set the indi-
cator to 0 (zero).
2. Next, position the main boom at horizontal and fully
extended, and the tower boom fully elevated and
fully extended as shown in Figure 3-53., Swing Bear-
ing Tolerance Boom Placement - Sheet 2 of 2. Read
the measurement recorded on the dial indicator
gauge.
3. If the measurement is greater than 0.094 in. (2.387
mm), the swing bearing should be replaced.
4. If the measurement is less than 0.094 in. (2.387
mm), and any of the following conditions exist, the
bearing should be removed, disassembled, and
inspected for the following:
a. Metal particles in the grease.
b. Increased drive power required.
c. Noise.
d. Rough rotation.
5. If bearing inspection shows no defects, reassemble
and return to service.
Swing Bearing Removal
1. From Ground Control station, operate the boom
adequately to provide access to frame opening to
rotary coupling.
NEVER WORK BENEATH THE BOOM WITHOUT FIRST ENGAGING
BOOM SAFETY PROP OR PROVIDING ADEQUATE OVERHEAD
SLING SUPPORT AND/OR BLOCKING.
2. Attach an adequate support sling to the boom and
draw all slack from sling. Prop or block the boom if
feasible.
3. From inside turntable, remove mounting hardware
which attach rotary coupling retaining yoke brackets
to turntable.
HYDRAULIC LINES AND PORTS SHOULD BE CAPPED IMMEDI-
ATELY AFTER DISCONNECTING LINES TO AVOID THE ENTRY OF
CONTAMINANTS INTO THE SYSTEM.
4. Tag and disconnect the hydraulic lines from the fit-
tings on the top of the rotary coupling. Use a suit-
able container to retain any residual hydraulic fluid.
Immediately cap lines and ports.
5. Attach suitable overhead lifting equipment to the
base of the turntable weldment.
6. Use a suitable tool to scribe a line on the inner race
of the swing bearing and on the underside of the
turntable. This will aid in aligning the bearing upon
installation. Remove the bolts and washers which
attach the turntable to the bearing inner race. Dis-
card the bolts.
Figure 3-54. Swing Bolt Feeler Gauge Check