JLG T350 Service Manual - Manual (Page 89)

SECTION 3 - CHASSIS & TURNTABLE
3121198 – JLG Lift – 3-53
Wear Tolerance
1. From the underside of the machine, at rear center,
with the main boom fully elevated and fully retracted,
using a magnetic base dial indicator, measure and
record the distance between the swing bearing and
turntable. See Figure 3-17., Swing Bearing Toler-
ance Measuring Point
2. At the same point, with the main boom at horizontal
and fully extended, using a magnetic base dial indi-
cator, measure and record the distance between the
swing bearing and turntable. See Figure 3-17.,
Swing Bearing Tolerance Measuring Point.
3. If a difference greater than 0.057 in. (1.40 mm) is
determined, the swing bearing should be replaced.
4. If a difference less than 0.057 in. (1.40 mm) is deter-
mined, 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.
THE SWING BEARING IS ONE OF THE MOST CRITICAL POINTS ON
AN AERIAL LIFT. IT IS HERE THAT THE STRESSES OF LIFTING
ARE CONCENTRATED, AT THE CENTER OF ROTATION. BECAUSE
OF THIS, PROPER MAINTENANCE OF THE SWING BEARING
BOLTS IS A MUST FOR SAFE OPERATION.
Swing Bearing Removal
1. From Ground Control station, operate the boom until
it is horizontal.
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.
HYDRAULIC LINES AND PORTS SHOULD BE CAPPED IMMEDI-
ATELY AFTER DISCONNECTING LINES TO AVOID THE ENTRY OF
CONTAMINANTS INTO THE SYSTEM.
3. Tag and disconnect the hydraulic lines from the fit-
tings on the turntable. Use a suitable container to
retain any residual hydraulic fluid. Immediately cap
lines and ports.
4. Attach suitable overhead lifting equipment to the
base of the turntable weldment.
5. 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.
6. Use the lifting equipment to carefully lift the com-
plete turntable assembly from the bearing. Ensure
that no damage occurs to the turntable, bearing or
frame-mounted components.
7. Carefully place the turntable on a suitably supported
trestle.
8. Use a suitable tool to scribe a line on the outer race
of the swing bearing and the frame. This line will aid
in aligning the bearing upon installation. Remove the
bolts and washers which attach the outer race of the
bearing to the frame. Discard the bolts. Use suitable
lifting equipment to remove the bearing from the
frame, then move the bearing to a clean, suitably
supported work area.
Figure 3-17. Swing Bearing Tolerance Measuring Point