JLG 740AJ, Service And Maintenance Manual

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SECTION 3 - CHASSIS & TURNTABLE
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Troubleshooting
Table 3-3. Excessive Noise and/or Vibration
Item Description Action
Check oil level in reservoir and oil
supply to the motor. Insufficient hydraulic fluid could lead to cavitation that would cause
system noise. Fill the reservoir to the proper level and ensure that oil supply to the motor
is adequate and the lines are unobstructed.
Check for air in the system. Air trapped within the system lines, or the motor itself, could result in
cavitation that would cause system noise. Ensure that all of the system lines and components are purged of air.
Inspect the output shaft cou-
plings. A loose or incorrect shaft coupling will produce vibrations that could
result in system noise. Ensure that the correct coupling is used and that it fits properly onto the
shaft.
Inspect the output shaft align-
ment. Misaligned shafts create excessive frictional vibration that could result
in system noise. Ensure that the shafts are properly aligned.
Hydraulic oil viscosity above limits. Viscosity above acceptable limits will result in cavitation that would
lead to system noise.
Replace hydraulic oil with appropriate fluid for operating conditions.
Table 3-4. System Operating Hot
Item Description Action
Check oil level in reservoir and oil
supply to the pump. Insufficient amount of hydraulic fluid will not meet the cooling
demands of the system. Fill the reservoir to the proper level.
Inspect the heat exchanger, (if so
equipped). If the heat exchanger fails, or becomes obstructed, it may not meet the
cooling demands of the system. Ensure that heat exchanger is receiving adequate air flow and that the
heat exchanger is in good operating condition. Repair or replace as neces-
sary.
Check the system relief valves. If a system relief valve becomes unseated for an extended period of time
or fails for any other reason, the system could become overheated. Repair or replace any malfunctioning relief valves as applicable and verify
that the loads on the machine are not excessive.
Table 3-5. Won’t Shift or Slow to Start
Item Description Action
Check the signal line to the servo
control port. Obstructed or restricted flow through the servo control signal lines could
result in slow shift or no shift conditions within the motor. Ensure that the signal lines are not obstructed or restricted and that signal
pressure is adequate to shift the motor.
Check that the correct supply and
drain orifices are properly
installed, and are not obstructed. Supply and drain orifices determine the shift rate of the motor. The
smaller the orifice, the longer the time it takes to shift the motor.
Obstruction will also increase shift times. Ensure that the proper control orifices are installed in the motor and verify
that they are not obstructed. Clean or replace as necessary.