OPERATING CONTROLS AND PROCEDURES RT770E OPERATOR MANUAL
3-34 Published 04-04-2017, Control # 446-09
1. Lock the differentials by pressing and holding the Axle
Differential Control Switch in the lock position;
disengage the function by releasing the switch.
2. Lock/unlock the differentials only when the vehicle is
standing still or moving at a constant low speed with the
wheels not slipping.
3. Locked differentials cause the crane’s turning radius to
increase, creating an understeer condition; use caution,
good judgement and drive at low speeds when operating
the vehicle with locked differentials.
4. Lock the differentials only when maximum traction is
needed on poor road or highway surfaces.
5. Always unlock the differentials when the need for
maximum traction has passed or when traveling on good
road or highway surfaces.
Operation
The differential lock function should preferably be engaged
when the crane is stationary but may be engaged when
moving, if the following conditions are met:
1. The crane is moving very slowly (creep speed).
2. The wheels are not spinning at the time of engagement.
When traveling with the differentials locked, do not deviate
from a straight path more than is absolutely necessary.
Engage the differential locks by doing the following:
1. Position the Axle Differential lock Control Switch to the
locked position with the crane stationary or moving at a
slow speed.
If moving at a slow speed, let up momentarily on the
Foot Throttle Pedal to relieve torque on the differential
gearing. This will fully engage the differential locks.
NOTE: When the differentials are locked, the Axle
Differential Locked Indicator illuminates.
2. Proceed over the poor road condition cautiously.
When the adverse condition has passed, disengage the
differential locks by doing the following:
1. Release the Axle Differential Lock control Switch,
allowing it to return to the unlocked position while
maintaining a slow speed.
2. Let up momentarily on the Foot Throttle Pedal to relieve
torque on the differential gearing, allowing the
differential to fully unlock.
NOTE: When the differentials are unlocked, the Axle
Differential Locked Indicator will not be illuminated.
3. Resume driving at a normal speed using good driving
judgement.
Axle Oscillation Lockouts Operation
The following procedure should be used to periodically
check the axle oscillation system and ensure that it is in
proper working condition.
1. Ensure the tires are inflated to the recommended
pressure. Refer to the Load Chart Book in the crane cab
for proper inflation pressures.
2. With the hook unloaded, the boom fully retracted and
centered over the front at no more than a 10° to 15°
boom angle, position the crane on a block or curb so that
one rear tire is approximately 15 to 30 cm (6 to 12 in)
above the level of the opposite tire.
3. Slowly swing the superstructure to the left or right until
the axle oscillation lockout valve is activated. This will
lock the rear axle out of level. Do not swing beyond the
tire track.
4. After engaging the swing brake, slowly drive off of the
block or curb and stop. The rear tires should both be
touching the road surface and the opposite front tire
should be light or slightly off the road surface.
5. Release the swing brake and swing the superstructure
until it is centered over the front.
If the axle oscillation lockout valve is functioning
properly, the crane will re-level itself; if the valve is not
working properly, the crane will not re-level itself. If the
CAUTION
Possible Machine Damage!
When driving on hard, dry surfaces with the differentials
locked, do not turn the wheels. Damage to the drive line
components can result.
Do not lock the differentials when the wheels are slipping.
Damage to the differentials can result.
CAUTION
Possible Loss of Vehicle Stability!
Do not lock the differentials when the vehicle is traveling
down steep grades and traction is minimal.
DANGER
Tipping Hazard!
Do not operate the crane if the axle oscillation lockout
system is not functioning properly.
Failure to comply with this warning may result in death or
serious injury.
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