operators_manual

and the axle is in its up position. Axle creep
ratings are assigned by the axle
manufacturer and are based on axle model
and intended service of the vehicle.
Contact an authorized dealership if you are
unable to identify the axle creep rating of
this vehicle.
• Liftable/steerable (axle lift
calibration required)
• Liftable/non-steerable (axle lift
calibration required)
• Non-liftable (some suspensions
require dump valve calibration)
WARNING
Do not operate or park the vehicle with
auxiliary axles in the down/ loaded po-
sition when vehicle is unladen, or is
being unloaded. Raise or dump air into
driver controlled auxiliary axle(s) prior
to unloading vehicle. Failure to do so
can result in loss of vehicle control or
rollaway that may result in death, per-
sonal injury, equipment or property
damage.
Related concepts
Auxiliary Axle Pressure Regulator
Information on using the auxiliary axle
pressure regulator.
Vehicles with liftable auxiliary axles will
have knobs available to adjust the
pressure in the auxiliary axle suspension.
These knobs are in addition to the tag and
pusher axle switches that control the axle
position.
Adding more pressure to the auxiliary axle
will increase the pressure the auxiliary axle
pushes down. Increasing pressure will
decrease load on the drive axles and will
descrease traction. Decreasing pressure
will transfer more weight to the drive axles
and will result in more traction from the
drive axles.
Deflate the auxiliary axle suspension
before coupling or uncoupling a trailer.
After the trailer is coupled or de-coupled,
then increase pressure to balance traction
and axle load requirements. Inflate air
springs of the auxiliary axles to the desired
pressure after coupling to a loaded trailer
while still maintaining proper traction of the
drive axles.
Adjust the pressure regulator control knob
to a lower pressure until desired traction is
obtained. By reducing air pressure at
pusher or tag axle, load will be transferred
to drive axles. Do not overload drive axles.
Always deflate air springs of the auxiliary
axles before attempting to unload vehicle.
This allows maximum traction of the drive
axles to control the vehicle.
Depending on the suspension, various
calibrations may be required. Contact your
authorized dealer or axle/suspension
manufacturer for specific calibration
procedures.
Some suspensions require dump valve
calibration. For example, some dead axles
do not lift, but the air can be dumped out of
them to unload them when empty. Air
pressure is controlled via an adjustable
regulator. These axles need to be
calibrated for load.
Contact your authorized dealer or axle/
suspension manufacturer for dump valve
calibration procedures.
What is Axle Creep Rating
Vehicles outfitted with auxiliary axles, and
full truck configuration, will have an axle
creep rating which defines how much load
is allowed when the vehicle has a full load
and manuevering the vehicle, at very slow
speeds, with auxiliary axles in the up
position. In these situations, the load
DRIVING - Axle and Suspension
Y53-6047-2HEN (03/18) 159
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