Peterbilt Medium Duty Truck Owner's Manual - Peterbilt Motors

STARTING AND OPERATING THE VEHICLE
DRIVING TIPS AND TECHNIQUES
Air Suspension Height/Air Pressure
Your vehicle may have an air suspension. A deflation
switch on the dash allows you to exhaust the air in the
suspension, which allows you to lower the height of your
vehicle for loading. On tractors, the deflate switch allows
you to lower the fifth wheel to slide under a trailer.
A guard on the switch prevents you from accidentally
deflating the suspension.
WARNING! Do not operate the Air Suspension
Deflate Switch (Dump Valve) while driving.
Sudden deflation while your vehicle is moving
can affect handling and control and could
lead to an accident possibly resulting in death
or personal injury. Use this switch only when
your vehicle is not moving.
CAUTION: Operating a vehicle with air suspension
bags either overinflated or underinflated
may cause damage to driveline
components. If a vehicle must be operated
under such conditions, do not exceed 5 mph
(8 km/h).
AIR SUSPENSION
Air Suspension Deflate Switch
Setting Ride Height
Vehicles equipped with rear air suspensions have their
ride height and axle (pinion) angle(s) preset at the factory.
These are precision settings and should not be altered.
Incorrectly adjusted ride height may result in improper
interaxle U-joint working angles. This can result in premature
driveline wear and driveline vibration. If your vehicle
is equipped with a Peterbilt rear air suspension, and if
it becomes necessary to reset the ride height, you may
temporarily set it by following the next procedure. Proper
ride height measurement and values are shown in the
illustration and table below.
Medium Duty (R05/09) Y53-6027 – 133 –