Operating Instructions Driving Tips And Techniques
Medium Duty
(R10/06) Y53-6008 – 101 –
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 load-
ing. 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 deflat-
ing the suspension.
WARNING! Do not operate the Air Suspension
Deflate Switch (Dump Valve) while driving. Sud-
den deflation while your vehicle is moving can
affect handling and control and could lead to an
accident. Use this switch only when your vehicle
is not moving.
CAUTION: Operating a vehicle with air suspen-
sion bags either overinflated or underinflated
may cause damage to driveline components. If a
vehicle must be operated under such condi-
tions, do not exceed 5 mph (8 km/h).
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 pre-mature 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 val-
ues are shown in the illustration and table below.
Air Suspension Deflate Switch
AIR
SPSN
DEFLATE
NORMAL
