Peterbilt Medium Duty Trucks Operator's Manual after 1-07

Operating Instructions
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.
DEFLATE
AIR
NORMAL
SPSN
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. 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 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 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 values
are shown in the illustration and table below.
Medium Duty (R10/06) Y53-6008 – 101 –