Medium Duty Operator's Manual - Peterbilt Motors Company

Front Axle and Suspension
Torque
CAUTION: Do not spray the suspension with
chemical products or mineral oil; it can cause
damage to the bushings.
U–Bolts, Spring and Shackle Pinch Bolts
It is important that U–bolts remain tight. Severe use of your
vehicle will cause them to loosen faster. But all vehicles need
to have their U–bolts checked and tightened regularly. See
“Maintenance Schedule” on page 153. Be sure someone
with the proper training and the right tools checks and tightens
the U–bolts on your Medium Duty.
New springs can “settle in” after service, relieving the tension
on the U–bolts. Loose U–bolts can cause leaf spring breakage,
axle misalignment, hard steering and abnormal tire
wear.
• All vehicles should have suspension U–bolts tightened
after the first 500 miles (800 km) of operation. Torque the
front suspension U-bolts to 245-300 lb. ft. (333-408
N.m.)
Preventive Maintenance
WARNING! Do not operate the vehicle if the U–
bolts are not properly tightened. Loose U–bolts
do not properly secure the axle to the suspension.
This could cause loss of vehicle control
and an injury accident. Loose U–bolts can also
cause uneven tire wear and poor alignment.
U–bolts are difficult to tighten unless you have the right
equipment. If you cannot tighten them correctly yourself, be
sure to have them checked and tightened regularly by an
authorized mechanic.
WARNING! Do not replace U–bolts and nuts with
common U–bolts or standard nuts. Use only U–
bolts and nuts of SAE Grade 8 specification or
better.These parts are critical to vehicle safety. If
the wrong U–bolts or nuts are used, the axle
could loosen or separate from the vehicle and
cause a serious injury accident.
• At the same time U-bolts are tightened, re-torque the
spring and shackle pinch bolts to 105 lb. ft. (142 N. m.)
– 242 – Y53-6008A Medium Duty (R05/09)