Medium Duty Operator's Manual - Peterbilt Motors Company

Preventive Maintenance
WARNING! Do not replace U–bolts and nuts with
common U–bolts or standard nuts. 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. Use only U–bolts and nuts of SAE
Grade 8 specification or better.
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.
Suspension alignment should be checked when any one of
the following conditions exist:
• Discovery of loose suspension fasteners (Any
torque below the recommended torque value.).
• Discovery of elongated holes in a suspension component.
• Bushing replacement.
• Excessive or abnormal tire wear.
NOTE: To ensure an accurate torque reading, use
properly maintained and calibrated torque
wrenches.
Rear Axle and Suspension
Grade 5 Capscrew Torque Specifications
Capscrew Body
Torque
Size
(inches-thread)
Lb. ft. N.m.
1/4-20 6—9 8—12
-28 7—10 9.5—14
5/16-18 13—18 18—24
-24 14—20 19—27
3/8-16 22—32 30—43
-24 25—40 34—54
7/16-14 35—50 47—68
-20 39—56 53—76
1/2-13 54—77 73—104
-20 58—87 79—118
9/16-12 78—111 105—151
-18 87—124 118—168
5/8-11 108—154 147—209
-18 122—174 166—236
3/4-10 192—273 260—370
-16 214—305 290—414
7/8-9 309—441 419—598
-14 341—486 462—659
1 -8 464—662 629—898
1-12 508—724 689—982
Medium Duty (R05/09) Y53-6008A – 247 –