Vibration Types; Vibration Diagnosis - Jeep 1979 CJ-5 Technical & Service Manual

2H-10 WHEELS AND TIRES
eral or radial runout for reference.
On radial tires, radial runout should not exceed 0.080
inch (2.03 mm) and lateral runout should not exceed
0.100 inch (2.54 mm).
If the tire radial or lateral runout exceeds specified
limits, it will be necessary to check wheel runout to
determine whether the wheel or tire is at fault.
Wheel radial runout is measured at the wheel rim just
inside of the wheel cover retaining nibs (fig. 2H-14).
Wheel lateral runout is measured at the wheel rim bead
flange just inside the curved lip of the flange (fig. 2H-
14). Mark the high points of radial or lateral runout for
reference.
R A D I A L L Y L A T E R A L L Y
Fig. 2H-14 Measuring Wheel Runout
Wheel radial runout should not exceed 0.035 inch (0.88
mm). Wheel lateral runout should not exceed 0.045 inch
(1.14 mm).
If tire runout exceeds specified limits but wheel run-
out is within limits, runout may be reduced to an accept-
able level by changing tire position on the wheel so that
the previously marked high points are 180 degrees apart.
N O T E : On vehicles with disc brakes, excessive wheel
lateral runout may be caused by excessive rotor hub-to-
bore runout. Refer to the Rotor Inspection procedure in
Chapter 2G.
VIBRATION
Vibration may be caused by tire and wheel unbalance
or runout, incorrect wheel bearing adjustment, loose or
worn suspension or steering components, worn or defec-
tive tires, certain tire tread patterns, incorrect universal
joint angles, worn universal joints, excessive propeller
shaft runout or yoke runout, rotor or brakedrum runout,
loose engine or transmission supports, or by engine op-
erated accessories.
Vibration Types
There are two types of vibration which are referred to
as mechanical and audible.
Mechanical vibrations are felt through the seats,
floorpan, or steering wheel and usually produce some
visible motion in the rear view mirror, fenders, dash
panel, or steering wheel.
Audible vibrations are heard or sensed above normal
background noise and may or may not be accompanied
by a mechanical vibration. In some cases, they occur as a
droning or drumming noise while in other cases they
produce a buffeting sensation that is felt or sensed by
the driver rather than heard.
Vibration. Sonsitlwlty
Mechanical and audible vibrations are sensitive to
changes in engine torque, vehicle speed, or engine speed.
They usually occur within one, or sometimes two well-
defined ranges in terms of vehicle speed, engine rpm,
and torque application.
Torque Sensitive
This means the means the condition can be improved
or worsened by accelerating, decelerating, coasting, or
maintaining a steady vehicle speed and application of
engine torque.
Vehicle Speed Sensitive
This means that the vibration occurs at the same
speed and is not affected by engine torque, engine rpm,
or transmission gear selected.
Engine Speed Sensitive
This means that the vibration occurs at varying ve-
hicle speeds when a different transmission gear is se-
lected. It can sometimes be isolated by increasing or
decreasing engine speed with the transmission in
neutral.
Vibration Diagnosis
A proper vibration diagnosis should always begin
with a road test, corrective measures should not be
attempted until the vibration type, magnitude, and
speed range have been established by a road test.
Road Test
During the road test, drive the vehicle on a road that
is smooth and free of undulations. If vibration is appar-
ent, note and record the following:
• The speed range in which vibration occurs
• The type of vibration—mechanical or audible
• I f the vibration is affected by changes in Vehicle
speed, engine rpm, or engine torque
• Determine the vibration sensitivity—torque sensi-
tive, engine speed sensitive, or vehicle speed
sensitive