Dodge RAM TRUCK 1500 1995 Service Manual page 1623

BR
WHEELS AND TIRES 22-11
V E H I C L E V I B R A T I O N
Vehicle vibration can be caused by:
• Tire/wheel unbalance or excessive runout
• Defective tires with extreme tread wear
® Nylon overlay flat spots (performance tires only)
• Incorrect wheel bearing adjustment (if applicable)
• Loose or worn suspension/steering components
• Certain tire tread patterns
• Incorrect drive shaft angles or excessive drive
shaft/yoke runout
• Defective or worn U-joints
® Excessive brake rotor or dram runout
• Loose engine or transmission supports/mounts
• And by engine operated accessories
Refer to the appropriate groups in this man­
ual for additional information.
VIBRATION TYPES
There are two types of vehicle vibration:
• Mechanical
• Audible.
Mechanical vehicle vibration can be felt through
the seats, floor pan and/or steering wheel.
Audible vehicle vibration is heard above normal
background noise. The sound can be a droning or
drumming noise.
Vibrations are sensitive to change in engine torque,
vehicle speed or engine speed.
ENGINE TORQUE SENSITIVE VIBRATION
This vibration can be increased or decreased by:
• Accelerating
• Decelerating
• Coasting
• Maintaining a constant vehicle speed
VEHICLE SPEED SENSITIVE VIBRATION
This vibration condition always occurs at the same
vehicle speed regardless of the engine torque or en­
gine speed.
ENGINE SPEED (RPM) SENSITIVE VIBRATION
This vibration occurs at varying engine speeds. It
can be isolated by increasing or decreasing the en­
gine speed with the transmission in NEUTRAL posi­
tion.
VIBRATION OIAGNOSIS
A vibration diagnosis should always begin with a
10 mile (16 km) trip (to warm the vehicle and tires).
Then a road test to identify the vibration. Corrective
action should not be attempted until the vibration
type has been identified via a road test.
During the road test, drive the vehicle on a smooth
surface. If vibration exists, note and record the fol­
lowing information:
© Identify the vehicle speed range when the vibra­
tion occurs
• Identify the type of vibration
® Identify the vibration sensitivity
® Determine if the vibration is affected by changes
in vehicle speed, engine speed and engine torque.
When the vibration has been identified, refer to the
Vibration Diagnosis chart for causes. Consider cor­
recting only those causes coded in the chart that are
related to the vibration condition.
Refer to the following cause codes and descriptions
for explanations when referring to the chart.
TRR—Tire and Wheel Radial Runout: Vehicle
speed sensitive, mechanical vibration. The runout
will not cause vibration below 20 mph (32 km/h).
WH—Wheel Hop: Vehicle speed sensitive, me­
chanical vibration. Wheel hop generates rapid up-
down movement in the steering wheel. The vibration
is most noticeable in the 20 - 40 mph (32 - 64 km/h)
range. The wheel hop will not cause vibration below
20 mph (32 km/h). Wheel hop is caused by a tire/
wheel that has a radial runout of more than 0.045 of-
an-inch (1.14 mm). If wheel runout is acceptable and
combined runout cannot be reduced by repositioning
the tire on wheel, replace tire.
TB—Tire/Wheel Balance: Vehicle speed sensitive,
mechanical vibration. Static tire/wheel unbalance
will not cause vibration below 30 mph (46 km/h). Dy­
namic tire/wheel unbalance will not cause vibration
below 40 mph (64 km/h).
TLR—Tire/Wheel Lateral runout: Vehicle speed
sensitive, mechanical vibration. The runout will not
cause vibration below 50 - 55 mph (80 - 88 km/h). Ex­
cessive lateral runout will also cause front-end
shimmy.
TW—Tire Wear: Vehicle speed sensitive, audible
vibration. Abnormal tire wear causes small vibration
in the 30 - 55 mph (88 km/h) range. This will pro­
duce a whine noise at high speed. The whine will
change to a growl noise when the speed is reduced.
W—Tire Waddle: Vehicle speed sensitive, mechan­
ical vibration. Irregular tire uniformity can cause
side-to-side motion during speeds up to 15 mph (24
km/h). If the motion is excessive, identify the defec­
tive tire and replace it.
UAJ—Universal Joint (Drive Shaft) Angles:
Torque/vehicle speed sensitive, mechanical/audible vi­
bration. Incorrect drive shaft angles cause mechani­
cal vibration below 20 mph (32 km/h) and in the 70
mph (112 km/h) range. The incorrect angles can also
produce an audible vibration in the 20 - 50 mph (32 -
80 km/h) range. Caster adjustment could be required
to correct the angles.
UJ—Universal Joints: Engine torque/vehicle
speed sensitive, mechanical/audible vibration. If the