Diagnosing Second-Order Driveline Vibration - GMC chevrolet camaro 2000 Service Manual

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Diagnosing Second-Order Driveline
) Vibration
Second-Order Driveline Vibration. Theory
182178
A faulty universal joint (U-joint) may cause a vibration
that occurs twice for each rotation of the propeller
shaft. This type of vibration is called a second-order
vibration.
)
Second-order driveline vibrations are independent of
runout or balance of a driveline component
\
)
The following dei;,cription .of.basicU:-joint theory will
help you to understanc:l. where second-order driveline
~ibrations originate and why they 9ccur. ·
• As the propeller shaft rotates, the U-joint speeds
upand slows down twice for each rotation of
· the propeller shaft.
• . The aQc~lera.tion and c:lece.le.ration of the U-joint is
not visible. lfthere is vibration in the U-joint, the
acceleration an.d deceleration will be audible
and tactile.
• Compare the u:joibt in a vehicle to a .
universal-type soQket When a universaHype.
socket is used to tighten a bolt, the· socket will bind
and release as the socketturns .toward
90 degrees. The bind and release occurs twice for
each revolution of the socket. ·
• The U-joint in a vehicle works in the. same way as
the universal-type socket. .The bind and release
effect is directly proportional to the angle that
the U-joint operates: the greater the angle,
the greater the effect.
• Because the transmission output speed is
constant, the binding and releasing of the U-joint
is better described as an acceleration and
deceleration which occurs twice for each revolution
of the propeller shaft.
• If the propeller shaft is running slowly, the
accelerating and decelerating effect is visible. The
acceleration and deceleration may create a
vibration due to the fluctuations in force that are
generated at high speeds.
Vibration Diagnosis and Correction 0-61
Canceled Out Driveline Angles
Legend
(1) Front Working Angle
(2) Rear Working Angle
182180
Engineers design drivelines in order to compensate for
the accelerations and decelerations in order to ·
produce a smooth, constant flow of power, as
listed below: ·
• The transmissi.on drives .the front yoke of the
propeller shaft at a smooth and constant speed.
• The first U-joint causes the power to fluctuate
twice for each revolution of the propeller shaft.
• The second U-joint, oriented 90 degrees from the
first U-joint, causes the power to fluctuate
opposite that of the first U-joint.
• As the first U-joint slows down, the second U-joint
speeds up.
This design causes one U-joint to cancel· out the effect
of the othedJ-joint. The cancelled effects result in a
smooth, constant power flow from the output yoke
of the propeller shaft.
Second-order .driveline vibrations occur when the
cancellation becomes unequal between the front
U-joint and the rear U~joint.
The main objective of this section is to correct the
conditions that interfere with the proper cancellation
effect of the U~joint. The most common condition,
especially where the launch shudder is concerned, is
in.correct driveline working angles (1,2). Other
factors may aggravate the condition.