GMC chervolet camaro 1999 Service Manual page 71

0-68 Vibration Diagnosis and Correction
5. Rotate the propeller shaft 90 degrees and place
the inclinometer on the transmission output yoke
bearing cap. The bearing cap must be straight
up and down in order to obtain an accurate
measurement.
6. Center the bubble in the sight glass.
7. Record the measurement.
8. Subtract the smaller reading from the larger
reading in order to obtain the front U-joint
working angle.
The front angle is considered the odd U-joint
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because this angle does not have another joint to
provide cancellation. The rear working angle (6) and
the middle working angle (7) act as a pair of U-joints in
order to cancel each other out, as in the one-piece
propeller shaft systems. Because of this condition,
keep the working angle of the odd U-joint (8) at
or under
%
of a degree.
Keep the working angle of this odd joint to a minimum
so that there are not any great fluctuations in speed
that need to be canceled out. The front joint is used as
the odd joint because the front joint angle does not
change with suspension bounce, rebound, or axle
windup. For this reason, think of the front propeller
shaft of a two-piece system as an extension of
the transmission output shaft.
General Information
Two-Piece Propeller Shaft Phasing
The setup and measurement techniques are identical
to that of a the one-piece propeller shaft system.
First, test for proper phasing, using the following
procedure:
1. Turn the rear propeller shaft so that the rear
U-joint is straight up and down. Verify that the
front U-joint of the rear propeller shaft is also
straight up and down.
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2. Rotate the shafts 90 degrees so that the front
propeller shaft front U-joint is straight up and
down. Ensure that the front propeller shaft is also
straight up and down (actually part of the slip
yoke on the rear shaft).
If the two U-joint of the front propeller shaft are not in
this phase, the two halves of the propeller shaft
may have been assembled incorrectly.
Two-Piece Propeller Shaft Lateral Alignment
The procedure for lateral alignment of a two-piece
propeller shaft is used for launch shudder or any
second-order driveline vibrations. Adjust the lateral
alignment before you measure and adjust the driveline
angles.
1. Raise and suitably support the vehicle on a hoist.
Refer to Lifting and Jacking the Vehicle in
General Information.
2. Look down the front of the propeller shaft.
3. If the propeller shaft is not straight, or if the center
bearing support is off to one side, relocate the
center support bearing (2) in order to make
the propeller shaft assembly as straight as
possible. Ensure that you do not create a
(
ground-out condition against the exhaust or (
another component.