GMC chevrolet camaro 2000 Service Manual page 77

0-66 Vibration Diagnosis and Correction
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.
Evaluation
The working angle is within tolerance, following the
rule that the working angle of an odd joint in a
two-piece joint system is 1/2 degree or less. Notice
that in each of the good examples the front working
angle (FWA) is 1/2 degree or less and is treated as a
separate joint. The middle working angle (MWA)
and the rear working angle (RWA) are subtracted. The
difference (DIFF) is 1/2 degree or less. The middle
and the rear joints may cancel each other. ·
Correcting Working Angles
In order to change the working angles, shim the
components up or down. Look closely at the existing
angles. Use the existing angles and the .shims in
order to achieve the correct working angles,
Compared to horizontal or true level, the components
located at the rear of the vehicle are usually lower than
the components located at the front of the vehicle. This
condition is called down in. the rear. If a component with
a down in the rear angle is shimmed up .at the rear, the
shim will bring the component closer to the horizontal
(zero). Alternately, if a component with a down in the
rear angle is shimmed down, the component will move
farther from the horizontal (zero).
Rear Axle Wind-Up
Rear axle wind-up may cause launch shudder even
when all of the working angles are within specifications.
Rear axle wind-up occurs when heavy torque during
acceleration causes the pinion nose to point upward. In
order to compensate for axle wind-up, tip the pinion
nose downward. Install the axle shims incrementally,
performing a road test after each shim. Add shims until
the road test indicates that the shudder is eliminated.
General Information
Rear Axle Shims
Wedge shims of different sizes are available through
the parts' system and independent suppliers for
the purpose of shimming the rear axle angle. Wedge
shims are available in 2, 3, and 4 degrees.
Caution: Never attempt to shim a rear axle using
anything except shims that are designed for
this purpose. Failure to do so will result in the
shims falling out and a loss of vehicle control and
that could cause personal injury.
1
182361
Install the shims (5) in order to increase or decrease
the angle of the rear axle pinion. Install the shims
between the leaf spring (3) and the spring seat (2).
Depending on the design of the suspension [leaf spring
on top or underneath the axle (1)], and the direction
of the desired change, install the shims with either the
thick side toward the front of the vehicle or toward
the rear of the vehicle.
Important: After installing the shims, ensure that the
U-bolt has two or three threads above the nut.
Ensure a.lso that the center bolt, located in the spring
seat, is long enough to seat in the locator hole .. If
these two conditions do not exist, use longer U-bolts
and center bolts. Longer U-bolts and center bolts
are available through local spring shops. . ·
(