GMC chervolet camaro 1999 Service Manual page 69

· 0-66 Vibration Diagnosis and Correction
Checking Phasing of U-joint
Inspect the propeller shaft for correct phasing. Correct
phasing means that the front and the rear U~joint
are directly in line or parallel with each other so that
proper cancellation takes place.
182316
1. Rotate the propeller shaft so that the propeller
shaft rear U-joint bearing cap is vertical.
182325
2. Ensure that the front bearing cap is also vertical.
3. Place the inclinometer on the propeller shaft
rear U-joint bearing cap in order to ensure
that both U-joints are vertical.
4. Set the indicator line above the sight glass on 15
(the horizontal reference). Rotate the propeller
shaft until the bubble centers in the sight
glass. This action brings the rear U-joint to vertical.
5. Remove the inclinometer without disturbing
the setting. Leave the setting on 15.
6. Install the inclinometer on the front U-joint. The
bubble should remain centered plus or minus
3 degrees if the shaft is properly phased.
General Information
The out of phasing of the single-piece propeller shaft
is very unusual. If the shaft is visibly out of place,
the end yokes are welded on in the wrong position or
the shaft is damaged due to twisting. In either
case, replace the propeller shaft before continuing
with this procedure.
Measuring the Working Angles
182180
The working angle of a U-joint is the difference
between the angles formed when two shafts intersect. (
One piece propeller shaft systems have two working
angles, the front (1) and the rear (2).
• The two working angles should be equal within V2
of a degree.
• The working angles should not exceed 4 degree$.
• The working angles should not be equal to
ZERO because a ZERO working angle will cause
premature U-joint wear due to lack of rotation
of the U-joint.
• The angle formed by the propeller shaft and the
rear axle pinion from the rear working angle (2)
• The angle formed by the propeller shaft and the
transmission output shaft form the front working
angle (1)
The angles of these components are most accurately
measured from the U-joint bearing caps. Verify
that the bearing caps are free of corrosion or foreign
material in order to ensure accurate readings. Remove
any snap rings that may interfere with the correct
placement of the inclinometer. Reinstall the snap rings
after you take the measurements.
Take the measurements from the same side of the
propeller shaft in order to maintain consistent
angle measurements (either on the driver side or on
the passenger side).