GMC chervolet camaro 1999 Service Manual page 58

General Information
Diagnosing First-Order Driveline Vibration
Diagnosis will be much easier once you have identified
a vibration as first-order of driveline rotation during
the road test. Next identify the exact area of the
vibration and take proper action.
In most cases, vibration may be reproduced in the
stall. In the stall the vibration may be better or worse
than that experienced during the road test.
The objective is to reduce the vibration to the lowest
point possible in the stall, then evaluate the results
during a road test. Many times, a vibration you were ·
. only able to reduce drastically in the stall will be
completely eliminated on the road.
The cause of first-order driveline vibration is usually
excessive runout or an imbalanced component.
The following procedure offers a systematic process of
elimination in order to determine which component
is at fault:
1. Raise the vehicle to curb height. Support the
vehicle on a hoist or heavy stands. Refer to
Lifting and Jacking the Vehicle in General
Information.
2. Remove the rear tires/wheels. Refer to Tire and
Wheel Removal and Installation (Wheel Removal)
in Tires and Wheels.
3. Inspect the propeller shaft. The propeller shaft
should be free of undercoating before continuing.
4. Inspect the propeller shaft and the U-joint for any
obvious dents or damage; Dents or damage
will
contribute to first-order driveline vibrations.
5. Start the engine.
6. Place the transmission in gear.
7. Run the vehicle up to the speed at which the
vibration was most severe.
8. Record whether the vibration was present, and at
what speed.
9. If the vibration is not present, refer to Antilock
Brakes System Sche.matic References.
10. If the vibration is present, determine which end of
the driveshaft is vibrating the most. Hold your
hand against the pinion nose and the transmission
tailshaft, or hold an EVA vibration sensor up to
each component.
Vibration Diagnosis and Correction 0-55
11. If the vehicle is equipped with a two-piece
propeller shaft, inspect the center support bearing
for vibration.
12. If the transmission tail is vibrating, touch the
transmission crossmember under the transmission
mount. If there is no vibration on the
crossmember, then the transmission mount is
working properly.
13. Remember which end of the driveshaft is the
worst, and how severe the vibration is. The
inspection will be a reference by which to judge
future progress.
Do not fill the propeller shaft with foam, oil, or any
other substance in order to correct a vibration. Filling
the propeller shaft is only effective in reducing an
unrelated condition called Torsional Rattle. Filling the
propeller shaft should only be done in strict
adherence to the procedure outlined in corporate
bulletins that address Torsional Rattle. Failure to follow
the correct procedure will induce a vibration and/or
affect the structural integrity of the propeller shaft. The
propeller shaft will then have to be replaced.
Propeller Shaft Runout
A propeller shaft or pinion (companion) flange with
excessive runout causes first-order driveline vibrations.
Use the following procedure in order to measure the
runout of the propeller shaft:
• Remove excess corrosion of the propeller shaft
surface before inspecting the runout.
• Inspect for damage and dents.
• Replace dented propeller shafts.
• Remove any undercoating from the propeller shaft
before proceeding.
• Refer to Measuring Propeller Shaft Runout, below,
for the measurement procedure that applies to the
following shaft assemblies:
- One-piece
- Two-piece
The splined end of a propeller shaft is critical to the
smooth operation of a two-piece propeller shaft. When
inspecting stub-shaft runout, ensure that the dial
indicator readings are accurate.