GMC Chevrolet Camaro 1998 Service Manual page 89

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General Information
Runout and Balance Testing with the
Electronic Vibration Analyzer (EVA)
Ensure that the runout of the various driveline
components are within specifications. If the runouts
are within specifications, strobe balance the driveline.
The EVA is able to simplify the balancing process,
using the following procedure:
1 . Use the EVA in order to determine which end of
the propeller shaft has the most vibration.
2. Mark the end of the propeller shaft (1) that has
the most vibration at four points, 90 degrees
apart. Number the marks 1 through 4 (2).
3. Mount the EVA sensor onto the bottom of the
following components:
• The differential housing
• The center bearing support (for two-part
propeller shafts)
• The transmission tailshaft assembly
4. Position the sensor as close to the propeller shaft
as possible. Ensure that the UP side of the
sensor faces up. Ensure that the sensor is
horizontal.
5. Start the engine.
6. Turn off all engine accessories.
7. Place the transmission in gear.
8. Run the vehicle at the speed which causes the
most vibration in the propeller shaft.
9. Hook the timing light clip to the trigger wire.
10. Plug the vibration sensor into Input A of the EVA.
Input B does not have strobe light capability.
11. Verify that the predominant frequency on the EVA
display matches the frequency of the original
vibration. Use the strobe light only if the rotation
speed of the propeller shaft is the predominant
frequency.
12. The EV A displays a series of questions in order to
select the correct filter. Press YES in order to
select the desired filter. Ensure that the frequency
is in the middle of the filter range. Use the full
range only as a last resort.
13. The display shows the test frequency, the
amplitude and the filter range. The driveline
is balanced when the amplitude is near two. In
some cases a slightly higher amplitude will provide
adequate balance.
14. Point the timing light at the propeller shaft. The
strobe effect will appear to freeze the propeller
shaft. Note which of the numbered marks is at the
bottom of the propeller shaft, or the 6 o'clock
position. This position is the light spot.
15. Turn the engine off.
16. Install a weight directly on the light spot.
17. Start the engine.
18. Run the vehicle at peak vibration speed.
19. Strobe the propeller shaft again.
The propeller shaft is balanced if the strobe image is
erratic and the amplitude is near two.
Vibration Diagnosis and Correction 0-77
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