GMC chervolet camaro 1999 Service Manual page 73

0-70 Vibration Diagnosis and Correction
Transmission Shims
If a transmission requires shims, order the shims
through the parts distribution system.
Installing most shims will change the transmission
angle approximately V2 degree.
182364
When shimming transmissions, use a shim made from
steel stock at the necessary thickness. Ensure that
the shim contacts the full width of the area to be
shimmed. Do not use washers.
Engine Related Vibration
Engine vibration is usually due to one or more of the
following conditions:
• First-order engine imbalance
• Inherent engine firing sequence
• Inherent engine shaking forces
• Engine-driven accessories
Because these vibrations are engine-speed related,
they are also usually torque sensitive. These vibrations
may appear and disappear at different vehicle or
road speeds, but will always appear at the
same engine speed.
For example, if a customer states that a vibration is
present at 40 km/h (25 mph), 64 km/h (40 mph),
and again at 104 km/h (65 mph), and that the
symptoms of the vibration are similar at each of these
speeds, the vibration is probably engine-speed
related. Any disturbance or vibration that is present
during the following road tests would be considered
engine-speed related:
• The neutral run-up test
• The downshift test
• The brake torque test
Any vibration that is present during the neutral
coast-down test is not engine-speed related. The
engine-related vibrations covered in this diagnosis are
engine-speed sensitive only.
General Information
First;.Order Engine Imbalance
Notice: Proper flywheel installation requires carefully (
WALKING the flywheel onto the crankshaft and
stagger-tightening the bolts. Proper torque converter
to flywheel installation then requires gradually
WALKING the torque converter to be flush with the
flywheel, prior to installing the bolts. Do not draw the
torque converter to the flywheel with the bolts. If
these precautions are not followed, warping or bending
of the flywheel and/or damage to the transmission
torque converter may result.
Engine imbalance is a condition that exists when a
component that rotates at crankshaft speed is
either unbalanced or has excessive runout. In rare
cases, the crankshaft may be unbalanced. In any case,
balancing the component or correcting the runout
rnay reduce the disturbance to an acceptable level.
Symptoms
• Vehicle shake at speeds of 500-1200 RPM,
or 8-20 Hz
• Roughness and BOOM at speeds of
1200-3000 RPM, or 20-50 Hz
• Vibration usually detected during the neutral
run-up test
Isolating the Components
1. Perform the neutral run-up test, noting the RPM at
which the vibration is the worst, and the severity.
Refer to Road Test.
2. Inspect all powertrain mounts. Repair or replace
as needed.
3. Inspect for any bindings or ground-outs in the
.exhaust system.
4. Matchmark the torque converter and the flywheel.
5. Disconnect the torque converter from the
flywheel.
6. Tie up the converter, away from the flywheel.
7. Perform the neutral run-up test again.
• If the flywheel shows any wobble or lateral
runout, replace the flywheel. Refer to
Engine Flywheel Replacement in Engine
Mechanical - 3.8L or Engine Flywheel
Replacement in Engine Mechanical - 5.7L.
• Re-index the torque converter in three different
positions. If the disturbance still exists, replace
the torque converter.
8. If the vibration still exists, inspect the propeller
shaft runout.
9. If the vibration still exists, inspect the harmonic
balancer.
10. If the vibration still exists, the problem is related to
residual engine imbalance. Refer to the
procedure below.
(
(