09-04-20-001G

Bulletin No.:
Service Bulletin
Date:
09-04-20-001G
May, 2022
INFORMATION
Subject:
Front Tire Chatter/Noise vs. Rear Differential Chatter
Models:
2006-2022 Chevrolet Corvette
2016-2022 Chevrolet Camaro
Attention: This bulletin also applies to any of the above models that may be Export from North
America vehicles.
This bulletin has been revised to add the 2020-2022 Model Years and remove Canadian
dealers VOD reference under Evaluation. Please discard Corporate Bulletin Number
09-04-20-001F.
The purpose of this bulletin is to address a chatter
noise during low speed tight turn conditions (i.e.
parking lot, driveway, etc.) primarily during cooler
ambient temperatures. The condition can be
experienced in all directions: right, left, forward,
reverse. The condition typically reduces or diminishes
when the vehicle warms up, but may be worse when
the pavement is wet.
Note: For the 2011-2013 model year, the Goodyear F1
tire, available on Corvette Grand Sports and Z06
models, has a significant tread design change. This
new design is more susceptible to tire chatter or hop
than the previous design.
This condition may be caused by two potential sources
of chatter:
• Front tire hop
• Rear differential chatter/noise
The following subjective evaluation will help identify the
correct source of the suspect noise.
Evaluation
Test Conditions/Location
• Vehicle condition: Condition typically occurs
following an extensive ambient soak of the
vehicle. A vehicle soak of at least eight hours
during cool outside ambient temperatures is
required prior to evaluation.
• Road surface: Clean (e.g. limited gravel), dry
asphalt or concrete surface with sufficient space
to complete two to three full vehicle turns at first
gear idle speed.
Copyright 2022 General Motors LLC. All Rights Reserved.
Important: Limit the evaluation to four full vehicle
circles.
1. With the engine running and the vehicle at rest,
turn the steering wheel in the direction of the
intended turns until full steering lock is achieved.
Allow the steering wheel to come off of full lock
position slightly to prevent power steering system
damage.
A hand position at the bottom of the steering wheel
(6 o’clock) assists in the evaluation, but is not
required.
2. Engage the clutch in first gear (manual
transmission) or release the brake and place the
shifter in Drive (automatic transmission). The
objectionable noise should be quickly detected
once the vehicle has made one to two circles.
3. With the vehicle moving in a tight circle and the
objectionable noise present, move the steering
wheel in ¼ turn increments away from the full lock
position. A maximum of ½ to ¾ turn from full lock
should be sufficient to determine the source.
4. With a hand at the 6 o'clock position as a reference
indicating full lock, move the steering wheel to the
3 or 9 o'clock position and hold briefly to evaluate
(two to three seconds). Continue turning from the 3
or 9 o'clock position to the 12 o'clock position and
re-evaluate (two to three seconds). Repeat if
necessary for a maximum of four complete vehicle
circles.
For more information evaluating this condition, U.S.
dealers should refer to the May 2010 Emerging Issues,
Course Number 10210.05 — What's Hot: Cars:
Corvette Vibration and Noise During Parking Lot
Maneuvers (available at www.gmtraining.com).
Page 2
May, 2022
Diagnosis
•
Front Tire Hop: The objectionable noise will
reduce in severity or cease during the turning
sequence immediately when the steering wheel is
turned (¼ steering turn will typically dramatically
reduce front tire chatter). In colder ambient
temperatures (<-18°C (20°F)), an additional ¼ turn
(total of ¾ turn) may be necessary to sufficiently
eliminate the front tire noise.
If the diagnosis indicates the issue is tire hop, the
condition is within the design criteria (normal
condition) of the vehicle.
Important: DO NOT attempt repairs or change the
differential fluid.
Inform the customer the noise is tire hop and is
caused by the large amount of tire scrubbing
across the pavement as the vehicle is turned.
• Rear Differential Chatter/Noise: At the ¼ and ½
turn stops the objectionable noise WILL NOT
reduce in severity (e.g. loud, volume) but may
reduce in frequency (e.g. time between chatter
events).
Bulletin No.: 09-04-20-001G
If the diagnosis indicates the differential is the
source of the noise, follow the instructions below:
Important: DO NOT add a friction modifier in
combination with DEXRON® LS fluid. The limited slip
and active handling features may be adversely
affected.
• 2005-2008 Models: Refer to the latest version
of Corporate Bulletin Number 07-04-20-002.
The service bulletin specifies to drain and fill,
only with DEXRON® LS Gear Oil (75W-90), P/
N 88862624 (in Canada, use 88862625) for
customer concerns of rear differential chatter.
Note: fluid used prior to is a synthetic 75W90
requiring 4-6 oz of friction modifier. DEXRON®
LS contains friction modifier which does not
require an additional additive.
• 2009 and later Models: At the start of
production for the 2009 model year,
DEXRON® LS Gear Oil (75W-90), P/N
88862624 (in Canada, use 88862625) was
implemented to address rear differential
chatter. Refer to Symptoms - Rear Drive Axle
in SI for further diagnosis.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a
job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.
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