Service Bulletin

Bulletin No.:

18-NA-268

Date:

June, 2019

TECHNICAL
Subject:

Rattle Noise Heard from Front of Vehicle When Engine is Running at Slower Speeds

Brand:

Model:

Chevrolet

Corvette

Model Year:

VIN:

from

to

2014

2019

from

to

Engine:

Transmission:

6.2L (LT1, LT4)

6L80, 8L90
Automatic
(MYC, M5U)

Involved Region or Country

North America and N.A. Export Regions

Condition

Some customers may comment that they hear a rattle noise coming from the front of the
vehicle when the engine is running at slower engine speeds.

Cause

This condition may be caused by a deformed propshaft rubber coupler, which may move
the driveline support assembly’s front input shaft bearing out of position.

Correction

Note: Do Not replace the Driveline Support Assembly (DSA) for a recessed bearing.
Replacing the complete DSA will no longer be recommended.
If a noise was confirmed to be coming from the rear of the engine area, perform the
following steps in the Service Procedure below.

Service Procedure
1. Raise the vehicle.
2. Remove the engine’s bellhousing rubber
inspection plug.

Copyright 2019 General Motors LLC. All Rights Reserved.

Page 2

June, 2019

Bulletin No.: 18-NA-268

5315085

3. Inspect that the front bearing/slinger is flush (A)
with the housing:
⇒ If the bearing/slinger has been validated to be
the cause of the noise and/or found to be
pushed rearward more than ¼ inch (6 mm) (B),
continue with Propshaft Replacement
procedure in SI.

5300907

Note: Add medium strength thread locker to the DSA
flex plate clamp pinch bolt.
4. Verify that the propshaft hub clamp bolt is properly
torqued.

5. Inspect the flex plate:
• If an LT1 flex plate is installed (A), it is crucial
that the LT4 flex plate (B) be installed.
⇒ If the bearing/slinger is found to be pushed
rearward more than ¼ inch (6 mm), continue with
Propshaft Replacement procedure in SI.
• If the LT4 flex plate is installed, but the bearing/
slinger is pushed rearward, continue to the
next step.

Bulletin No.: 18-NA-268

June, 2019

Important: When installing a repaired driveline
support assembly, please follow all the installation
procedures in SI. Failure to follow the steps may lead to
premature crankshaft thrust bearing failures.
6. Remove the DSA. Refer to Driveline Support
Assembly Replacement in SI.
7. Remove the propshaft from the DSA. Refer to
Propshaft Replacement in SI.
8. Inspect the rubber coupler for damage.
9. If required, replace the flex plate.
10. Inspect and document engine crankshaft endplay:
• If the crankshaft endplay measurement
exceeds the specification, the crankshaft thrust
bearing should be inspected.
⇒ Crankshaft endplay should be measured and
documented on the repair order. Refer to Document
ID# 3746499 for specifications.
• If the crankshaft endplay is within
specifications, continue to the next step.
11. Install the propshaft into the DSA.
12. Install the DSA.
13. Lower the vehicle.
14. Take the vehicle for a test drive to validate if the
concern has been eliminated.

Page 3

Parts Information
Causal
Part

Description

Part
Number

Qty

X

PLATE, A/
TRNS FLEX

12669243

1

X

SHAFT, PROP

23366290

1

Warranty Information
Note: Only select the Labor Operation that coincides
with the repair performed.
For vehicles repaired under the Powertrain coverage,
use the following labor operation. Reference the
Applicable Warranties section of Investigate Vehicle
History (IVH) for coverage information.
Labor
Operation

Description

Labor Time

4086918*

Driveline Support Assembly
Inspection

0.2 hr

Add

Prop Shaft Replacement

11.0 hrs

Add

Crankshaft Endplay
Inspection

0.2 hr

Add

Automatic Transmission
Flex Plate Replacement

0.2 hr

*This is a unique Labor Operation for Bulletin use only.

Version

3

Modified

Released August 30, 2018
May 06, 2019 – Updated the Subject/Condition, Service Procedures, Parts and Warranty
information.
June 19, 2019 – Added the LT4 Engine and MYC Transmission RPOs.

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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