18NA358

Bulletin No.:
Service Bulletin
Date:
18-NA-358
October, 2020
TECHNICAL
Subject:
Shudder, 2-3 Upshift or 3-2 Downshift Concern
Model Year:
Brand:
Model:
from
Enclave
Buick
LaCrosse
2014
Regal
SRX
Cadillac
Chevrolet
GMC
XTS
2014
VIN:
to
from
to
Engine:
Transmission:
(6T70, 6T75
or 6T80
Automatic)
2017
M7V, M7X
2016
M7U, M7W
2017
M7U, M7W
2016
M7U, M7W
2019
M7U, M7W,
M7V, MHM
—
—
—
Equinox
2017
Impala
2019
M7W
2015
M7W
Traverse
2017
M7V, M7X
Acadia
2019
M7V, M7X
2017
M7U, M7W
Malibu
Terrain
2014
2014
M7U, M7W
Involved Region or Country
North America, Europe, Russia, Middle East, Iraq, Israel, Palestine, Argentina, Brazil,
Chile, Colombia, Ecuador, Paraguay, Peru, Uruguay, Japan, Cadillac Korea, GM Korea
Company, Thailand, Egypt, Africa
Condition
Some customers may comment that the vehicle may have a severe launch shudder in 1st
gear from a stop, or while driving along when in 4th gear, or during the 2-3 upshift or 3-2
downshift.
Some customers may also comment on one or more of the following conditions:
• Flare
• Slide/bump
• Slip
• Harsh shift
Cause
This condition may be caused by debris in the upper and/or lower valve bodies or valve
scratched or scored, causing them not to move properly.
Note: Launch shudder concern may be induced/duplicated by power braking in first gear,
but should only be attempted for 5 seconds or less to not cause any distress to the
1-2-3-4 clutch assembly.
Validate that the concern is not an engine misfire or engine driveability concern.
Confirm the shudder is not a torque converter clutch (TCC) shudder by monitoring TCC
slip when TCC is engaged during the event.
Note: TEHCM replacement has not been an effective repair for the above concern.
Correction
Copyright 2020 General Motors LLC. All Rights Reserved.
• If the concern is not isolated to be an engine misfire, driveability concern or TCC
shudder concern, DO NOT replace the TEHCM.
• If the shudder can be induced during a power braking event in first gear as shown in
the video, then both the lower and upper valve body assemblies should be replaced at
the same time.
Note: Inspect ISS and/or OSS for debris collecting as this would be a sign of an internal
component failure. If no debris is seen on the sensors but valves and/or bores are
scratched, check for final drive bearing failure.
Page 2
October, 2020
Bulletin No.: 18-NA-358
Service Procedure
Refer to Control Valve Lower Body and Upper Body Replacement in SI.
Parts Information
Causal
Part
Description
Part
Number
Qty
X
BODY, C/VLV
UPR (W/O
MANUAL VLV)
24281084
1
X
BODY, C/
VLV LWR
24257450
1
X
BODY KIT, C/VLV
24264343
1
N/A
FLUID, A/TRANS
(DEXRON VI)
(1QT/0.946
LITRES)
Refer to EPC
Warranty Information For vehicles
repaired under warranty, use:
Labor
Operation
Description
Labor Time
8463870
Control Valve Lower Body
and Upper Body
Replacement
Use
Published
Labor
Operation
Time
Version
5
Modified
Released November 30, 2018
March 11, 2019 – Corrected Acadia and Enclave Transmission RPOs.
October 17, 2019 – Added the 2019 Model Year to the Impala and Acadia models and
updated the Involved Region or Country section.
February 28, 2020 – Added the 2018 and 2019 Model Year and Transmission RPO MHM
to the XTS.
October 16, 2020 – Added the last Note to the Correction section.
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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