Service Bulletin

Bulletin No.:

23-NA-072

Date:

April, 2023

TECHNICAL
Subject:

Shudders or Shakes at Low Speeds
Model Year:

Brand:

Model:

Buick

Enclave

2019

Cadillac

XT5
XT6

2020

Chevrolet
GMC

Blazer
Traverse
Acadia

from

to

2023
2019
2020

VIN:
from

Engine:

Transmission:

LFY

M3W

LGX

M3W

LGX

M3V

to

LFY

M3V

LGX

M3W

Involved Region or Country

United States, Canada, Mexico, Europe, Kazakhstan, Uzbekistan, Russia, Middle East,
Israel, Palestine, Chile (West), Paraguay (West), Uruguay (West), Venezuela (West),
Other Central America, China - SGM, Taiwan , Thailand (ASEAN), Singapore,
Philippines, Australia/New Zealand, Other Africa

Condition

Some customers may comment on shudders or shakes at low speeds.

Cause

This condition may be caused by possible torque converter clutch (TCC) shudder on shift
and/or poor control.

Correction

Transmission fluid may be contaminated and/or torque converter damaged. Follow
diagnostics below to determine condition status or repair.

Diagnostic Tips
TCC Shudder: (Typically seen on 4th-5th
Upshift as ISS Oscillation)
Important: Service agents must comply with all
International, Federal, State, Provincial, and/or
Local laws applicable to the activities it performs
under this bulletin, including but not limited to
handling, deploying, preparing, classifying,
packaging, marking, labeling, and shipping
dangerous goods. In the event of a conflict between
the procedures set forth in this bulletin and the
laws that apply to your dealership, you must follow
those applicable laws.
Record GDS2 Session Log and look for ISS oscillation
when driveline disturbance occurs.
Diagnose by performing launch from 0 mph speed at
15-20% pedal up to 30 mph.
Condition present when TCC Slip less than 150rpm
maximum.

Copyright 2023 General Motors LLC. All Rights Reserved.

6325119

Page 2

April, 2023

Bulletin No.: 23-NA-072

Poor TCC Control: (Typically seen in higher
gear 8th-9th) Steady-State Torque (50-70kph)

Line Graph Set-up

6325121

1.
2.
3.
4.

Engine Speed
TCC Slip Speed
Engine Torque
ISS (Turbine Speed) will show oscillation

TCC

Shudder

ISS
(Peak-Peak)

Action

Comment

Normal

50 rpm
200 rpm

Replace
Torque
Converter

Degraded

ATF

6325122

Line Graph Set-up

Degradation has
occurred. Check
Fluid Condition
(Instructions
below “Fluid
Condition Check”)
Damaged

Hardware
damage has likely
occurred.

6325123

1. TCC Slip
2. Gear
3. Engine Torque
4. ATF Temp
5. ISS
Perform TCC slip control test within this procedure.
Compare service tool collected data results to normal,
degraded, and damaged operation.

Bulletin No.: 23-NA-072
TCC
SLIP

CONTROL TEST
RESULT

Figure
2
Normal

Below 20 RPM

April, 2023
TCC RPM
Slip Peak to
Peak, at
Steady
Throttle

ACTION

Page 3

Figure 1 Parameter Minimum and
Maximum Values

Do nothing

Figure
3

Degraded

Near 60
RPM repeating

ATF
Degradation
has
occurred.
Check Fluid
Condition
(Instructions
below “Fluid
Condition
Check”)

Figure
4

Damaged

Near 100
RPM- erratic

Hardware
damage has
likely
occurred.
Replace
Torque
Converter

TCC Slip Control Test

6325125

Figure 2 Parameter Normal Test Result

1.
2.
3.
4.

Utilize TIS2Web / GDS2 / MDI service tool
Select module diagnostics – TCM
Select TCC data for session log / data collection
Collect data between 89 and 113 km/h (30 and 50
mph) steady state / steady throttle with minimum
15 seconds.
5. For line graph evaluation, set parameter minimum
and maximum to values stated for comparison:
See Figure 1
6. Evaluate collected data with line graphs and
compare data to each figure below:
• Normal State: See Figure 2
• Degraded State: See Figure 3
• Damaged State: See Figure 4

6325126

Page 4

April, 2023

Bulletin No.: 23-NA-072

Figure 3 Parameter Degraded Test
Result

6325131

6325128

•
•

Figure 4 Parameter Damaged Test
Result
•

•

•

6325130

Fluid Condition Check
Important: If either shudder condition or slip control
observed to be normal than do not proceed with ATF
Inspection/Change or Torque Converter Replacement.

The fluid should be red or brown.
The fluid should be transparent so that objects or
writing can be seen through it. Sample #1 is an
example of acceptable fluid. Sample #2 is an
example of very dark fluid. Sample #3 is an
example of black fluid. Samples 1, 2, or 3 would
be acceptable to perform the fluid drain and fill if
sample does not also have one of the following
three conditions.
In addition to checking the fluid color and
transparency, the fluid should be checked for an
odor of burnt fluid. If the fluid is very dark (Sample
#2), black (Sample #3), and has a burnt odor it
would indicate clutch damage has occurred
internally in the transmission and it would need to
be removed from the vehicle and investigated.
Fluid that is cloudy or milky or appears to be
contaminated with water indicates engine coolant
or water contamination. Refer to the last version of
Service Bulletin 08-07-30-035 for testing and, if
confirmed, find the source of the coolant/water
and repair. Then follow service manual
instructions “engine coolant/water in transmission”
to repair the transmission.
Inspect the fluid for excessive metal particles or
other debris:
• A small amount of “friction” material is a
“normal” condition.
• A small amount of “metal” from the
manufacturing process is a “normal” condition.
This is observed as fine silver streaks floating
in the fluid.
• If large pieces and/or metal pieces are noted in
the fluid, or the fluid when rubbed between
fingers feels gritty/sandy, it would indicate
hardware damage has occurred internally in
the transmission and it would need to be
removed from the vehicle and investigated.

Bulletin No.: 23-NA-072

April, 2023

Other Known Normal Operation
Conditions
High Torque Locked Condition — If complaint exists
at engine torques >287Nm, where the measured TCC
Slip is ~0rpm, then this is operating as designed. In
order to protect the clutch, we must lock it up at these
higher engine torques. Commanding TCC Locked
should provide same performance as this condition.

Page 5

Please proceed with #PIP5601A: Vehicle Vibration
Diagnosis and TAC Requests for Assistance With
Vibration Related Complaints.

Correction
If confirmed to be a TCC shudder and/or Poor TCC
Control DEGRADED CONDITION while monitoring
performance using scan tool and the fluid condition
does not show clutch or hardware damage or water/
coolant contamination, please drain and refill the
transmission using DEXRON VI fluid as per SI
instructions.
Note: A minimum of 200 miles (322 km) needs to be
driven after the drain and fill to confirm the repair.
If confirmed to be a TCC shudder and/or Poor TCC
Control DAMAGED CONDITION while monitoring
performance using scan tool and the fluid condition
does not show clutch or hardware damage or water/
coolant contamination, please replace torque converter
per SI instructions.

6325132

Line Graph Set-up

6325134

1. Engine Speed
2. TCC Slip
3. Engine Torque
AFM Low Torque Operation — If vehicle is an LGX
engine and complaint exists at engine torques