Shake and/or Shudder During Light Throttle Acceleration Between 40 and 128 KM/H (25 and 80 MPH) at a Steady State – 2015-2021 Cadillac Chevrolet GMC

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Service Bulletin Bulletin No.: 19-NA-018
Date: August, 2021
TECHNICAL
Subject: Shake and/or Shudder During Light Throttle Acceleration Between 40 and 128 KM/H (25
and 80 MPH) at a Steady State
Attention: This bulletin only applies to Mexico and Export Regions outside of the U.S. and
Canada.
Brand: Model:
Model Year: VIN Breakpoint Engine:
(2.0L, 3.0L, 3.6L,
5.3L, 6.2L)
Transmission:
(8-Speed
from to from to Automatic)
Cadillac
ATS 2016 2019
— —
LGX, LTG,
LT4, LF4 M5N, M5U, M5T
CT6 2016 2018 LGX, LGW, LTG M5N, M5U
CTS 2016 2019 LGX, LTG,
LT4, LF4 M5N, M5U
Escalade
Models 2015 2017 L86 M5U
Chevrolet
Camaro
2016 2019 LGX, LTG M5T
2016 2018 LT1 M5U
Colorado
(VIN S, T) 2016 2021 LGZ M5T
Corvette 2015 2019 LT1, LT4 M5U
Silverado
Models 2015 2018 L83, L86, L8B M5U, M5X
GMC
Yukon
Models 2015 2017 L86 M5U
Canyon 2016 2021 LGZ M5T
Sierra
Models 2015 2018 L83, L86, L8B M5U, M5X
Involved Region or Country Mexico, Argentina, Brazil, Chile, Ecuador, Guatemala, Peru, Europe, Israel, Middle East,
China, Japan, GM Korea Company, Cadillac Korea (South Korea), Philippines, Thailand
Condition
Some customers may comment on any of the following conditions:
• A shake and/or shudder during light throttle acceleration between 40 and 128 km/h
(25 and 80 mph) steady state driving when transmission is not actively shifting gears.
• A shudder feeling that may be described as driving over rumble strips or rough
pavement.
• Shudder feeling is evident in both Drive and M7 MY15-16 & L7 MY17, MY18 and
MY19 mode.
Page 2 August, 2021 Bulletin No.: 19-NA-018
Diagnosis Instructions
To ensure TCC Shudder is diagnosed correctly, please
drive the following schedule on a smooth road with
transmission sump temperature between 122°F (50°C)
– 158°F (70°C).
Important: For some road conditions, it may be
required to apply the brake pedal and throttle
simultaneously to stay within desired gear, engine firing
mode, engine torque range, and engine/vehicle speed
ranges.
For Full Size Trucks/SUVs – Press and hold the
tow-haul mode button for 5 seconds to disable grade
braking to prevent downshifts during test.
Run the following tests for 3 operational modes:
A. Normal Operation (GDS2 for viewing only)
B. GDS2 Commanding TCC in Disabled Operation
(TCC Open)
C. GDS2 Commanding TCC in Enabled Operation
(TCC Locked)
Shudder Test
Refer to the table below for conditions pertaining to
specific applications. In each vehicle, constant throttle
input on a smooth grade is desirable. PicoScope
Measured Frequency is the approximate vibration
frequency where TCC Shudder can be found,
discussed in detail below.
Vehicle Information Shudder Test Conditions Picoscope
Make App Eng
Type
Eng
RPO
Trans
RPO
Gear Eng
Mode
(V4,
V6, V8)
Trans
Input
Speed
(rpm)
Vehicle
Speed
(mph)
Eng
Torque
(Nm)
Meas
Freq (+/-
2 Hz)
Cadillac CTS 6
CYL. NA
LGX M5N 8 V6 1100-
1500
42-55 100-250 23
Cadillac CTS 4 CYL.
Turbo
LTG M5N 8 V4 1100-
1500
42-55 100-250 23
Cadillac CTS-V 8 CYL.
SCHGD
LT4 M5U 8 V8 1000-
1500
42-62 200-375 28
Cadillac ATS 4
CYL. NA
LCV M5T 8 V4 1100-
1500
42-55 100-250 23
Cadillac ATS 6
CYL. NA
LGX M5N 8 V6 1100-
1500
42-55 100-250 23
Cadillac ATS 4 CYL.
Turbo
LTG M5N 8 V4 1100-
1500
42-55 100-250 23
Cadillac ATS-V 6 CYL.
Twin
Turbo
LF4 M5U 8 V6 1100-
1500
42-55 150-300 26
Cadillac CT6 6 CYL.
Twin
Turbo
LGW M5X 8 V6 1100-
1500
42-55 150-300 26
Cadillac CT6 6
CYL. NA
LGX M5N 8 V6 1100-
1500
42-55 100-250 23
Cadillac CT6 4 CYL.
Turbo
LTG M5N 8 V4 1100-
1500
42-55 100-250 23
Chevrolet Camaro 6
CYL. NA
LGX M5T 8 V6 1100-
1500
42-55 100-250 23
Chevrolet Camaro 4 CYL.
Turbo
LTG M5T 8 V4 1100-
1500
42-55 100-250 23
Chevrolet Camaro SS 8
CYL. NA
LT1 M5U 8 V4/V8 1000-
1,500
40-55 (V4)
100-200
/(V8)
175-375
28
Chevrolet Corvette 8
CYL. NA
LT1 M5U 8 V4 (Eco
Driving
Mode)
1000-
1800
40-80 125-250 28
Bulletin No.: 19-NA-018 August, 2021 Page 3
Vehicle Information Shudder Test Conditions Picoscope
Make App Eng
Type
Eng
RPO
Trans
RPO
Gear Eng
Mode
(V4,
V6, V8)
Trans
Input
Speed
(rpm)
Vehicle
Speed
(mph)
Eng
Torque
(Nm)
Meas
Freq (+/-
2 Hz)
Chevrolet Corvette
Z06
8 CYL.
SCHGD
LT4 M5U 8 V4 (Eco
Driving
Mode)
1000-
1800
40-80 125-250 28
Chevrolet/
GMC
Silverado/
Sierra
8
CYL. NA
L83 M5U 8 V8 1050-
1500
45-55 200-375 26
Chevrolet/
GMC
Silverado/
Sierra
8 CYL.
NA BAS
L8B M5X 8 V8 1050-
1500
45-55 200-375 26
Chevrolet/
GMC/
Cadillac
Silverado/
Sierra/
Yukon
Denali/
Denali XL/
Escalade/
ESV
8
CYL. NA
L86 M5U 8 V8 1050-
1500
45-55 200-375 26
Chevrolet/
GMC
Colorado/
Canyon
6
CYL. NA LGZ M5T 8 V6 1100–
1500 42–55 150–250 25
SCHGD = Supercharged
To confirm TCC Shudder, the vibration concern must be
created in normal operation (Mode A) of the test. If the
concern is gone with the torque converter clutch
disabled (Mode B, TCC Open) and is gone with torque
converter clutch enabled (Mode C, TCC Locked), then
the vibration root cause is TCC Shudder, and the fluid
flush procedure corrective action described below
should be performed.
If the concern is not present in Mode A, then the
vibration concern is NOT TCC shudder.
If the concern is still present with the torque converter
clutch disabled (Mode B) or with the torque converter
clutch enabled (Mode C, TCC slip speed at zero), then
the vibration root cause is NOT TCC Shudder.
Vibrations not identified as TCC Shudder should be
further investigated using the Vehicle Vibration
Diagnosis in SI as a starting point.
Picoscope Test
The PicoScope (CH-51450) essential tool and NVH
software or GDS must be used to confirm TCC
Shudder, Engine, Tire, or Driveline component related
conditions.
To confirm TCC Shudder, record the PicoScope data
while driving in 8th gear in the application specific
condition above. Minimize extraneous vibration input by
testing on a smooth road and correct any other known
vehicle vibration issues (tires, brakes, etc.) before
conducting test. If TCC Shudder is present, a vibration
peak will appear (highlighted by arrow below) within
+/-2 Hz of the frequency listed in the table above. TCC
Shudder vibration frequency is stationary in 8th gear. If
the vibration frequency follows vehicle speed or engine
speed, then it is NOT TCC Shudder.
4629472
In the above illustration, frequency and default view
have been selected.
Important: Obtain a screen print from GDS or PICO
Scope that shows the TCC shudder event. This screen
print must be attached to the Repair Order hard copy
for reference.
Page 4 August, 2021 Bulletin No.: 19-NA-018
Service Procedure
Fluid Exchange Procedure – Perform Triple
Drain and Fill
Important: This procedure must be followed as
published. The exchange process is required to obtain
proper level of new Synthetic LV ATF HP fluid.
Intermixing of other types of transmission fluid or
aftermarket additive packages will result in a low
concentration level of new fluid and will not provide
satisfactory results.
1. Raise the vehicle.
2. Remove the transmission oil pan and drain the
transmission fluid following Service Information
(SI) for the vehicle you are servicing.
3. Install the transmission oil pan.
4. Fill the transmission with 7 liters of Synthetic LV
ATF HP fluid following Service Information for your
vehicle.
5. Lower the vehicle keeping the wheels off the
ground and run the transmission through all 8
forward gears, reverse and neutral.
6. Repeat steps 2-5 for the 2nd drain and fill.
7. Repeat step 2- 3, clean the transmission oil pan
and magnet, repeat step 4, and steps 8.
8. Perform the fluid level set procedure:
8.1. Get the transmission fluid temperature to the
proper temperature outlined below.
8.2. Remove the DT-51190 fluid fill adapter and
DT-45096-31 TransFlow adapter.
8.3. Install the level set plug.
Tighten
Tighten the plug to 9Y(80 lb in).
The TCC shudder condition should be directional
improved immediately after the fluid exchange
procedure. It may take up to 200 miles for the TCC
shudder condition to be eliminated.
Fluid Level Check Procedure
This procedure checks both the transmission fluid level,
as well as the condition of the fluid itself. Since the
transmission on this vehicle is not equipped with a fill
tube and dipstick, a tube in the bottom pan is used to
set the fluid level.
Warning: The transmission fluid level must be
checked when the transmission fluid temperature
(TFT) is between 35–45°C (95–113°F). If the TFT is
not within this range, either idle or brake torque the
vehicle to raise the fluid temperature, or shut off the
vehicle to allow the fluid to cool as required. Setting
the fluid level with a TFT outside this range will
result in either an under or over-filled transmission.
TFT>45°C=under-filled, TFT<35°C=over-filled. An
under-filled transmission will cause premature
component wear or damage. An over-filled
transmission will cause fluid to discharge out the
vent tube, possibly causing a fire that may result in
serious bodily injury or severe vehicle damage,
fluid foaming, or pump cavitation.
Note: Silverado, Sierra, Yukon and Escalade Models
equipped with a thermal bypass valve, the transmission
fluid level should be checked only after the TFT has
reached or exceeded an operating temperature of 90°C
(194°F). Once the TFT has reached or exceeded 90°C
(194°F), then turn OFF the vehicle and allow the TFT to
cool back down to 35–45°C (95–113°F) before
checking the fluid level as required. Reaching or
exceeding an operating temperature of 90°C (194°F)
opens the bypass valve and allows the cooler to fill up
with fluid, which will result in a more accurate fluid level
check.
1. Observe the TFT using the driver information
center (DIC) or a scan tool.
2. Start and idle the engine.
3. Depress the brake pedal and move the shift lever
through each gear range. Pause for at least 3
seconds in each range. Move the shift lever back
to PARK. Ensure the engine RPM is low (500–
800 RPM).
4. Allow the engine to idle for at least 1 minute.
5. Raise the vehicle on a hoist.
Caution: THE ENGINE MUST BE RUNNING when the
trans oil level check plug is removed or excessive fluid
loss will occur, resulting in an under-filled condition. An
under-filled transmission will cause premature
component wear or damage.
⇒ The vehicle must be level, with the engine
running and the shift lever in the PARK range.
Note: Continue to monitor the TFT. If the TFT is not
within the specified values, reinstall the trans oil level
check plug and repeat the previous steps.
7. Remove the transmission oil level check plug (1)
from the transmission fluid pan. Allow any fluid to
drain.
• If the fluid is flowing as a steady stream, wait
until the fluid begins to drip.
• If no fluid comes out, add fluid until fluid drips
out. Refer to Transmission Fluid Fill Procedure
in SI.
8. Reinstall the transmission oil level check plug and
tighten to 9Y(80 lb in).
9. Inspect for external leaks. Refer to Fluid Leak
Diagnosis in SI.
Parts Information
Refer to the Electronic Parts Catalog (EPC) to
determine the proper part numbers for your specific
application.
Bulletin No.: 19-NA-018 August, 2021 Page 5
Warranty Information
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
8480838*
Flush and Drain Fluids for
Transmission Shake and/or
Shudder Repair
Submit
Actual
Clock Time
*This is a unique Labor Operation for bulletin use only.
Version 2
Modified
Released February 07, 2019
August 25, 2021 – Added the 2020-2021 Model Years to Chevrolet Colorado and GMC
Canyon and updated the Involved Region or Country section.

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