Information on Transmission Adaptive Functions and Correcting Low Mileage Harsh Shifts, Slips, or Flares – 2015-2021 GM Passenger Cars and Trucks

SEOCONTENT-START

Service Bulletin Bulletin No.: 16-NA-019
Date: December, 2020
INFORMATION
Subject: Information on Transmission Adaptive Functions and Correcting Low Mileage Harsh
Shifts, Slips, or Flares
Brand: Model:
Model Year: VIN:
Engine: Transmission:
from to from to
Cadillac
GM Passenger Cars
and Trucks 2015 2021 — — All
Equipped with
8L90 and 8L45
Automatic
Transmission
(RPOs M5U, M5T,
M5N, M5X,
MQD, MQE)
Chevrolet
GMC
Involved Region or Country
North America, China, Saudi Arabia, Japan, Germany, Korea, Brazil, Thailand, Egypt,
Israel, Guatemala, Peru, Ecuador, Argentina, India, Colombia, Indonesia, Vietnam,
Uzbekistan, South Africa, Venezuela, Philippines, Albania, Kuwait
Condition
Some customers may comment on low mileage vehicles with an automatic transmission
that the shifting may feel too firm (harsh), slips, or flares. Customers should be advised
that the transmission makes use of an adaptive function that will help to refine the shift
feel while driving and improve shift quality.
Note: Low mileage would be considered vehicles that have approximately 8050 km
(5000 mi) or less or on vehicles that have had a valve body, clutch repair or transmission
replacement in the last approximate 8050 km (5000 mi) or less.
Correction
Important: Using Tis2Web, please check the ECM/
TCM Software/Calibrations against what is currently in
the vehicle and if the description of the update is
relevant to the customer concern, please perform the
update prior to proceeding with the learns below. By
completing the software/calibration update, the clutch
adapts will clear and thus a Service Fast Learn (SFL)
followed by Adaptive Learning may be needed to
further learn specific clutches if shift concern exists.
The following should be used to determine what steps
should be followed within this document. The 8-Speed
transmission utilizes a total of 5 clutches to obtain all
the ratios. Utilize the chart within this document to
determine which clutch may require additional adaptive
learning.
• If a valve body replacement, clutch repair/overhaul
or transmission replacement was required, reset
the adapts using Service Fast Learn. Evaluate the
shifts and further learn pressures and volumes if
required using the procedure below.
• If a customer has a specific shift concern, the
Service Fast Learn (SFL) should be skipped.
Complete the Adaptive Learn procedure to further
learn pressures and volumes for the specific shift
concern.
Note: The Adaptive Learn procedure should be used
on vehicles that have approximately 8050 km (5000 mi)
or less or on vehicles that have had a valve body, clutch
repair or transmission replacement in the last
approximate 8050 km (5000 mi) or less. Performing the
Adapt procedure on high mileage vehicles may improve
shift quality for a limited amount of time but the vehicle
will most likely return with the same symptoms.
Transmission Adaptive Functions
The Hydra-Matic® 8-Speed RWD transmission utilizes
a line pressure and volume control system during
upshifts to compensate for new transmission build
variation as well as the normal wear of transmission
components. The variation from new and normal wear
of the apply components within the transmission over
time can cause shift time (the time required to apply a
clutch) to be longer or shorter than desired.
In order to compensate for these changes, the
transmission control module (TCM) adjusts the
pressure commands to the various pressure control
(PC) solenoids to maintain the originally calibrated shift
timing. The automatic adjusting process is referred to
as “adaptive learning” and it is used to ensure
consistent shift feel plus increase transmission
durability.
Page 2 December, 2020 Bulletin No.: 16-NA-019
The TCM monitors the A/T input speed sensor (ISS)
and the A/T output speed sensor (OSS) during
commanded shifts to determine if a shift is occurring
too fast (harsh) or too slow (soft) and adjusts the
corresponding PC solenoid signal to maintain the set
shift feel. The purpose of the adapt function is to
automatically compensate the shift quality for the
various vehicle shift control systems. The adapt
function is a continuous process that will help to
maintain optimal shift quality throughout the life of the
vehicle.
How to Adapt Your Transmission
Transmission adapts can be reset and relearned on
most vehicles through GDS2 by using the Transmission
Service Fast Learn procedure. This procedure is
completed in the service stall and no vehicle driving is
required.
To complete the Transmission Service Fast Learn
procedure, enter GDS2 Diagnosis and navigate to:
• Module diagnostics
• Transmission Control Module
• Configuration / Reset Function
• Transmission Service Fast Learn
Transmission Service Fast Learn is the recommended
method to reset and relearn adapts. This procedure is
available on all 2015-2021 MY Trucks, Cars and SUVs
with 8L45 and 8L90 Automatic Transmissions (RPOs:
M5U, M5T, M5N, M5X, MQD, MQE).
When the Service Fast Learn is complete, perform a
test drive and note any soft or harsh shifts.
To improve these complaint shifts further, locate the
clutches that need to be learned in the following table
below, and perform the required learning procedure for
each clutch listed in the chart. Execute the steps below
with the vehicle warmed up on a smooth level road. The
driver may observe a brief pulse behavior or firm shift
feel while the transmission is optimizing the clutch learn
characteristics.
Note: The transmission fluid temperature must be
between 35°C (95°F) and 95°C (203°F). Drive the
vehicle under normal conditions until this temperature
range is achieved. If the temperature is outside of this
range, the clutches will not be learned.
To Correct The
Shift Feel
Learn These Clutches
Applying
Clutch
Releasing
Clutch
1–2 C4 C3
2–3 C3 C1
3–4 C5 C3
4–5 C3 C4
5–6 C4 C2
6–7 C1 C4
7–8 C4 C3
3–1 C1 C4
2–1 C3 C4
N-D C3 – Perform garage shift adaptive
learning
N-R C5 – Perform garage shift adaptive
learning
Power Downshifts Just perform the shifts and they will
adapt
Note: Ensure Service Bulletin #16-NA-411 or
#16-NA-412 has been completed on the 2015 -2016
Silverado, Sierra, Yukon and Escalade models before
performing this procedure.
Note: For the 2015 Corvette, use the latest version of
Service Bulletin #14-07-30-001.
Note: The following adaptive learning procedure
was developed to further learn clutch pressures
and volumes required for specific shifts. To
expedite the learning process, it is recommended
to utilize a road with minimal traffic volume that has
as smooth and level surface as possible.
Note: Within GDS2, a Transmission Service Fast
Learn Data page has been created to aid in performing
adaptive learn by showing throttle percentage, engine
speed, transmission fluid temperature, and gear
command.
Note: 2018-2021 Model Year vehicles show the clutch
learn status within GDS2. A Transmission Service Fast
Learn Data page has been created to aid in performing
adaptive learn by showing throttle percentage, engine
speed, transmission fluid temperature, and gear
command.
Bulletin No.: 16-NA-019 December, 2020 Page 3
To Learn C1 (For 6-7 or 3-1 Shift)
1. Pressure Learns:
Note: It is recommended to utilize a road with a speed
limit between of 48-72 km/h (30-45 mph) for this
procedure.
• Shift the transmission into 6th gear with the
PRNDM in the M position. Obtain an engine
speed between 1000 and 1600 engine rpm.
Maintain this condition for a total of about 8 km
(5 mi). Cruise control may be used and has
been found to result in faster learning of the
clutch values.
2. Volume Learns:
• Complete 15 light throttle 6-7 upshifts at
approximately 15% throttle to further learn C1.
To Learn C2 (For 6-5 Shift)
1. Pressure Learns:
Note: It is recommended to utilize a road with a speed
limit 64-72 km/h (40-45 mph) for this procedure.
• Perform 10 normal mode 6-5 coast down shifts
(zero/light brake) to learn the C2 Return Spring
pressure.
2. Volume Learns:
• Shift the transmission into 8th gear with the
PRNDM in the M position. Obtain an engine
speed between 1000 and 1750 rpm. Maintain
this condition for a total of about 8 km (5 mi).
Cruise control may be used and has been found
to result in faster learning of the clutch values.
To Learn C3 (For 2-3, 4-5, or N-D Shift)
Important: Application Specific Silverado & Sierra
e-Assist (RPO M5X) Trucks: To enable Adaptive
Learn on 8-7 Coast downs, a power on (~15% throttle
through the upshift) 7-8 upshift must be performed prior
to each downshift. This action enables torque converter
clutch (TCC) controlled slip on downshift to occur vs.
TCC unlocked, which occurs on normal downshifts and
disables Adaptive Learn. As a supplement, if the
previous procedure is unsuccessful using GDS TCC
Control Functions, TCC can be left enabled during 8-7
Coast downs to aid in learning C3 pressure.
1. Pressure Learns:
• Perform 10 normal mode 8-7 coast down shifts
(zero/light brake) to learn the C3 Return Spring.
2. Volume Learns:
• Complete 15 light throttle 2-3 upshifts at
approximately 15% throttle to further learn C3.
To Learn C4 (For 1-2, 5-6, or 7-8 Shift)
1. Pressure Learns:
Note: It is recommended to utilize a road with a speed
limit between of 64-72 km/h (40-45 mph) for this
procedure.
• Shift the transmission into 7th gear with the
PRNDM in the M position. Obtain an engine
speed between 1000 and 1750 rpm. Maintain
this condition for a total of about 8 km (5 mi).
Cruise control may be used and has been found
to result in faster learning of the clutch values.
Important: Application Specific Express & Savana
Vans Pressure Learns: Perform 10 normal mode 7-6
coast down shifts (zero/light brake) to learn the C4
Return Spring.
2. Volume Learns:
• Complete 15 light throttle 1-2 upshifts at
approximately 15% throttle to further learn C4.
To Learn C5 (For 3-4 or N-R Shift)
1. Pressure Learns:
Note: It is recommended to utilize a road within a
Business Park or similar area, where it is safe to drive
at very slow speeds of approximately 8-40 km/h
(5-25 mph).
• Shift the transmission into 3rd gear with the
PRNDM in the M position. Start a very slow
acceleration, starting at about 1000 rpm.
Maintain the slow acceleration until you reach
about 2500 rpm. Once you reach 2500 rpm,
slow back down to 1000 rpm and repeat the
slow acceleration up to 2500 rpm. Repeat this
10 times.
2. Volume Learns:
• Complete 15 light throttle 3-4 upshifts at
approximately 15% throttle to further learn C5.
Power Downshift Adaptive Learning
Starting with the vehicle operation in 8th gear, slowly
apply pressure to the accelerator pedal until downshift
occurs. Repeat as necessary in each gear (8, 7, 6, 5, 4,
3 and 2).
Note: This procedure will learn the off-going clutch
adapts for desired power downshift control.
Garage Shift Adaptive Learning (For N-D or N-R
Shift)
1. After above clutches are learned C3 –Drive and C5
– Reverse. With the vehicle at a stop, hold foot on
brake pedal and move the shifter from Neutral to
Drive and release the brake once in gear allowing
the vehicle to roll 5-10 feet or Neutral to Reverse
and release the brake once in gear allowing the
vehicle to roll 5-10 feet. Repeat as necessary until
desired shift quality is achieved.
Note: This procedure will learn the C13567 (C3-Drive)
and C45678R (C5 – Reverse) oncoming clutch adapts.
Page 4 December, 2020 Bulletin No.: 16-NA-019
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
8480318* Transmission Service Fast
Learn
Use Actual
Clock Time
*This is a unique Labor Operation for bulletin use only.
Version 6
Modified Released January 25, 2016
August 19, 2016 – Added the 2017 Model Year and updated information.
November 13, 2019 – Added the 2018 Model Year and a Warranty statement.
September 02, 2020 – Removed Buick from Models table, added the 2015 and 2019-
2021 Model Years, added RPO MQE, updated the Involved Region or Country section,
updated the two bullet items under Correction, added a Note to the Condition and
Correction sections and updated the Notes just below the Shift/Clutch table.
November 16, 2020 – Added RPO MQD and updated Description of Labor Operation.
December 01, 2020 – Changed Labor Operation Description back to previous
Description.

SEOCONTENT-END