Bulletin No.: 19-NA-091

June, 2019

Page 19

Trailering Systems
The available Advanced Trailering System (Silverado)
and ProGrade Trailering System (Sierra) offer
additional and new technologies. The in-vehicle
trailering system features an available total of 15
camera views (requires an installed accessory
camera), such as HD Surround Vision and other unique
views including a transparent trailer view feature to help
provide added confidence when towing and a hitch
view camera used when connecting the trailer to the
vehicle.

5324568

Sierra bed-view camera.

5303297

Transparent trailer camera view.

5324544

Silverado High Country with 5th wheel.

Trailering — Vehicle Weight Ratings
Curb Weight
Curb Weight is the weight of a vehicle without the
driver, passengers or cargo but including the maximum
capacity of fuel, oil, coolant and other items of standard
equipment.
5303357

Trailer hitch camera view.

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June, 2019

Gross Axle Weight Rating
Note: It is important to remember that a vehicle's
GAWR is not a measurement of how much weight
each axle is actually carrying at any given time. The
actual amount of weight each axle is carrying is the
gross axle weight or GAW.
A vehicle's Gross Axle Weight Rating (GAWR) is the
specific weight determined by the manufacturer to be
the maximum allowable weight that can be placed on
an individual axle. Front and rear axles have individual
GAWR. The GAWR is a weight limit for each of the
vehicle's axles which is determined by the
manufacturer. A vehicle's axles should never be loaded
beyond the manufacturer's listed GAWR. The GAWR
includes the weight of the vehicle, passengers, cargo
and trailer tongue weight (if equipped). All of this weight
is distributed between two axles.
Gross Combined Weight Rating
Note: It is important to remember that the GCWR is
not an actual measurement of the weight of a tow
vehicle and a trailer, but rather the combined
maximum weight limit that the manufacturer has set
for the two vehicles once attached.
A specific vehicle’s Gross Combined Weight Rating
(GCWR) is based on parameters established by
chassis manufacturers. The manufacturer makes an
assessment in accordance with SAE International test
protocols, determining maximum GCWR. Additionally,
the OEM runs stringent tests based on internal
requirements which may include testing total GCWR
braking capability using only the towing vehicle chassis
braking system. GCWR is the total weight of the truck
pulling the trailer and the trailer itself. The truck chassis
dictates proper GCWR for safe operation of the
combination truck and trailer. GCWR is the total
allowable weight of the completely loaded vehicle and
trailer including fuel, passengers, cargo, equipment,
and accessories. Do not exceed the GCWR for the
vehicle.
Gross Combined Weight Rating — Calculating
To check that the weight of the vehicle and trailer are
within the GCWR for the vehicle, follow these steps:
• Start with the "curb weight" from the trailering
information label.
• Add the weight of the trailer loaded with cargo and
ready for the trip.
• Add the weight of all passengers.
• Add the weight of all cargo in the vehicle.
• Add the weight of hitch hardware such as a draw
bar, ball, load equalizer bars and sway bars.
• Add the weight of any accessories or aftermarket
equipment added to the vehicle.
The resulting weight cannot exceed the GCWR of the
vehicle.
The gross combined weight can also be confirmed by
weighing the truck and trailer on a public scale. The
truck and trailer should be loaded for the trip with
passengers and cargo.

Bulletin No.: 19-NA-091

Gross Vehicle Weight
Gross Vehicle Weight (GVW) is the total weight of the
truck and payload at a point in time and will vary. The
GVW includes the vehicle’s listed curb weight, cargo,
equipment, trailer tongue weight (if equipped) and
passengers. Vehicle options, passengers, cargo, and
equipment reduce the maximum allowable tongue
weight the vehicle can carry, which also reduces the
maximum allowable trailer weight.
Gross Vehicle Weight Rating
Note: It is important to remember that the GVWR is
not a measurement of how much a vehicle actually
weighs. A vehicle's actual weight is the gross
vehicle weight, or GVW.
A truck’s Gross Vehicle Weight Rating (GVWR) is the
maximum weight rating established by the chassis
manufacturer. The OEM will determine the GVWR
based on test results and vehicle dynamic performance
to ensure a safe, reliable truck. Safety standards that
apply to braking, vehicle stability, and chassis
manufacturer internal standards for durability, dynamic
stability and handling can restrict GVWR to less than
the sum of the gross axle weight ratings (GAWR) for
that vehicle. The GVWR is calculated by adding the
vehicle’s listed curb weight, the weight of any optional
accessories, cargo, the trailer tongue weight (if
equipped) and passengers.

Transmission — 6-Speed 6L90
Automatic
Overview

5324137

The Hydra-Matic™ 6L90 6-speed — RPO MYD is a
fully automatic, rear-wheel drive, electronic-controlled
transmission. It consists primarily of a 4-element torque
converter, an integral fluid pump and converter
housing, a single and double planetary gear set, friction
and mechanical clutch assemblies, and a hydraulic
pressurization and control system. There are four

Bulletin No.: 19-NA-091

June, 2019

variants of the transmission, all based on torque
capacity. Architecture is common between the variants,
and component differences are primarily related to size.
Transmission General Description
The 6-speed 6L90 has a 4-element torque converter
that contains a pump, a turbine, a pressure plate
splined to the turbine, and a stator assembly. The
torque converter acts as a fluid coupling to smoothly
transmit power from the engine to the transmission. It
also hydraulically provides additional torque
multiplication when required. The pressure plate, when
applied, provides a mechanical direct drive coupling of
the engine to the transmission.
The planetary gear sets provide the 6 forward gear
ratios and reverse. Changing gear ratios is fully
automatic and is accomplished through the use of a
transmission control module (TCM) located inside the
transmission. The TCM receives and monitors various
electronic sensor inputs and uses this information to
shift the transmission at the optimum time.
The TCM commands shift solenoids and variable bleed
pressure control solenoids to control shift timing and
feel. The TCM also controls the apply and release of
the torque converter clutch which allows the engine to
deliver the maximum fuel efficiency without sacrificing
vehicle performance. All the solenoids, including the
TCM, are packaged into a self-contained control
solenoid valve assembly.
The hydraulic system primarily consists of a vane-type
pump, 2 control valve body assemblies, converter
housing and case. The pump maintains the working
pressures needed to stroke the clutch pistons that
apply or release the friction components. These friction
components, when applied or released, support the
automatic shifting qualities of the transmission.
The friction components used in this transmission
consist of 5 multiple disc clutches. The multiple disc
clutches combine with one mechanical sprag clutch to
deliver 7 different gear ratios, 6 forward and one
reverse, through the gear sets. The gear sets then
transfer torque through the output shaft.

Page 21

Transmission — 10-Speed 10L1000
Automatic
Notice: The all-new Allison® / General Motors
10-Speed Transmission can be Serviced at
Authorized Chevrolet and GMC Dealers.
Overview

5343851

Right Side

5343900

Left Side
The Allison® Branded 10-speed 10L1000 automatic
transmission — RPO MGM or MGU, manufactured by
General Motors, combines enhanced performance, fuel
economy, greater operational flexibility, and improved
driver comfort and control, with an industry-leading
reputation for uptime and reliability. Designed for
high-performance and low-maintenance, the 10-speed
coupled with the Duramax® 6.6L diesel engine
provides superior power delivery and productivity. The

Page 22

June, 2019

new transmission is tested and validated in partnership
with Allison® Transmission. Each transmission will
deliver its legendary quality and durability. The
Duramax® / Allison® powertrain standard axle ratio has
been reduced to 3.42:1, reducing engine speed,
enhancing refinement and efficiency. Duramax®
equipped vehicles with the 10-speed transmission are
available as 2WD or 4WD.
Transmission General Description
The transmission is a fully automatic, 10-speed,
rear-wheel drive electronically controlled transmission.
The ten speed ratios are generated using four simple
planetary gearsets, two brake clutches, and four
rotating clutches. The resultant on-axis transmission
architecture utilizes a squashed torque converter, an
off-axis pump and four close coupled gearsets. The
four rotating clutches have been located forward of the
gearsets to minimize the length of oil feeds which
provides for enhanced shift response. There are
different variants of the transmission, all based on
torque capacity. Architecture is common between the
variants, and component differences are primarily
related to size.
The transmission architecture features a case with an
integral bell housing for enhanced powertrain stiffness.
A unique pump drive design allows for off-axis
packaging very low in the transmission. The pump is a
variable vane type which effectively allows for two
pumps in the packaging size of one. This design and
packaging strategy not only enables low parasitic
losses and optimum priming capability but also
provides for ideal oil routing to the controls system, with
the pump located in the valve body itself. The
transmission control module (TCM) is externally
mounted, enabling packaging and powertrain
integration flexibility. The TCM utilizes three speed
sensor signals providing enhanced shift response and
accuracy. The transmission enables solid fuel
efficiency, superior performance and outstanding
vehicle safety.
The 4-element torque converter contains a pump, a
turbine, a pressure plate splined to the turbine, and a
stator assembly. The torque converter acts as a fluid
coupling to smoothly transmit power from the engine to
the transmission. It also hydraulically provides
additional torque multiplication when required. The
pressure plate, when applied, provides a mechanical
direct drive coupling of the engine to the transmission.
The planetary gear sets provide the 10 forward gear
ratios and reverse. The TCM receives and monitors
various electronic sensor inputs and uses this
information to shift the transmission at the
optimum time.
The hydraulic system primarily consists of an off-axis
gear-driven variable vane-type pump next to the valve
body, and 2 control valve body assemblies. The pump
maintains the working pressures needed to stroke the
clutch pistons that apply or release the friction
components. These friction components, when applied
or released, support the automatic shifting qualities of
the transmission.

Bulletin No.: 19-NA-091

The friction components used in this transmission
consist of 6 multiple disc clutches. The multiple disc
clutches deliver 11 different gear ratios, 10 forward and
one reverse, through the gear sets. The gear sets then
transfer torque through the output shaft.
Power Take-Off
An all new factory integrated, engine-driven Power
Take-Off (PTO) is available and eliminates the need for
an aftermarket unit. Exclusively offered with the
10-speed transmission on select diesel models, it’s the
first fully integrated PTO system in the HD truck
segment, with the PTO’s drive gear operated via chain
to direct engine power. And because it is engine-driven
rather than turbine-driven, the PTO can be used while
the vehicle is idling. A button inside the cab enables the
PTO, and a mode selector allows adjustment of load
and torque output.

Transfer Case — Autotrac 2-Speed
Overview
If equipped, the Autotrac 2-speed transfer case on
4WD models electronically controls “4 Auto” mode,
allowing the truck to seamlessly shift between 2WD
and 4WD based on road conditions.
Autotrac helps the driver to select the ideal 4WD mode,
depending on road conditions, using electronic controls
to make the process seamless. The Autotrac 2-speed
transfer case offers four transfer case modes, allowing
the driver to select the ideal mode for specific on-road
or off-road conditions. To select a mode, the driver will
either push a button or use a rotary knob (depending on
equipment) located on the instrument panel to the left
of the steering wheel.
Operation
The Magna Powertrain (MP) model 3025 — RPO NQH
is a 2-speed automatic, active transfer case (ATC). The
MP 3025 ATC provides 5 modes, Auto 4WD, 4HI, 4LO,
2HI and NEUTRAL (N). The Auto 4WD position allows
the capability of an active transfer case, which provides
the benefits of on-demand torque biasing wet clutch
and easy vehicle tuning through software calibrations.
The software calibrations allow more features such as
flexible adapt ready position and clutch preload torque
levels. The technology allows for vehicle speed
dependent clutch torque levels to enhance the
performance of the system. For example, the system is
calibrated to provide 0–5 lb-ft (0–6.78 Nm) of clutch
torque during low speed, low engine torque operation,
and predetermined higher torque for 25 mph (40 km/h)
and greater. This prevents crow-hop and binding at low
speeds and provides higher torque biases at higher
vehicle speeds, in order to enhance stability.

Bulletin No.: 19-NA-091

June, 2019
•

•

5326341

Typical view of Sierra AT4 Autotrac 2 controls.
• 2 Hi: For normal operation on paved roads where
there is no loss of traction, this mode allows the
vehicle to operate as 2WD to help save wear on
4WD components. When this mode is selected,
the front axle is disengaged and power is
distributed only to the rear axle.
• 4 Auto: If road conditions frequently vary
between high and low-traction areas, 4 Auto can
help automatically distribute torque to the front
axle by anticipating the need for additional
traction, helping to improve handling and control.
In this mode, the front axle is engaged but the
transfer case uses an electronically controlled
clutch to manage torque sent to each axle. The
transfer case automatically adjusts the clutch to
help provide improved traction, stability and
control.
• 4 Hi: High-range 4WD is designed to help
increase traction when driving over loose, slippery
or demanding terrain, such as off-road conditions,
deep sand or snow. This mode is NOT designed
for use on dry surfaces or roads with good
traction, so it is important to shift out of 4 Hi as
soon as road conditions improve.

Page 23
4 Low: Low-range 4WD engages gearing within
the transfer case to provide more torque to the
wheels for off-road driving, such as in deep sand,
mud or snow. In severe off-road scenarios, 4 Low
is designed to help give the driver more control of
the vehicle’s speed when crossing obstacles or
rocks, or climbing and descending steep grades.
This mode should NOT be utilized at speeds over
45 mph (72 km/h) and is NOT designed for use on
dry surfaces or roads with good traction.
Neutral: Additionally, the vehicle may include N,
which disengages the driveline to allow the truck
to be towed behind another vehicle (also known
as dinghy towing). Use this range ONLY when
the vehicle needs to be towed.

Page 24

June, 2019

Bulletin No.: 19-NA-091

Turbocharger System Description
Variable Vane Turbocharger Overview

4584300

Legend
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)

Turbine Housing
Lower Vane Ring
Vane Ring Assembly Spacer
Upper Vane Ring Assembly
Adjusting Ring Assembly
V-Band Nut
V-Band
Compressor Housing Bolt

The turbocharger increases engine power by pumping
compressed air into the combustion chambers, allowing
a greater quantity of fuel to combust at the optimal air/
fuel ratio. The turbine spins as exhaust gas flows out of
the engine and over the turbine blades, and turns the
compressor wheel at the other end of the turbine shaft,
pumping more air into the intake system. This is a
BorgWarner™ single stage, water cooled, variable
geometry turbocharger (VGT) capable of producing
220 kPa (31.9 psi) boost pressure.
The ECM communicates with the turbocharger vane
position actuator via the controller area network (CAN)
bus to control the turbocharger vanes. The smart
actuator incorporates a brushless motor and is
mounted on top of the turbocharger. It is connected to

(9)
(10)
(11)
(12)
(13)
(14)
(15)

Core Assembly
Linkage Assembly
Linkage Assembly Nut
Compressor Housing O-Ring
Actuator Nut
Compressor Housing
Actuator

the vanes by a linkage rod. The vanes are used to vary
the amount of boost pressure and can control the boost
pressure independent of engine speed. The vanes
mount to a unison ring which is rotated to change the
vane angle. The ECM will vary the vane angle which
adjusts the boost dependent upon the load
requirements of the engine.
When the actuator arm is in the vertical top rest position
the turbocharger vanes are fully open. When the
actuator arm is in the horizontal bottom of travel
position the turbocharger vanes are fully closed.
The turbocharger vanes are normally open when the
engine is not under load. However, the ECM will often
close the turbocharger vanes to create back pressure
to drive exhaust gas through the Exhaust Gas

Bulletin No.: 19-NA-091

June, 2019

Recirculation (EGR) valve as required. At extreme cold
temperatures, the ECM may close the vanes at low
load conditions in order to accelerate engine coolant
heating.
The turbocharger is also utilized as a component of the
exhaust brake system. Under certain conditions, the
ECM will automatically close the turbocharger vanes to
build back pressure in the exhaust, which reduces
engine speed and slows the vehicle without applying
the brakes.
During regeneration, the ECM will vary the
turbocharger vanes to assist with the exhaust system
warm-up, and to maintain proper engine exhaust
temperatures needed to properly regenerate the DPF.
Each time the ignition is turned OFF, the turbocharger
vane position actuator performs a learn procedure. The
actuator arm sweeps the turbocharger vanes from fully
open to fully closed to obtain a count value. This value
is compared to the previous value to ensure proper
vane position. Following the learn sweep the actuator
sweeps the vanes two more times to clean off
combustion soot.

Page 25

Upfitter Integration Group
Important: When adding non OE content to a
vehicle, contact the GM Upfitter Integration Group
for assistance if needed.
1. To visit the GM Upfitter Integration Group Home
Page, Go to: http://www.gmupfitter.com/
Scroll to the bottom of the page and click on:
Contact Us / Request Data
2. A request form will appear in a new window. To
request technical assistance from the GM Upfitter
Integration Group, complete and submit the form.

Special Tools
The following new tools were released for the
2020 Silverado / Sierra 2500HD and 3500HD pickup
trucks:

Special Tools — Tool Number and Description
Tool Number

Description

EN-52793

Front Crankshaft Seal Installer (6.6L L8T)

EN-52794

Rear Crankshaft Seal Installer (6.6L L8T)

Training Courses
Training Courses — Description — Number and Course Name
Description

Number and Course Name

New Model Launch

#10320.18H — 2020 Chevrolet Silverado and GMC Sierra
2500HD/3500HD New Model Launch (T1CXH Truck)

Automatic Transmission

#17041.85V — 10L1000 Allison Branded® HydraMatic™
Transmission

Version Information
Version

1

Modified

Released June 10, 2019

Page 26

June, 2019

Bulletin No.: 19-NA-091

Trademark Footnotes
ACDelco® is a registered trademark of General
Motors LLC
Allison® is a registered trademark of Allison
Transmission
Android™ is a trademark of Google LLC .
Android Auto™ is a trademark of Google LLC
Apple® is a registered trademark of Apple Inc.
Bluetooth® is a registered trademark Owned by
Bluetooth SIG, Inc.
BorgWarner™ is a Trademark of Borg-Warner
Corporation

CarPlay™ Software Feature is a trademark of
Apple Inc.
Duramax® is a registered trademark of General
Motors LLC (United States)
Duramax™ is a trademark of General Motors LLC
HydraMatic™ is a Trademark of General
Motors LLC
LTE™ is a trademark of the European
Telecommunications Standards Institute (ETSI)
OnStar® is a registered trademark of OnStar, LLC
Wi-Fi® is the registered trademark of the Wi-Fi
Alliance

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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