White Paper onPowertrain Spec’ingJanuary 2005
KENWORTH. The World’s Best.
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WHITE PAPER OVERVIEW
This Kenworth White Paper on Powertrain
Spec’ing was developed to provide useful
information and recommendations on the new
generation of heavy duty engines, transmissions,
cooling systems, and related technology to ensure
maximum performance, fuel economy and
minimum vehicle life cycle costs.
There are seven major areas covered in this
Kenworth White Paper:
• Cummins Engines—page 1
• Caterpillar Engines—page 3
• Engine Cooling Systems—page 6
• Spec’ing Considerations for Powertrain
Lubricants—page 7
• Automated and Automatic Transmissions—page 8
• Axles and Drivelines—page 10
• Suspensions and Traction Control Options—
page 13
CUMMINS ENGINES
Technology OverviewCummins emission technology uses cooled
Exhaust Gas Recirculation, or EGR. This process
takes a small amount of exhaust gas from the
exhaust manifold, sends it through a cooler
to reduce the temperature, and
then blends it with fresh
intake air before it goes
into the combustion
chamber. This added
exhaust gas helps
lower the combustion
temperatures and
reduces emissions
while maintaining
power and efficiency.
A key feature of Cummins’ new engines is the
Holset Variable Geometry (VG) turbo. This design
constantly adjusts airflow based on engine load,
fuel quantity, ambient pressure, temperature and
other conditions to provide the exact amount of
boost needed at any engine speed. This unique
design uses a
single sliding
nozzle with only
one moving part in
the exhaust
stream. The Holset
VG turbo is proven
technology and is
more reliable and
durable by design than other competitive designs
due to fewer moving parts.
Most truck owners will see no change from their
current preventive maintenance intervals,
including engine oil and filter changes. The
Cummins ISX is designed to operate between
service intervals in normal service use up to
25,000 miles.
PowerSpec ToolCummins PowerSpec is an application available
from the Internet that allows users to establish
feature and parameter settings, gearing
recommendations and basic trip and fault
information. By selecting an engine application
and answering a few simple questions, PowerSpec
will provide gearing recommendations specific to
the intended service. Users can enter specific
component options to determine what
combination of tires, transmission and rear axle
will optimize the vehicle performance. Kenworth
dealers can work with customers using PowerSpec
to create and load feature settings prior to
delivery of the vehicle to the customer.
The Cummins ISX is
designed to operate up to
25,000 miles between
service intervals in normal
service use.
Visit www.powerspec.cummins.com to download PowerSpec
and learn more about spec’ing Cummins engines.
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Key PowerSpec features and parameters include:
• Road Speed Governor Setting determines how
fast the vehicle travels on level ground to ensure
optimum fuel economy. As a rule of thumb, fuel
economy decreases by 1/10 mpg for every mile
per hour above 55 mph, primarily as a result of
higher aerodynamic drag.
• Idle Control sets the engine shutdown time and
adjusts idle speed control to improve fuel
economy during inactive operation. Heavy duty
engines typically use 0.5 gal/hr at 650 rpm and
1.0 gal/hr at 1,000 rpm.
• Gear Down Protection promotes increased fuel
economy by encouraging the vehicle driver to
operate as much as effectively possible in top
gear where fuel consumption is lower. This is
accomplished by limiting vehicle speed in lower
gears. Maximizing time in top gear means the
engine runs in a lower rpm range, thus
producing increased fuel economy and
improved durability.
• Engine Brake Settings allow the operator to
customize the brake application and operation
to best suit the driving conditions. These
options include the rate of brake application
and the vehicle speed range in which engine
braking is allowed.
Additional Cummins Features to AchieveMaximum Performance and Fuel EconomyIt is crucial to ensure that vehicles are spec’d
properly to balance fuel economy and
performance needs. PowerSpec, in conjunction
with the driver’s experience, will help optimize
the vehicle gearing to achieve these objectives.
Cummins SmartTorque (ST) rated engines help
drivers to drive smarter by providing up to 200 lb-
ft of extra torque in the top two gears. Using ST
promotes top gear usage resulting in a higher
percentage of time in top gear that translates into
improved fuel economy. This is accomplished by
allowing added peak torque under conditions
where it’s needed when in either of the top two
HOW IMPORTANT IS SPEC’ING TRANSMISSION ANDREAR-AXLE GEARING ON FUEL ECONOMY?
Based on Cummins testing, an engine geared to run 1,450
rpm at 65 mph gets approximately 4 percent better mpg
than one geared to run 1,600 rpm at 65 mph.
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gears. SmartTorque minimizes shifts, which
enhances fuel economy and driver satisfaction.
Load-Based Speed Control (LBSC) is Cummins’
engine management system that helps save on
fuel while providing power when needed. LBSC
works intelligently to understand the vehicle’s
operating conditions to balance performance and
fuel economy based on the Gross Vehicle Weight
(GVW) and grade. When maximum performance
is not required, LBSC manages the operating
range of the engine for maximum fuel efficiency.
LBSC also automatically ensures that the full
operating capability of the engine is available
when additional performance and operating
flexibility is needed, including:
• When driving in the top two gears
• When climbing grades
• When making gear changes
RoadRelay 4RoadRelay 4 gives drivers the means to increase
productivity by reducing idle time and improving
fuel economy, delivery performance and more.
The display provides
information while
they are driving to
help improve driving
habits and fuel economy.
Key features include:
• Trip and Route: Information is displayed and
recorded, including fuel, miles and engine
hours spent in idle, PTO and other operating
modes.
• Vehicle Protection: RoadRelay 4 constantly
monitors the powertrain. If an unexpected
event happens, RoadRelay 4 will inform the
driver and advise how to minimize potential
damage. It also tracks customizable service
intervals for oil changes, filter changes and tire
rotations, notifying the driver when it’s time to
head for the shop.
• Anti-theft: RoadRelay 4 comes with anti-theft
capability. This feature protects the vehicle from
theft when enabled.
CATERPILLAR ENGINES
Cat® Heavy-Duty ACERT™ OverviewCaterpillar has developed ACERT to provide
optimal combustion efficiency and produce
minimal emissions. The technology utilizes two
turbochargers in series, fuel systems, variable
valve actuation, and exhaust after-treatment.
Electronic controls manage the system.
ACERT uses a cross-flow cylinder head with four
valves per cylinder. To achieve high performance
and low emissions, the objective of ACERT is
twofold: get more clean air into the engine and
provide more uniform dispersion of that air
charge. ACERT uses proven turbochargers with
mechanical waste gates for increased
performance. Series turbochargers (two standard
turbos in series) provide the low-end response of a
small turbo with the higher-speed air volume and
boost pressures of a large turbo. Improved fuel
economy is an added benefit of this approach.
Maintaining optimized conditions requires that the
right amount of fuel be delivered at the right time
under the right pressure. Caterpillar engineers have
found that by providing multiple injections, they
can better control emissions. Managing these brief
events requires the world’s best injector technology
from Caterpillar—the Mechanically Actuated and
Electronically Controlled Unit Injection system.
This multiple-injection system is proven technology
based on millions of hours of successful real-
world experience.
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Variable valve actuation, controlled by electronics,
provides precise delivery of cooled air for
efficient, clean combustion. This technology
provides air delivery to meet varying engine
demands based on a wide range of factors, such as
coolant temperature, engine speed, throttle
position and more. Controlled by Cat advanced
electronics, this system allows just the right
amount of air for efficient and clean combustion.
This system also uses components from proven
Caterpillar technology. Benefits of variable valve
actuation include low emissions and improved
fuel economy.
Diesel oxidation catalyst after-treatment converts
hydrocarbons into carbon dioxide and water. The
process is fast, efficient and reliable.
Achieving Maximum Performance and FuelEconomy—CaterpillarCaterpillar has developed new guidelines for
gaining maximum fuel efficiency and
performance from ACERT engines, which may
differ from previous Caterpillar engines. As with
all engines, engine fuel consumption changes
when operated at different engine speeds.
Caterpillar’s recommendation to “gear fast, run
slow” still applies on all Cat® Heavy Duty engines.
For most applications, there are some differences
in Caterpillar ACERT drivetrain specs that should
be followed to achieve the best balance between
fuel economy and performance in a Kenworth
truck. In most cases, ACERT engines will be spec’d
at lower engine rpm than prior generations of
Caterpillar heavy duty engines.
ACERT ELECTRONIC PARAMETERSProgrammable electronic parameters are available
to ensure proper engine operation. Setting
parameters correctly will maximize fuel economy
and control engine life cycle costs. Parameters
such as Vehicle Speed Limit, Low and Intermediate
Gear Limits, High Cruise Control Speed Limit, Gear
SPEC’ING TIPS FROM KENWORTH FORCATERPILLAR ACERT ENGINES
• A transmission with “close steps” in the top gears can
provide a closer match to recommended engine speed.
Double-overdrive transmissions should be considered.
• A transmission that provides “automatic shifting” in the
top two gears will assist the driver in maintaining the
proper engine speed over moderate-grade road terrain.
• To achieve optimum fuel economy, use direct or overdrive
transmissions with Gear Down Protection to ensure that
cruising speed can only be reached in top gear.
• Spec multi-torque engines for applications requiring less
than 1,650 lb-ft torque. These ratings provide additional
torque in the top four gears. With the additional torque,
the truck will have greater ability to crest a hill without
downshifting to improve fuel economy, reduce engine
wear and increase driver satisfaction.
For most applications,
there are some differences
in Caterpillar ACERT
drivetrain specs that should
be followed to achieve the
best balance between fuel
economy and performance
in a Kenworth truck.
Caterpillar has developed
ACERT to provide optimal
combustion efficiency and
produce minimal emissions.
The technology utilizes two
turbochargers in series, fuel
systems, variable valve
actuation, and exhaust
after-treatment. Electronic
controls manage the system.
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Gross Combination Line-Haul Cruising Speed Engine Weight (lb) for Maximum Fuel Economy Comments
C7 < 50,000 60 mph
2,000 rpm
> 50,000 60 mph
2,200 rpm
C11 < 60,000 65 mph
1,450 rpm
C13 Non Multi-Torque and < 80,000 65 mph
C13 Multi-Torque 1,450 rpm
410 hp 1,450/1,650 lb-ft
C13 < 80,000 65 mph
Multi-Torque 1,325 rpm
430 hp 1,550/1,750 lb-ft
C15 ≤ 80,000 Less than 1,750 lb-ft
Non Multi-Torque 65 mph
1,400 rpm
1,750 lb-ft and above
65 mph
1,325 rpm
C15 ≤ 80,000 65 mph
Multi-Torque 435 hp 1,325 rpm
1,550/1,750 lb-ft
and 475 hp
1,650/1,850 lb-ft
VSL should be set to prevent excessive speed.
Vocational Cruise Speed: Rear-axle ratio may need to
be spec’d at higher engine rpm to meet gradeability
and startability guidelines.
Vocational Cruise Speed: Driveline may need to be
spec'd at higher engine rpm to meet gradeability and
startability guidelines.
Vocational Cruise Speed: Driveline may need to be
spec'd at higher engine rpm to meet gradeability and
startability guidelines.
Heavy Hauler Cruise Speed:
1,500–1,650 rpm
Vocational Cruise Speed: Driveline may need to be
spec'd at higher engine rpm to meet gradeability and
startability guidelines.
Vocational Cruise Speed: Driveline may need to be
spec'd at higher engine rpm to meet gradeability and
startability guidelines.
Spec’ing Guides for Caterpillar ACERT Engines. Caterpillar ACERT Gearing Recommendation.
Down Protection and Idle Control can be set
during the vehicle order or pre delivery process.
StartabilityStartability is the ability of the vehicle to pull
away from a dead stop on a grade. Depending on
vocation, Caterpillar recommends following these
startability performance guidelines:
• 10% Pickup and Delivery
• 14% Line-Haul
• 20% On-Off Highway
• 25% Off-Highway
GradeabilityAt peak torque rpm in top gear, Caterpillar
recommends a minimum gradeability
performance threshold of 1.8%. At cruise speed in
top gear, 1.0% gradeability is ideal to achieve
best performance.
Gearing Recommendations for CaterpillarACERT EnginesThe chart above provides some general guidelines
to consider when spec’ing Caterpillar ACERT
engines.
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The following example compares a typical Owner
Operator gearing comparison (80,000 lb GCWR
and less) with the new Caterpillar ACERT engines.
Caterpillar MessengerIn 2003, Caterpillar introduced a new driver
message display for monitoring engine
performance and
operating
information. CAT
Messenger
graphically displays
and records fuel
usage and average
miles per gallon to monitor individual
performance in achieving fuel economy goals.
Messenger can also be enabled to alert drivers to
preventive maintenance inspections and oil
changes. Messenger displays the codes, indicating
a potentially serious engine problem
automatically by displaying diagnostic codes, with
both a number and a brief text explanation.
Security features of Messenger provide the
capability to allow or prevent engine starting, or
to shut the engine down by entering a 4-character
password into the display when the engine is at
idle. Other information that can be stored and
displayed includes:
• Vehicle trip information, including average
vehicle speed
• Cruise control set speed
• Fuel economy and fuel used
• Power Take Off (PTO) engine rpm set speed,
operation time and fuel consumed
• Percent idle time, fuel consumed
• Fuel temperature to the engine
• Boost and oil pressure
• Coolant temperature
• Intake manifold temperature
ENGINE COOLING SYSTEMS
All Kenworth radiators
and charge-air-coolers
are designed to
optimize the
performance of the
vehicle horsepower and
torque requirements to
the vocation, especially
when running at full
throttle at low speeds for
extended periods of time
in high ambient
conditions. Kenworth uses five basic sizes of
cooling modules:
Kenworth now offers a High Performance Engine
Cooling Ring Shroud to provide additional cooling
capacity with high horsepower and/or gross
combination weight ratings at or above 80,000
pounds. The High Performance Engine Cooling
Ring Shroud is mounted to the engine and
reduces fan blade tip clearance to promote more
efficient airflow over the cooling module.
Extended Life CoolantExtended life coolants (ELC) are a popular option
which allow operators to run the latest generation
of heavy duty diesels to overhaul, with no
supplemental coolant additives or coolant
changes necessary.
Extended-life coolants offer cooling system
protection for up to 300,000 miles. ELC contains
no silicates, nitrates, borates, phosphates, amines,
or other abrasive dissolved solids that can
Cooling Module Size(square inches) Models
840 T300
950 W900S
1,200 T800, W900L, T2000 and T600
1,430 W900B, T800H
1,520 T800W
Pre-ACERT Cat Spec TypicalSpec Type Recommendation New Cat ACERT Spec
Engine Rating 550 hp 1,850 lb-ft 550 hp 1,850 lb-ft
Transmission RTLO 18913A RTLO 18913A
Rear-Axle Ratio 3.55 3.25
Tires 285/75R24.5 285/75R24.5
Cruising Speed 1,410 rpm at 65 mph 1,300 rpm at 65 mph
Gradeability at Cruise 2.0 1.7
Startability 1st Gear 29.3 25.9
Startability 2nd Gear 17.0 14.9
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contribute to water pump seal wear. It provides
long-term corrosion protection for all cooling
system metals, including copper, brass, steel, lead
solder, cast iron and aluminum. It also offers
exceptional protection against pitting for wet
sleeve cast iron cylinder liners in heavy duty
engines and eliminates the need for the addition
of traditional supplemental coolant additives
(SCAs). Unlike traditional coolants that require
SCAs at 12,000- to 20,000-mile intervals, long-life
coolant requires only one recharging with an
extender product at 150,000 miles.
SPEC’ING CONSIDERATIONS FORPOWERTRAIN LUBRICANTS
Engine Oil Specifications for LowEmission EnginesKenworth Truck Company and its supplier,
ChevronTexaco, have taken steps to ensure that
the new generation of engine oils is compatible
with engine manufacturer requirements for the
new engine emissions standards. In June 2003,
Kenworth manufacturing plants transitioned to a
new formulation of Delo 400 multigrade oil. This
new formulation was optimized to meet the
demands of Cummins EGR engines while at the
All Kenworth radiators and
charge-air-coolers are
designed to optimize the
performance of the vehicle
horsepower and torque
requirements to the
vocation, especially when
running at full throttle at
low speeds for extended
periods of time in high
ambient conditions.
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same time providing the highest level of
performance with Caterpillar ACERT engines.
Delo 400 multigrade provides excellent soot
control, acid neutralization capability, maximum
thermal stability, and wear control while
minimizing diesel engine piston deposits.
Synthetic Transmission and Axle LubricantsKenworth trucks come standard with factory-
filled synthetic lubricants. The products, which
include SAE 50 synthetic manual transmission
fluid, 75W-90 synthetic axle lubricants and the
optional 80W-140 synthetic axle lubricant, meet
the Dana/Eaton Roadranger® extended 750,000-
mile warranty and 500,000-mile extended
lubricant drain interval requirements.
Synthetic lubricants provide superior all-climate
performance. The high viscosity index, low pour
point and subzero fluid flow provide for easier
cold-weather shifting, less drag and less gear wear
because vital transmission parts are lubricated
quickly. Since it is highly stable when exposed to
severe heat, oxidation and shear conditions,
synthetic lubricants provide exceptional high-
temperature lubrication for extended drain
intervals.
Synthetic transmission and axle lubes also
provide several low costs of operation benefits.
They provide antiwear additive, as well as rust,
oxidation and corrosion inhibitors that protect
bearings and synchronizers, reduce component
wear and promote longer transmission and
lubricant life.
AUTOMATED AND AUTOMATICTRANSMISSIONS
Automated and automatic transmissions are a
growing trend in the
industry. There are two
primary types:
• Automatic
Transmissions
• Automated Manual
Transmissions
Automatic Transmissions from AllisonAutomatic transmissions use a torque converter in
lieu of a clutch. The torque converter can provide
strong starting power, especially on hills or in soft
terrain. The torque converter multiplies the
engine’s torque, so the first gear offers similar
ratio coverage as the first two or three gears of a
manual transmission. Another feature of
automatic transmission is no power
interruption between or during shifts,
which can provide better
acceleration, smoother ride and
reduced shock loading of the
drivetrain, compared to a
THE NEW FORMULATION FOR KENWORTH’SFACTORY FILL DELO 400 MULTI-GRADE MOTOR OILIS COMPATIBLE WITH OLDER ENGINES
Delo 400 multigrade heavy-duty motor oil provides out-
standing protection under both pre- and post-2002 EPA
standards. This product can also be used in EGR-equipped
engines from other diesel engine manufacturers as well as
in all pre- 2003 heavy-duty diesel engines. Packaged
product labels have been updated to reflect the new
Caterpillar ECF-1 claim and will appear in circulation
as older inventories are depleted.
KENWORTH TRUCKS COME STANDARD WITHSYNTHETIC TRANSMISSION LUBRICANTS TOPROVIDE PREMIUM VALUE
• Superior Lubrication for Less Friction and Drag
• Better Fuel Economy
• Reduced Vehicle Downtime
• Lower Maintenance Costs
Kenworth Truck Company
and its supplier,
ChevronTexaco, have taken
steps to ensure that the
new generation of engine
oils is compatible with
engine manufacturer
requirements for the new
engine emissions
standards.
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manual transmission. Electronic controls
continuously monitor engine rpm, load and
terrain to keep the vehicle operating at peak
performance and optimum fuel economy.
Automated Manual Transmissions fromEaton Corporation With an automated manual, electronic controls
and electromechanical actuators take the place of
the manual shift lever. Some versions, such as the
all new Eaton Fuller UltraShift™, require no
clutch pedal for starting or stopping the vehicle.
Shifting is fully automatic once the vehicle is in
motion and managed by an onboard computer
which can provide fast and smooth shifts. The
transmission electronic control unit calculates the
vehicle load and, depending on the throttle
position and other inputs, provides the best gear
selection for the situation.
Eaton’s Top2 feature with the Lightning
transmission is another form of an automated
SMART TRANSMISSION SPEC’ING TIP FOR FLEETS
The Eaton Convertible Transmission is an innovative life
cycle cost solution targeted at fleet customers. The base
transmission is a 13-speed, which is operated as a 9-speed
for the truck’s first life operation. At resale, the Convertible
Transmission can be easily upgraded to a 13-speed for
higher resale. An excellent feature of the Eaton Convertible
Transmission is that it is available with a Top2 feature. As
with other Top2 models, the top two gears shift automati-
cally. In a convertible transmission, this means that the
Top2 gears are from a 13-speed transmission, providing a
17 percent gear step. This step size is ideal for the narrow
fuel economy rpm window of some new technology engines.
As an added incentive, the Eaton Convertible transmission
comes standard with a 5-year / 500,000-mile warranty.
When converted to a 13-speed, there is an additional one-
year / 100,000-mile warranty included with the conversion
kit upgrade.
Automated and
automatic transmissions
are being recognized for
higher productivity and
driver satisfaction.
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manual transmission designed specifically for
pickup and delivery and over-the-road
applications. The Lightning Top2 feature can
eliminate up to 80% of the shifts on highway and
urban roads. When shifting between 9th and 10th
gears, this solenoid, which is electronically
controlled by the transmission ECU, initiates the
shifting. As the terrain or vehicle speed varies, the
Top2 shift logic in the electronic control unit
determines which of the top two gears is best and
automatically makes the shift at the right time for
optimum economy and performance.
Features, Advantages and Benefits ofAutomated Manual and AutomaticTransmissionsAutomated and automatic transmissions are being
recognized for higher productivity and driver
satisfaction. With automated shifting, the driver
can more easily utilize both hands on the steering
wheel and focus their concentration on traffic and
the road.
Other benefits of automated and automatic
transmissions include:
• Automatic or automated shifting controls
driveline shock in components such as the
clutch, yokes, driveshaft and drive axle
components.
• Electronic fault management features alert the
driver of problems and carry out an automatic
fault analysis.
• Resale values for trucks spec’d with automated
or automatic transmissions can command a
premium ranging from $2,500–$5,000
compared to a manual 10-speed, depending on
the vehicle condition and age.
AXLES AND DRIVELINES
When spec’ing a truck,
careful attention must
be paid to the drive
axle, driveline and rear
suspension in order to
optimize the truck’s
performance and,
ultimately, its
profitability. The drive axle is one of the most
critical components in a truck. Ensuring that the
axle is appropriately specified could mean the
difference between a good performing truck and a
breakdown. Before choosing the rear axle,
information about the truck specification and
application must be known to identify the right
axle for the job.
Axle Spec’ing ConsiderationsAssessing the intended service of the truck is
critical for axle selection. Duty cycles of the
vehicle must be considered, including annual
mileage, distance between starts and stops,
percent of load going versus returning, road
surface type and grades. As the duty cycle is
uniquely different for each intended service, the
application guidelines for any one axle will vary
as well. In addition, the details of the truck
specification must be known, such as gross axle
weight rating, gross combination weight, gross
vehicle weight, engine horsepower and torque,
and the desired rear-axle ratio. In a number of
cases, the transmission low-gear ratio and tire size
are also required to accurately determine the
appropriate axle.
As the duty cycle is uniquely
different for each intended
service, the application
guidelines for any one axle
will vary as well.
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An axle that may be suitable with a 600-
horsepower engine in a line-haul application may
not be approved for a pickup and delivery (P&D)
application with even less horsepower because the
duty cycle is more demanding due to the frequent
starting and stopping associated with P&D.
For example, let’s take a look at the Dana Spicer
Application guidelines for the DSH40 tandem
axle. In a line-haul application, the axle is
approved for 600 horsepower and 2,050 lb-ft of
torque with a GCW of 125,000 lbs. But in the P&D
application, the maximum allowable is 550
horsepower and 1,850 lb-ft of torque and a GCW of
only 90,000 lbs.
This is just one example of how a truck’s intended
service and application can impact the approval,
reliability and performance of the drive axle. It is
important to take the appropriate steps up front
in the truck spec’ing process to accurately identify
the intended service, application duty cycle and
drivetrain details. Doing so can help reduce the
potential for axle failure while also working to
optimize the performance of the drive axle in
terms of reliability, durability and weight
capacity. Your Kenworth dealer not only has access
to a powerful sales tool but can also work with the
Kenworth Application Engineering Department to
help spec the right axle to pull and support the
load, fine tune the driveline combination to
optimize performance and efficiency, answer
questions and offer spec’ing tips for your unique
truck application.
Double-Reduction AxlesConventional tandem axles achieve torque
multiplication by transferring torque through one
ring and pinion set. A double-reduction axle
transfers torque through a planetary or helical
gear set in the input carrier first and then
through the ring and pinion. By dividing the
torque multiplication between two gear sets
instead of just one, internal stresses on gears and
bearings are reduced. The result is an axle with
high resistance to shock loading and improved
vehicle startability, making it an ideal choice for
heavy-duty and off-highway applications.
Planetary Wheel End Reduction AxlesTypically used in mining, logging, oil field and
heavy-haul applications, planetary axles are the
choice for extreme heavy-duty and off-highway
applications requiring high gross weights. Similar
to a double-reduction axle, the planetary axle
achieves its torque multiplication with two gear
sets. However, instead of a gear set in the input
carrier, the planetary axle first transfers torque
through the ring and pinion and then through a
final planetary gear set in the wheel end. The
result is an axle with high tolerance for heavy
loads. Kenworth offers planetary axles with
GAWR’s ranging from 58,000 lbs up to 150,000 lbs
and GCW’s up to 1 million lbs. Traditionally,
planetary axles have been speed limited to 40–45
mph in order to avoid excessive heat buildup in
the planetary gear set, and this is largely true for
the axles in the high end of the capacity range.
However, Kenworth offers planetary axles with
GAWR’s ranging from 58,000 lbs to 70,000 lbs and
GCW’s up to 330,000 lbs that can operate at
highway speeds without exposure to overheating
of the planetary gear set. These axles make an
ideal choice for heavy-haul and prime-mover
applications that haul loaded at slow speed one
way and return home empty at highway speed.
Dual Range (Two-Speed) AxlesThere are applications that require a truck to not
only operate at normal highway speeds, but also
at very slow, steady speeds when pulling heavy
loads out of muddy job sites or maneuvering on
uneven terrain. A transmission with a wide ratio
coverage, such as an 18-speed, will often meet the
needs of most heavy-haul applications. But for
those who need extra reduction, a dual range axle
is an alternative to an auxiliary transmission that
deserves consideration. Dual range axles are based
upon the same technology used in double
reduction axles discussed previously. Like the
double reduction axle, the dual range axle utilizes
a planetary gear set in the input carrier to
compound the ratio of the ring and pinion. Unlike
the double reduction axle, the dual range axles
give the operator the capability to engage—via a
dash-mounted switch—the planetary gear set for
low-range slow-speed pulling, or disengage the
gear set for high-range highway operation.
Tridem Drive AxlesWhile not particularly suited for over-the-road
use, tridems offer a number of advantages for
truck applications that demand time and mileage
off the pavement, such as logging, oil field service
12and mining, to name a few. With three axles
instead of two, tridems allow more load to be
carried on the drive axles, providing more tractive
effort. Additionally, the tridem axle provides
greater floatation and improved mobility in loose
surfaces. This is achieved by distributing the drive-
axle load over a greater surface area than a
tandem axle. Tridem axles are available on
Kenworth trucks in capacities from 58,000 lbs up
to 105,000 lbs.
Front Drive Axle–4x4, 6x6, 8x6, 8x8ConfigurationsIf your application demands the ultimate in
traction, a front drive axle is likely to be the
solution. When a front drive axle is added to a
truck, there are a number of drivetrain and
chassis components that are affected as a result.
First, a transfer case must be added to power the
axle. Transfer cases are available in a variety of
torque capacities and configurations. Second, a
front drive axle requires that the chassis be raised
approximately nine inches to provide adequate
clearance between the engine oil pan and the axle
housing. This usually requires the addition of a
rear suspension subframe to level the chassis. A
final consideration is insuring that the front and
rear axles turn at or very close to the same speed.
The speed at which the axles turn can be altered
by the axle ratio and tire size. A good rule of
thumb when spec’ing a front drive axle is to
There are applications that
require a truck to not only
operate at normal highway
speeds, but also at very
slow, steady speeds when
pulling heavy loads out of
muddy job sites or
maneuvering on
uneven terrain.
13
ensure that the speed of the front and rear axles
are within 1% of each other. A truck that has
improper mismatch will encounter excessive tire
wear and potentially premature damage to
drivetrain components. Many truck
manufacturers outsource installation of front
drive axles to aftermarket up-fitters. The
Kenworth factory installs front drive axles to the
highest of engineering and manufacturing
standards and backs them with a Kenworth
factory warranty.
DrivelinesKenworth trucks are standard with the proven
Dana Spicer 10-Series driveline yet are also
available with the low-maintenance Dana Spicer
Life XL-Series. Featuring a lightweight design and
improved sealing technology, the first lube is not
required until three years or 350,000 miles for on-
highway applications.
While it may appear to be simple, the proper
installation of a driveline involves a careful
balance of drivetrain and chassis component
location combined with rigorous calculations to
ensure that drivetrain vibrations are minimized.
Variables in the chassis specification, such as the
engine, transmission, wheelbase, suspension, axle
and even tire size, contribute to driveline design.
Every Kenworth drivetrain is custom designed to
provide optimum performance and not only meet
but exceed the requirements of
driveline manufacturers.
SUSPENSIONS AND TRACTIONCONTROL OPTIONS
SuspensionsFor many years, air suspensions have been
regarded as strictly on-highway suspensions due
to their relatively low level of axle articulation
and propensity for getting stuck in off-road
conditions, leaving vocational duty to mechanical
walking-beam or spring-type suspensions. As
demand for smoother riding and better handling
trucks has been increasing over the years, so too
has the demand for air ride suspensions.
Kenworth, one of the pioneering companies in air
suspension technology, has continued
development of air suspensions since the
introduction of its proprietary AirGlide 100 in the
1970s.
Today Kenworth offers an extensive lineup of
proprietary air suspensions from its ultra
lightweight AG380 to its family of 8-bag air
suspensions, including the AG400, AG460
tandems and the AG690 tridem suspension. The
AG400/460/690 suspension family’s 8-bag design
yields a smooth, stable ride and features a
lightweight yet durable one-piece swaybar that
provides up to 6" of axle travel and allows for high
axle cross-articulation. Unlike competing air
suspension designs, the AG400/460/690
suspension does not use the axle housing as a
torsional member, improving the life of the axle.
The result is an air suspension that minimizes
stress in the frame and cross-members and
provides outstanding traction in off-highway
conditions. The Kenworth AG400, AG460 and
AG690 are excellent choices for a number of
on/off-highway applications, including logging
and heavy haul.
Inter-axle Differential LockKenworth provides the inter-axle differential lock
as a standard feature and also provides an option
that restricts use of this feature while the
transmission is in high range. When engaged
(locked), the differential is inoperable and the
available input torque is distributed to both axles,
ensuring the vehicle maintains traction. This
feature is typically used at slow operating speed to
minimize the potential differential damage to the
forward axle.
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Wheel Differential Cross-LockFor vocational trucks that traverse off-road
surfaces, Kenworth offers a wheel differential lock
(also known as a cross-lock) that, when engaged,
distributes the available torque to all wheels,
ensuring the power is delivered to keep the
vehicle moving.
Central Tire Inflation SystemDana Spicer Central Tire Inflation System (CTIS)
provides enhanced mobility through improved
flotation and traction by the adjustment of tire
pressures. In off-road vocational applications, CTIS
has grown in popularity as an effective alternative
to all-wheel drive, providing good off-road
performance with far less weight, cost and a lower
overall vehicle height. CTIS features operator-
controlled inflation and deflation of all the
vehicles’ tires based on terrain, speed and load.
Automatic Traction ControlAutomatic Traction Control (ATC) is an optional
feature of Kenworth’s Antilock Brake System (ABS).
When a difference in speeds between wheels
occurs during acceleration, the ATC is activated,
controlling wheel spin to provide improved
traction. Other features of ATC are noted above.
Feature Advantage and Benefit
Automatic Differential Braking Reduces potential of powering into a
jackknife caused by wheel overspin
during acceleration or in curves. Provides
primary control when drive wheels are
operating on different surfaces; when
one wheel spins, ATC momentarily
applies the brake on that wheel to gain
traction.
Electronic Engine Control If both wheels on the sensed axle are on a
poor-traction surface, ATC automatically
reduces engine power to attain optimum
tire-to-road traction.
ATC Light on Dashboard Indication of slippery road conditions.
Automatic Traction Control
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SUMMARY
Proper spec’ing of the vehicle’s powertrain is
crucial to achieve high productivity and low life
cycle costs. The Kenworth Dealer Network of
nearly 300 locations in the U.S. and Canada
provides assistance in selecting the optimum
powertrain for your application through a state-of-
the-art, Kenworth PROSPECTOR® vehicle spec’ing
system. Kenworth dealers are backed by the
World’s Best engineering organization, which can
provide a wide range of technical and
applications assistance.
Spec’ing Guidelines for Air Suspensions
Kenworth Air SuspensionAG380 AG400 AG460 AG690
Configuration Tandem Tandem Tandem Tridem
Ride Height 8.5" 9" 10.5" 10.5"
Rated Capacity 38,000 lbs. 40,000 lbs. 46,000 lbs. 69,000 lbs.
Axle Spacing 52" 52", 54" 52", 54", 60" 54"
Intended Service Line-haul Line-haul Line-haul Line-haul
Local P&D Local P&D Local P&D Local P&D
EMT/Rescue/Fire EMT/Rescue/Fire EMT/Rescue/Fire
Heavy Transport Heavy Transport Heavy Transport
Wrecker* Wrecker* Wrecker*
Crane/Picker* Crane/Picker* Crane/Picker*
Oil Well Servicing Oil Well Servicing Oil Well Servicing
Loggers Loggers Loggers
Agriculture* Agriculture* Agriculture*
Construction* Construction* Construction*
Snowplows Snowplows Snowplows
Dump Dump* Dump*
Body Type Van All except All except All except
Beverage Mixer Mixer Mixer
Tanker Refuse Refuse Refuse
Flatbed Roll Off* Roll Off* Roll Off*
Road Usage 95–100% A&B 90–100% A&B 90–100% A&B 90–100% A&B
≤5% C ≤10% C ≤10% C ≤10% C
≤0% D ≤0% D ≤0% D ≤3% D
* Review required by Kenworth Application Engineering.
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Drivetrain Spec’ing - General Recommendations
Electronic Minimum EnhancementEngine Minimum Gradeability* Minimum Traction
Intended Service Parameters Horsepower (Cat Only) Startability† Transmission Drive Axle Suspension Features
Line-haul 400 1.5%–18% at 14% 9-Spd 40K Air Traction
peak torque in top Convertible, Control
gear, 1% at cruise 10/13-Spd
in top gear
P & D 305 1.5%–18% at 10% Automatic and 21K - 40K Air or Traction
peak torque in top Automated; Leaf Spring Control
gear, 1% at cruise 10-Speed
in top gear Manual
Dump 350 1.5%–18% at 16%–20% 10/11/13/18-Spd 40K-46K Walking Wheel
peak torque in top Manual or Allison Thick Wall Beam Diff-locks
gear, 1% at cruise Automatic Housing
in top gear
Mixer 305 1.5%–18% at 16%–20% 11-Spd 40K-46K Walking Wheel
peak torque in top Manual or Allison Thick Wall Beam Diff-locks,
gear, 1% at cruise Automatic Housing CTIS, 6x6
in top gear
Logger 430 1.5%–18% at 16%–20% 13/15/18-Spd 40K-46K Air or Wheel
peak torque in top Thick Wall Walking Diff-locks
gear, 1% at cruise Housing Beam
in top gear
Refuse Packer / 400 1.5%–18% at 11-Spd 40K-46K Walking Wheel
Roll-Off peak torque in top Manual or Allison Thick Wall Beam Diff-locks
gear, 1% at cruise Automatic Housing
in top gear
Refuse Transfer 430 1.5%–18% at 15% 10/13/18-Speed 40K-46K Walking Wheel
peak torque in top Thick Wall Beam Diff-locks
gear, 1% at cruise Housing
in top gear
Construction 400 1.5%–18% at 16%–20% 10/11/13/18-Spd 40K-46K Air or Wheel
peak torque in top Manual or Allison Thick Wall Walking Diff-locks,
gear, 1% at cruise Automatic Housing Beam CTIS, 6x6
in top gear
Heavy Haul 475 1.5%–18% at 15% 18-Spd 46K - 52K Air or Wheel
110K - 140K peak torque in top Tandem, Walking Diff-locks,
gear, 1% at cruise 58K-78K Beam Traction
in top gear Tridem Control
Heavy Haul 500 1.5%–18% at 15% 18-Spd or 46K - 52K Air or Wheel
140K - 185K peak torque in top with Auxiliary Single or Walking Diff-locks,
gear, 1% at cruise Double Beam Traction
in top gear Reduction Control
Heavy Haul 550 1.5%–18% at 15% 18-Spd or Planetary Air or Wheel
185K peak torque in top Automatic Walking Diff-locks,
gear, 1% at cruise with Auxiliary Beam Traction
in top gear Control, 6x6
Multi-torque ratings;
Idle shutdown timer;
On/Off fan controller;
Gear down protection;
Driver reward;
Duty cycle monitor
Idle shutdown timer;
ON/OFF fan controller
Gear down protection;
Idle shutdown timer;
ON/OFF fan controller;
PTO parameters
ON/OFF fan controller;
PTO parameters
Gear down protection;
Idle shutdown timer;
ON/OFF fan controller;
PTO parameters
Gear down protection;
Idle shutdown timer;
ON/OFF fan controller;
PTO parameters
Gear down protection;
Idle shutdown timer;
ON/OFF fan controller;
PTO parameters
Gear down protection;
Idle shutdown timer;
ON/OFF fan controller;
PTO parameters
Gear down protection;
Idle shutdown timer;
ON/OFF fan controller;
PTO parameters
Gear down protection;
Idle shutdown timer;
ON/OFF fan controller;
PTO parameters
Gear down protection;
Idle shutdown timer;
ON/OFF fan controller;
PTO parameters
* In order to meet gradeability requirements, vocational cruise speed may need to be spec’d at higher engine rpm.
† Operation on rough, soft, poorly maintained or unimproved surfaces adds 3% to the above values.
J.D. Power and Associates 2004 Heavy Duty Truck StudySM. Study based on 1,596 responses from principal maintainers of heavy duty trucks. The Vocational truck segment is defi ned as heavy duty trucks operating in typically rugged business environments such as construction, specialized heavy hauling, sanitation/refuse, forestry, mining, or utility services. Also included in this segment are dump trucks, concrete mixers, cranes, and other related vehicles. www.jdpower.com. ISO 9001. © Kenworth Truck Company, A Division of PACCAR. For more information, please call or visit your local Kenworth dealer or go to www.kenworth.com.
KENWORTH.The World’s Best.
“Highest in Customer Satisfaction among Vocational Segment Class 8 Trucks.”
Kenworth sets the standard for customer satisfaction.
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