Drivetrains

Drivetrains
Drivetrains
Transmission Systems . . . . . . . . . . . . . . . . . . . . 1
Manual transmissions
Automatic transmissions
Continuously variable transmissions (Xtronic CVT)
Overdrive
Transmission interlock
Drivetrain Configurations . . . . . . . . . . . . . . . . . . 4
Front-wheel drive
Rear-wheel drive
4-wheel drive (includes part-time, full-time,
and automatic)
All-wheel drive (AWD)
ATTESA E-TS
Dana axles
Limited-slip differential (VLSD, HLSD)
Locking rear differential
Limited Slip (ABLS)
Hill Descent Control (HDC)
Hill Start Assist (HSA)
Clutch start cancel switch
Traction Control System (TCS)
Vehicle Dynamic Control (VDC)
For Additional Information . . . . . . . . . . . . . . . . 10
Nissan/Infiniti manual transmissions consist of five or six
forward gears and one reverse gear that are engaged by
manually depressing the clutch and moving the shift lever.
Like a brake pad, the clutch contains friction material that
wears away every time the clutch slips due to overloading
or incorrect timing of acceleration and clutch pedal
release. Clutch hydraulic system parts and fluid are similar
to the brake hydraulic system and may also require
periodic service.
Manual transmissions employ synchronizers that allow
gears to mesh during shifting without grinding. Nissan
and Infiniti transmissions use double- or triple-cone
synchronizers on the gears that receive the most use
(generally 2nd and 3rd gears). Double-cone synchronizers
are two tapered rings, or collars, between the gears. They
serve as internal braking mechanisms that enable gears
rotating at different speeds to rotate at the same speed
during upshifts and downshifts. The use of two rings rather
than one allows the gears to mesh more smoothly and
enhances the durability of the transmission. Proper
selection and maintenance of manual transmission fluid also
allows smooth, quiet operation and enhances service life.
Transmission placement for rear-wheel-drive
configurations
Transmission
Driveshaft
TRANSMISSION SYSTEMS
The transmission manages the transfer of power from the
engine’s crankshaft to the driveshaft, which in turn sends it
on to the axles and wheels.
The transmission operates in a manner similar to a
bicycle’s rear wheel sprockets. Larger and smaller
sprockets create faster and slower speeds from the same
leg action. When the transmission shifts gears, it transfers
— and even multiplies — the power from the engine to the
driving wheels. Just as a bicyclist changes gears to match
the pedal effort with riding conditions, the transmission
changes gears to keep the engine operating in the most
efficient rpm range.
There are three types of transmissions:
• Manual transmissions
• Automatic transmissions
Longitudinally mounted engine
Rear differential
With rear-wheel-drive vehicles, the driveshaft carries the
power to a rear differential that then distributes the power
to the rear wheels. Rear axle lubricant must be properly
selected and periodically changed. Both manual
transmission and rear axle fluid should be changed more
frequently if the vehicle is used in severe service conditions
(such as towing a trailer). (See “Drivetrain Configurations”
in this chapter.)
• Continuously variable transmissions
Encyclopedia I 1
DRIVETRAINS
Traction and Stability Control . . . . . . . . . . . . . . 7
Manual transmissions
Transmission placement for front-wheel-drive
configurations
Transversely mounted engine and transaxle
With front-wheel-drive vehicles, there’s no separate
driveshaft or differential case. In their place is a transaxle,
which is a combination of the transmission and axle with the
clutch, gearbox, and differential gears integrated into a single
unit between the front wheels. It functions like a differential,
only the power doesn’t need to be transmitted through a long
driveshaft to the rear wheels. Transaxle fluid lubricates both
the transmission and differential sections of the assembly.
(See “Drivetrain Configurations” in this chapter.)
6-speed manual transmissions
Certain Nissan and Infiniti vehicles offer 6-speed manual
transmissions that are popular for performance-oriented
driving. They make it possible to keep the engine at or near
its torque peak during almost any driving situation. There
are two variations on the 6-speed design: “close-ratio” and
“wide-ratio.”
• A close-ratio design is similar to that used on many
racing cars. It generally means that there is less than a
25% difference between each successive gear ratio.
With this configuration, 1st through 4th are acceleration
gears; 5th gear is close to a 1:1 driveshaft-to-camshaft
turning ratio; and 6th is the overdrive or “cruising” gear.
• With the wide-ratio gearbox, 4th gear is nearly a 1:1
driveshaft to camshaft turning ratio, and both 5th and
6th gears are overdrive.
Nissan has developed a 6-speed manual transmission for
truck and SUV applications with a very low 1st-gear ratio
for enhanced off-road and towing capability. On 4x4
models, a clutch start cancel switch allows the driver to
start the vehicle without depressing the clutch, for use on
steep inclines in off-road conditions.
Automatic transmissions
Automatic transmissions offer increased convenience,
because they vary gearing automatically in response to
driving needs. Nissan/Infiniti automatic transmissions have
four or five forward gears, including an overdrive gear.
Most 5-speed automatic transmissions also have a manual
shift mode that provides a sportier shifting experience.
2 I Encyclopedia
Although the gears in an automatic transmission are
arranged differently, they perform the same function as in a
manual transmission. A combination of hydraulic and
electronic controls react to throttle position, engine output,
and road speed to select the correct gear. The automatic
transmission is filled with a special fluid that should be
checked and serviced per the maintenance schedule.
Lockup torque converter
All Nissan/Infiniti automatic transmissions have torque
converters. A torque converter is a hydraulic clutch that
transmits and multiplies engine torque while cushioning the
flow of power through the transmission components. A
lockup torque converter contains a special clutch that
engages at a preset speed to form a solid connection
between the engine output shaft and the transmission
input shaft. The locking effect created by this special
clutch reduces transmission friction. Reduced friction
increases fuel efficiency, while promoting longer-lasting
transmission parts. Also, because lockup torque
converters allow the engine to turn at a consistently lower
rpm, there is less cabin noise at highway speeds.
Electronically controlled
All current Nissan and Infiniti models have electronically
controlled automatic transmissions. Electronically controlled
automatic transmissions benefit from interaction between
the Engine Control Module (ECM) and the Transmission
Control Module (TCM). When the transmission is about to
shift, the ECM retards ignition timing momentarily to reduce
shift shock. The communication between the ECM and TCM
provides smooth, efficient shifting. It also increases the
service life of the transmission.
Nissan/Infiniti electronically controlled automatic
transmissions also feature a fail-safe mode that enables
them to function in a reduced capacity in case of electronic
malfunction, high transmission oil temperature, or low oil
level. A warning light on the instrument panel signals the
driver if the transmission goes into fail-safe mode. The
vehicle should not be driven long distances or at high
speeds in this condition, or further damage could occur.
Manual shift mode
The 5-speed automatic transmission with manual shift
mode allows you to change gears by moving the shift lever
forward to upshift or rearward to downshift. The driver can
stay involved with the way the car shifts gears. On certain
vehicles, Downshift Rev-Matching (DRM) raises engine
rpm momentarily to provide smoother downshifts and a
sportier feel, similar to “heel and toe” downshifting with a
manual transmission. (Note: When the gearshift lever is in
Drive, overdrive is engaged. When the lever is moved to
manual shift mode, however, overdrive is disengaged,
essentially downshifting into 4th gear.)
Continuously variable transmissions
(Xtronic CVT)
Pulley
Highstrength
steel
belt
Full-size truck and SUV transmission
The 5-speed automatic transmission available on Nissan
and Infiniti full-size vehicles is specially engineered to meet
the heavy-duty requirements of full-size vehicles. In
addition to providing high acceleration performance,
smooth shifting, and good fuel economy, it enhances the
ability to match gearing to driving conditions.
• Higher gear ratios help provide good fuel economy.
• Small step ratios (i.e. five speeds instead of four)
create smoother shifting.
• On most vehicles, a gated shifter provides a sportier look
and feel because it’s mounted in the center console, not
on the steering column like many other full-size vehicles.
• Its design provides precise control of gearshift
selection. The gated shifter allows drivers to choose
1st or 2nd gear, and 4th or 5th gear, by moving the
gearshift side to side. This is especially handy when
hauling or towing a heavy load.
• The transmission also has a standard tow mode that
revises the shift points to help reduce gear hunting
when driving under a load or when towing uphill.
Transmission oil cooler
The automatic transmission on all Nissan/Infiniti vehicles
has an oil cooler that maintains correct oil temperature
to preserve its lubricating qualities, enhancing the
transmission’s durability. It is especially useful for heavyduty operating conditions like towing, hauling a heavy load
at low speed, and during operation off-road. The
transmission oil cooler is either a separate external radiator,
or it is integrated into the lower half of the front radiator.
Automatic transmission fluid replacement
The 5-speed automatic transmission does not have a
traditional pullout dipstick for checking the automatic
transmission fluid level. Because the dipstick is bolted in
place, the transmission fluid level should be checked and
serviced at an authorized dealership. Also, only Nissan
Matic-J fluid can be used in the transmission.
How Xtronic CVT works
A continuously variable transmission transmits power by
means of two pulleys and a high-strength steel belt instead
of traditional gears. One pulley receives the power
generated by the engine and the other pulley transmits
drive power to the tires.
Both pulleys have V-shaped grooves in which the connecting
belt rides. One side of the pulley is fixed; the other side is
movable, actuated by a hydraulic cylinder. When actuated
by various sensors, the cylinder can increase or reduce the
amount of space between the two sides of the pulleys. This
allows the belt to ride lower or higher along the walls of the
pulleys, depending on driving conditions, thereby changing
the gear ratio. The gear ratio varies continuously rather
than in steps, like traditional transmissions.
Advantages
Xtronic CVT operates in much the same manner as a
conventional automatic transmission, with some key
differences.
• An automatic transmission typically has only four or
five fixed gear ratios to choose from, but Xtronic CVT
has an infinite number of ratios at its disposal. This
virtually eliminates the shift shock that occurs when
conventional automatic transmissions shift from one
gear to another. It also eliminates hunting for the right
gear when driving up a hill.
• When an automatic transmission shifts gears, engine
rpm rises above or falls below the engine’s optimum
power and efficiency range. Xtronic CVT continuously
adjusts the transmission’s output to keep the engine in
its optimum power and efficiency range at all times. This
means immediate acceleration for passing because
there’s no waiting for the transmission to downshift.
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DRIVETRAINS
• Lower gear ratios help provide good acceleration.
Nissan has been building Continuously Variable Transmissions
(CVTs) for more than a decade. In fact, today Nissan has
more than a million CVTs in operation worldwide. In North
America, Nissan introduced the advanced Xtronic CVT.
• Xtronic CVT is much more efficient at transferring
power from the engine to the drive-wheels because it
has fewer moving parts than a conventional automatic
transmission. Your customers get the best of both
worlds — the performance and fuel efficiency of a
manual transmission with the ease of use of an
automatic transmission.
Transversely mounted
engine and transaxle
Overdrive
All Nissan and Infiniti manual and automatic transmissions
are overdrive transmissions. That is, they have a specific
gear ratio that makes the engine’s crankshaft turn slower
than the driveshaft. For example, if the driveshaft were
turning at 3000 rpm in overdrive gear, the engine’s
crankshaft would be turning at less than 3000 rpm.
Because the engine can turn at a slower rate and still
maintain the same driveshaft speed, overdrive allows the
vehicle to operate more quietly and efficiently. The higher
gear ratio increases economy through better fuel efficiency
and reduced wear on the drivetrain. A slower-turning engine
promotes a more comfortable, quieter ride.
On many Nissan and Infiniti vehicles, a button on the
gearshift lever allows drivers to control the overdrive gear.
On vehicles with a gated console shifter, overdrive is
disengaged when the lever is moved from the Drive to the
4th or 3rd gear position. On vehicles with manual shift
mode, overdrive is disengaged when the manual shift
mode is selected.
Transmission interlock
All Nissan and Infiniti manual and automatic transmissions
have an interlock feature that helps prevent the
transmission from engaging accidentally. On vehicles
equipped with manual transmission, the interlock design
prevents starting the engine unless the clutch pedal is fully
depressed. On vehicles equipped with a conventional
automatic transmission or the Xtronic CVT (Continuously
Variable Transmission), the interlock design prevents
shifting from Park until the brake pedal is depressed.
dramatically raised the price of gasoline in the U.S. At that
time, automakers began to reduce the size of their
vehicles in order to improve fuel economy. But simply
reducing the size of existing vehicles created a serious
problem — a reduction in the interior size as well. In part,
this was due to the fact that conventional rear-wheel-drive
powertrain configurations intruded significantly into the
passenger compartment.
To solve the interior size problem, automakers adopted
front-wheel drive, which eliminates the longitudinal
driveshaft, rear axle, and large longitudinal transmission
hump. Vehicles with front-wheel drive also weigh less.
Nissan and Infiniti vehicles with front-wheel drive use a
transversely (side-to-side) mounted engine and a transaxle.
Advantages
• Front-wheel drive places more mass (weight) over the
front tires, which is an advantage when traction is
poor, such as in snow or other slippery conditions.
• It allows more interior room for a given size.
• It reduces the weight of the vehicle, which enhances
its power-to-weight ratio.
Rear-wheel drive
Longitudinally
mounted engine
Transmission
DRIVETRAIN CONFIGURATIONS
If the engine is the heart of a vehicle, the drivetrain is the
legs, because it transmits the engine’s power to the
wheels. There are four basic drivetrain configurations:
Driveshaft
• Front-wheel drive
• Rear-wheel drive
• 4-wheel drive (part-time, full-time, and automatic)
• All-wheel drive (AWD)
Rear
differential
Front-wheel drive
Front-wheel drive became popular in North America
during the early 1970s, when the first oil embargo
4 I Encyclopedia
Rear-wheel drive has become the preferred configuration
for performance vehicles, and it also allows trucks and
utility vehicles to carry and tow heavier loads. Nissan/Infiniti
vehicles with rear-wheel drive use a longitudinally (front-toback) mounted engine and transmission, with the
driveshaft connected to a rear differential, which transfers
power to the rear wheels.
and 4-wheel-drive high range when the vehicle is traveling
at speeds of up to 60 mph (“shift-on-the-fly”). The system
is electronically actuated, which simplifies engaging and
disengaging 4-wheel drive. A rotary switch on the dash
allows drivers to change modes.
Advantages
The system uses a 2-speed transfer case, with 4H (high
range) and 4LO (low range). The low-range gear provides
additional control during very low-speed operation, such
as for severe off-road conditions. In 4LO, throttle sensitivity
is reduced to allow better control in severe conditions. Due
to the low-range gearing, maximum speed in 4LO is limited
to 30 mph, and operating on dry pavement is not
recommended. 4LO can be engaged/disengaged only
when the vehicle is stationary and the transmission is in
Neutral or Park.
• The rear-wheel-drive layout distributes vehicle weight
more evenly than front-wheel drive, providing precise
handling and excellent driver feedback. (See also
“Front Midship (FM) platform” on page 50.)
• It provides a dynamic advantage by dividing steering
and power delivery functions between front and rear
wheels, rather than making the front wheels
responsible for both functions. Also, more braking
force can be applied to the rear wheels.
• Finally, there is no “torque steer” with rear-wheel drive.
With front-wheel drive, torque steer is the tendency for
a vehicle to pull in one direction under hard acceleration.
Engine
Transmission
Transfer case
Full-time 4-wheel drive
Axle
Driveshafts
With 4-wheel drive, the driveshaft transfers power to both
the front and rear wheels. A separate gearbox mounted
behind the transmission, called a transfer case, controls
whether power is directed to the front axle (4-wheel drive)
or just the rear axle (2-wheel drive). The transfer case also
can include an additional low-range gear for use at low
speeds over rough terrain.
There are three main types of 4-wheel-drive systems:
• Part-time 4-wheel drive
• Full-time 4-wheel drive
• Automatic 4-wheel drive
Part-time 4-wheel drive
Part-time 4-wheel drive allows drivers to choose manually
between 4-wheel drive for demanding conditions or rearwheel drive (2-wheel drive) for normal driving conditions.
The ability to choose 2-wheel drive for normal on-road
driving limits wear on drivetrain components, for reduced
maintenance costs.
Current Nissan vehicles with part-time 4-wheel drive have
a system that allows drivers to shift between 2-wheel drive
Full-time 4-wheel drive provides power to all four wheels at all
times, usually in a fixed front/rear proportion such as 50/50 or
38/62. Full-time 4-wheel-drive systems provide unnecessary
power constantly to all four wheels, which increases
steering effort and wear and also can affect fuel economy.
Currently, no Nissan or Infiniti vehicles offer true full-time
4-wheel drive because Nissan and Infiniti automatic
4-wheel-drive systems perform the same functions without
requiring driver intervention, and without incurring the wear
of a full-time system.
Automatic 4-wheel drive
To address the disadvantages of full-time 4-wheel drive,
certain Nissan and Infiniti vehicles offer a sophisticated
“automatic” 4-wheel-drive system that provides the
benefits of both part-time and full-time 4-wheel drive.
Automatic 4WD (All-Mode) is an advanced automatic
4-wheel-drive system and is easy to operate. When driving
on dry pavement (using the Auto mode), it directs power to
the rear axles only, for optimal fuel economy. The system
senses changes in surface conditions and instantly varies
the distribution of power between rear and front axles to
provide additional traction when needed.
Automatic 4WD provides four modes of operation:
• Auto mode is the very heart of the Automatic 4-wheeldrive system. It is the preferred and recommended
setting for all driving conditions.
Encyclopedia I 5
DRIVETRAINS
4-wheel drive
The previous-generation Frontier, Xterra, and Pathfinder
used a mechanically actuated 4-wheel system operated by
a transfer case lever. Frontier and Xterra used automatic
locking front hubs. After shifting from 4-wheel to 2-wheel
drive, drivers needed to back up approximately ten feet to
disengage (unlock) the hubs from their axles. Pathfinder
used permanently engaged hubs, which eliminated the
need to back up to disengage locking hubs.
Auto mode automatically and instantly provides a
50/50 front/rear power split for stable, no-slip start-ups
and varies power distribution between the front and
rear axles for improved driving stability under various
road conditions.
During normal dry-surface driving conditions, Auto
mode directs power only to the rear axle. However, if
road surface conditions deteriorate, it automatically
and instantly varies power distribution between the
front and rear axles — from 100% rear, to 50% rear
and 50% front, or any proportion in between.
Auto mode also enhances the operation of the Antilock Braking System (ABS), because it activates
additional front and rear driveshaft sensors that are
linked to the ABS Electronic Control Unit.
It’s important to point out to prospects that using the
Auto mode does not increase fuel consumption or tire
wear! It does provide an added level of control when
unexpected driving situations occur.
• 2WD directs 100% of the power to the rear axle for
driving on dry, paved roads. However, because the Auto
mode does the same thing, the 2WD mode is intended
mainly to facilitate “rolling road” emissions testing.
• 4H (Lock) mode directs an equal 50/50 power split
between the front and rear axles for operation on dirt
or severe road conditions.
• 4LO engages a super-low gear for use off-road and
provides additional control when very low-speed
operation is required. Throttle sensitivity is reduced to
allow better control in severe conditions.
Note: Beginning with 1999.5 QX4 and 2001 Pathfinder
LE, all controls for All-Mode 4WD are activated using a
single switch on the instrument panel. There’s no longer a
transfer case lever to engage 4LO.
To select 4LO in earlier QX4 models, stop the vehicle, set
the parking brake, place the automatic transmission in
Neutral, and move the transfer case lever firmly (without
hesitating) from 4H to 4LO. A 4LO symbol will illuminate to
confirm that 4LO is engaged. As with many 4WD vehicles,
leaving the transfer case in the Neutral position will allow
the vehicle to roll freely. Always use the parking brake
whenever shifting the transfer case or parking the vehicle.
If the transfer case lever is not completely shifted from High
to Low or from Low to High, the lever may stick in the
Neutral position. If this occurs, switch the engine off, move
the lever to the desired position, and restart the engine.
All-wheel drive (AWD)
Like automatic 4-wheel drive, AWD has the capability to
vary the amount of power directed to the front and rear
axles. However, AWD is intended primarily to enhance a
vehicle’s on-road, all-weather capability, as opposed to its
6 I Encyclopedia
ability to traverse difficult terrain off-road. AWD systems
are generally appropriate for light off-road use (such as
gravel or dirt roads), but they lack low-range gearing,
which limits off-road capability.
Nissan and Infiniti offer AWD systems for vehicles based on
either rear-wheel-drive or front-wheel-drive platforms. For
front-wheel-drive vehicles with a transverse-mounted
engine, such as Murano, the transfer case requires a
coupling to redirect power to the rear wheels when needed.
Certain Nissan and Infiniti vehicles offer a sophisticated
“intelligent” all-wheel-drive system that uses microprocessors
to deliver optimum power to each axle.
• Under normal road conditions, the system operates in
2-wheel drive for improved fuel efficiency.
• As necessary, the all-wheel-drive system automatically
engages all-wheel drive for stable, no-slip start-ups and
optimizes power distribution for improved driving stability.
Advantages
The design benefits of the Automatic 4WD and AWD
systems are threefold:
• When operating in 4-wheel drive, they provide optimum
control on snow, slippery surfaces, and rough terrain.
• Because both systems operate in 2-wheel drive on dry
road surfaces, they provide good fuel economy with
less steering effort and wear.
• Switching from 2-wheel drive to 4-wheel drive is
automatic. It happens when it’s needed.
ATTESA E-TS (Advanced Total Traction
Engineering System for All Electronic
Torque Split)
ATTESA E-TS is an advanced AWD system that
automatically distributes engine power among the four
wheels depending on driving conditions. It is derived from
the same system used on the legendary Skyline GT-R
in Japan.
The system automatically directs power to the front axle for
stable, no-slip start-ups. The amount of power directed to
the front varies according to the vehicle. If no wheel slips,
power is quickly adjusted to up to 100% rear-wheel
delivery. The system varies power distribution for improved
driving stability under various road conditions.
Advantages
The design benefits of the ATTESA E-TS system are
fourfold:
• When starting from a full stop in slippery conditions, it
provides sure traction and stable, smooth acceleration.
• It provides sporty cornering and handling even in
snowy or slippery conditions.
• Yet, it provides good fuel economy and smooth
handling on normal, dry road surfaces.
• Finally, snow mode can be engaged to increase control
when accelerating in snow or other slippery conditions.
Snow mode slows the rate of throttle opening at all
speeds for optimum control of wheel slippage.
when driving in snow, on slippery roads, or off-road. That’s
why all Nissan and Infiniti vehicles are available with a
variety of advanced traction and stability control systems
that enhance drivetrain characteristics.
Limited-slip differential
A limited-slip differential increases traction and vehicle
stability by automatically distributing engine power to the
drive-wheel that has the most traction. On a vehicle without
a limited-slip differential, once a drive-wheel begins to spin,
power continues to be directed to the spinning wheel. A
limited-slip differential helps provide good traction for
driving on slippery roads as well as dry, smooth road
surfaces, which increases driver confidence and enjoyment.
Dana axles
The limited-slip rear differential available on the previousgeneration Pathfinder, Xterra, and Frontier is pressuresensitive. The thrust from the spinning wheel forces the
gears to turn the opposite wheel.
In addition, Nissan Titan features a standard Dana rear axle
with a 2.94 gear ratio for fuel-efficient highway driving.
With the towing and off-road packages, however, Titan
gets a special axle based on the Dana-44. It has a 3.36
axle ratio that provides enhanced low-speed response in
off-road and towing conditions.
Nissan and Infiniti full-size SUVs have an independent rear
suspension instead of a solid rear axle. However, they use
Dana rear driveshafts (“half shafts”) that offer a 3.36 axle
ratio for enhanced towing capability (see illustration).
(Note: Combined with the lower 1st gear ratio of the
5-speed automatic transmission, the 3.36 axle ratio is
equivalent to a 4.10 axle ratio on a vehicle with a 4-speed
automatic transmission.)
Front
axle
Standard rear
axle/ratio
Optional rear
axle/ratio
Titan
Dana
Dana axle/2.94
Dana axle/3.36
Armada
Dana
Dana half
shafts/2.94
Dana half
shafts/3.36
QX56
Dana
Dana half
shafts/3.36
—
TRACTION AND STABILITY
CONTROL
Transferring power smoothly and effectively to the drivewheels is an important consideration in any vehicle, especially
Viscous Limited-Slip Differential (VLSD)
If a vehicle has a Viscous Limited-Slip Differential (VLSD),
the sealed differential housing is filled with temperaturesensitive silicone-based fluid that expands rapidly when
heated. Inside the differential housing are a series of
interlacing plates. One set is connected to the left drivewheel and one set to the right drive-wheel. Under normal
driving conditions, when both drive-wheels are traveling at
the same speed, the plates are all rotating together at the
same speed. But if one wheel begins to spin, one set of
plates within the differential will begin to turn much faster
than the other set.
Because the plates are very close together, this motion of
the plates relative to each other causes the fluid to heat
and expand. The expanding fluid forces the plates together,
so that the slower-turning set of plates absorbs torque
from the faster set.
The result is that the wheel with better traction receives
power from the wheel that is spinning faster so that overall
traction is improved.
Helical Limited-Slip Differential (HLSD)
The Helical Limited-Slip Differential (HLSD) uses a set of
gears inside the differential to control power flow. “Helical”
is the name for the angle at which the gears are cut. This
gear-driven system is more sensitive to torque and responds
more quickly than a viscous, or liquid-based, system.
A helical gear system generally has the following
advantages over other limited-slip differential designs:
• Its function is not affected by ambient temperature or
vehicle operating temperature.
• It can provide different traction management
characteristics for acceleration versus deceleration.
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DRIVETRAINS
A brand-name Dana front axle is standard on all Nissan and
Infiniti 4x4 full-size vehicles (also applied on selected
Xterra and Frontier models). This axle is built to handle the
heavy-duty requirements of both towing and off-road driving.
position. HDC is temporarily deactivated when the driver
presses the brake or accelerator pedals. For best results,
HDC should be used in 1st or 2nd gear.
g
To ri
f
To le
t axl
ht ax
le
e
Direction
of rotation
• It does not depend on internal friction material or
components that can wear.
• It will not interfere with ABS, which can happen with other
limited-slip differential designs under extreme conditions.
Locking rear differential
A locking differential literally locks the right and left axles
together so both rear wheels turn at the same speed,
sending an equal amount of power to each drive-wheel
at all times. In severe off-road, low-traction situations,
it’s important to keep both wheels turning, not slipping, so
the vehicle can crawl out of mud, sand, gravel, or other
difficult conditions.
The sophisticated electronically controlled switch-ondemand system gives drivers more control than a mechanical
locking differential. The system operates only in 4LO at
speeds up to 12 mph. It disengages if 4H is selected.
Limited Slip (ABLS)
Active brake limited slip (ABLS) is not a differential, but like a
limited-slip differential it redirects power to the drive-wheel or
drive-wheels that have better traction. It applies braking force
to any wheels that are slipping to help slow them down so
they can maintain grip and/or transfer power to the wheel(s)
that have better traction. 2-Wheel Limited Slip (ABLS)
applies braking force to either drive-wheel of 2-wheel-drive
vehicles. 4-Wheel Limited Slip (ABLS) applies braking force
to any of the drive-wheels of 4-wheel-drive vehicles.
Hill Descent Control (HDC)
Hill Descent Control (HDC) helps drivers maintain a
controlled speed on downhill slopes without having to use
the brakes. The driver is free to concentrate on steering. It is
available on selected Frontier, Xterra, and Pathfinder models
equipped with automatic transmission and 4-wheel drive.
HDC works below 15 mph on steeper slopes where
engine braking alone is not enough to control vehicle
speed. It operates in forward and reverse gears, but only in
4-wheel drive (4H or 4LO) with the HDC switch in the ON
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Hill Start Assist (HSA)
When the vehicle is stopped on an incline, Hill Start Assist
(HSA) automatically keeps the brakes applied to help
prevent the vehicle from rolling downhill during the interval
between the time the driver releases the brake pedal and
applies the throttle. It works when the vehicle is in 2-wheel
or 4-wheel drive and in forward or reverse gears. No driver
input is needed to turn the system on, but the driver must
apply the brake pedal to activate HSA and has two seconds
to apply the throttle before HSA deactivates. It is available
on selected Frontier, Xterra, and Pathfinder models
equipped with automatic transmission and 4-wheel drive.
Clutch start cancel switch
A clutch start cancel switch allows the driver to start the
vehicle without depressing the clutch. It is useful if the
vehicle’s engine stalls on a steep hill and the driver does
not want the vehicle to roll downhill when restarting.
The ignition must be in the ON position to activate the
clutch start cancel switch. Clutch start deactivates after
the vehicle has been started, so the driver must either
depress the clutch pedal or reactivate the switch to start
the vehicle again. This feature is available on selected
Frontier and Xterra models equipped with manual
transmission and 4-wheel drive.
Traction Control System (TCS)
Traction control limits drive-wheel slippage (wheel spin)
under most conditions. It does so by sensing impending
traction loss and correcting it to maximize vehicle stability
and driver control.
Loss of traction (wheel spin) occurs when acceleration
forces exceed the friction capability of one or more tires.
TCS uses the four wheel sensors of the Anti-lock Braking
System (ABS) to detect a loss of traction. The TCS
computer averages the speed of the two driven wheels and
compares that speed to the average speed of the nondriven wheels. If the average speed of the driven wheels
exceeds the average speed of the non-driven wheels by a
predetermined amount, “slip” is indicated and TCS goes
into operation.
The system controls the engine throttle, momentarily shuts
off one or several fuel injectors, and/or upshifts the
transmission to reduce power to the rear wheels.
Note: The Traction Control System on the firstgeneration Q45 operates differently than the system on
the current Q45. The system on first-generation Q45
operates by first closing a secondary engine throttle to
reduce power. Second, but almost simultaneously if
wheel spin persists, the rear brakes are applied to slow
the spinning wheel or wheels. An important feature of
this system is that it can independently control the left
rear or right rear wheel.
• Four wheel-speed sensors monitor the speed of each
wheel individually, and compare wheel speed to actual
vehicle speed.
There are many scenarios — especially in winter driving —
in which TCS excels:
• The steering angle sensor monitors the angle of the
steering wheel to help determine if the vehicle is going
in the intended direction.
• To provide traction on slippery surfaces, TCS
automatically controls drive-wheel traction and power
delivery. Applicable conditions include ice, snow, sand,
dirt, water, and gravel.
• For cornering performance, TCS minimizes wheel slip
due to over-acceleration or a change in road surfaces.
• To provide stability during fluctuating side winds, TCS
eliminates the need for the driver to modulate the
throttle to maintain directional stability during high
winds or sudden lane changes.
Vehicle Dynamic Control (VDC)
• The yaw rate/lateral g-sensor is located in the center
of the vehicle and monitors the vehicle’s position in
relation to the road. “Yaw” refers to how much the
vehicle rotates around its center axis. “Lateral g’s” refer
to forces exerted on the vehicle from the side. The
sensors help determine if the vehicle is moving in a
direction it’s not supposed to — for example, if it’s
sliding through a curve.
Together, all seven sensors provide the VDC control unit
with information about the vehicle’s behavior at any instant.
Based on this information, the VDC control unit sends a
signal to actuate the ABS, traction control, and throttle as
necessary to help maintain vehicle stability.
Compensating for oversteer and understeer
VDC takes stability control a step further. It helps enhance
performance in emergency avoidance maneuvers, helps
improve vehicle stability, and helps provide improved
control on slippery surfaces. VDC works in conjunction
with the ABS, TCS, and 2-Wheel or 4-Wheel Limited Slip
(ABLS) to improve traction and directional stability. Based
on input from various sensors, VDC controls the amount of
engine power and/or applies brake pressure to individual
wheels as needed.
Without VDC
Target Line
How VDC works
Seven sensors determine the vehicle’s operating
characteristics at any given instant.
VDC applies brake pressure to the outside
wheels to reduce oversteer.
VDC/TCS/ABS
actuator
Front wheel
speed sensors
With VDC
Rear wheel
speed sensors
VDC controller
VDC off switch
Target Line
If a vehicle “oversteers”
when driving through a
slippery curve, the
back of the vehicle will
tend to slide outward.
With VDC on, the
system senses the
beginning of the slide
and reacts by braking
the outside wheels and
reducing engine power
to generate force in the
opposite direction of
the spin. This helps
hold the vehicle to the
intended line of travel.
Relay
box
Precharge pump
VDC buzzer
Steering
angle sensor
Yaw rate/lateral
G-sensor
Encyclopedia I 9
DRIVETRAINS
The system works automatically, but can be switched off by
the driver. The system automatically re-engages every time
the engine is started.
• The brake pressure sensor monitors the amount of
brake pressure being applied to the wheels.
If a vehicle “understeers”
on a similar curve, the
front wheels lose
traction and push out
beyond the intended
line of travel. In this
situation, VDC applies
brake force to the inside
wheels and reduces
engine power. The front
wheels regain their grip,
and the driver can
maintain the intended
line of travel.
In both cases, full power
becomes available again
as soon as VDC has
helped stabilize the
vehicle. (This immediate
return of power is a
distinct advantage over
the systems in some
competitors.)
Without VDC
Target Line
FOR ADDITIONAL
INFORMATION
Every vehicle product guide lists the applicable
drivetrain features described in this chapter. Be sure
to study each product guide to determine which
features are available on each vehicle, and to review
the advantage and benefit for each feature.
Resource materials that provide additional information
about Nissan and Infiniti drivetrains include the
following:
With VDC
NPLS/Sales Encyclopedia Video Library
on DVD
Target Line
• Nissan Engine, Drivetrain, and Electrical Systems
• Advanced Technologies (Traction Control System)
• All-Mode 4WD
• Selling the Benefits of Vehicle Dynamic Control
VDC applies brake pressure to the
inside wheels to reduce understeer.
ILS/Sales Encyclopedia Video Library
on DVD
• Advanced Technologies (Traction Control System)
Benefits of VDC
Vehicle Dynamic Control is an important control safety
feature. It helps compensate for oversteer and understeer
by controlling brake pressure in one or more wheels and by
controlling engine power output. It even counteracts driver
input, if necessary. It enhances performance in emergency
avoidance maneuvers and helps provide improved control
even on slippery road surfaces. And it works automatically
and seamlessly — in fractions of a second.
Note: The VDC system is designed to help improve driving
stability. It does not prevent accidents due to abrupt
steering at high speeds or by careless or dangerous
driving techniques.
10 I Encyclopedia
• All-Mode 4WD (Revised)
• Selling the Benefits of Vehicle Dynamic Control
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