and Industry Terminology
knowledgeable about your vehicle begins with having a good
understanding of the different components and the names and terms used
to describe them.
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- Honda's Automatic Torque Transfer System
The system distributes the engines
torque output proportionately between the driven axles.
hydraulic fluid used in Honda's Automatic Torque Transfer System.
Auto Shift Lock/Starter Safety Switch
A safety device that locks the shifter in the Park position until the
brake pedal is depressed. It also prevents the vehicle from
starting unless the vehicle is in Park or the neutral position.
Automated Manual Transmission
referred to as "DSG," "direct shift gearbox," "SMG" and "sequential
manual gearbox." A conventional clutch-type manual
transmission that employs electronic, pneumatic and/or hydraulic
actuators in place of a conventional clutch pedal, and a purely
mechanical shift lever. The driver may select either fully automatic
shift mode or driver-controlled shift mode.
front wheel drive (FWD) vehicles. A transaxle is an automatic
transmission that is combined with the drive axle assembly.
See "Automatic Transmission"
Automatic Transaxle Pressure Filter
filter on an automatic transmission.
An automatic transmission (also called automatic gearbox) is a complex
motor vehicle transmission that automatically changes gears without the
need for driver input. The transmission delivers the engines power and
torque to the drive wheels using different gear ratios. Some
of the major components in an automatic transmission include a torque
converter, an oil pump, a planetary gear set assembly and friction
clutches and bands. Today, more than 90% of all new vehicles sold in
North America are equipped with automatic transmissions/transaxles.
circular metal straps lined with a friction material that are
hydraulically actuated to tighten around and stop the rotation of a
drum as part of the shifting process.
Transmission Clutches and Clutch Packs
Clutches (or friction clutches) are
round discs that engage and disengage with gear changes. When
engaged, the friction material on the clutch disc locks it to the
appropriate gear enabling the engine's power to be transmitted to the
drive wheels. When clutches wear out, slipping
Automatic Transmission Auxiliary Oil
aftermarket "secondary" transmission oil/fluid cooler designed to
increase the cooling capabilities of the factory installed transmission
fluid cooling system.
Automatic Transmission Oil Cooling
transmission oil/fluid cooling system that uses the engine's radiator
to cool the transmission oil. The hot transmission oil is
routed through a section of the radiator where the fluid is cooled
before being routed back to the transmission.
Automatic Transmission Cooler Hoses
aluminum tubes or flexible hoses that carry transmission fluid to and
from a heat exchanger or oil cooler.
Automatic Transmission Filter
in most automatic transmissions that is fitted over the fluid intake,
(usually located in the oil pan), that prevents debris and other
contaminants from circulating through the transmission's inner workings
and potentially causing excessive wear, blockages and damage.
Some transmissions use a reusable metal or nylon mesh-type screen in
place of a disposable/replaceable filter.
Automatic Transmission Fluid (ATF)
Automatic transmission fluid (ATF) is
the fluid used in vehicles equipped with automatic transmissions. The
fluid is typically red in color so it can be easily distinguished from
engine oil and other vehicle fluids. Transmission fluid is
specially formulated to lubricate and cool the transmission while
providing the hydraulic pressure needed to shift gears and engage and
disengage bands and clutches. ATF is used in many manual
transmissions, 4-wheel drive (4WD) transfer cases and power steering
AWD or All-Wheel Drive
A drivetrain that employs a front,
rear and center differential to provide the engine's power to all four
wheels of a vehicle.
Transmission Rebuild Kit
A preassembled set of parts
that are used in rebuilding an automatic transmission.
Depending on the vehicle, year, make and model and the kit chosen,
automatic transmission rebuilder kits typically include a paper and
rubber kit, seal kit, steel plates, friction clutches, filter,
modulator, bushing kit, bonded pistons, flex band and popular
washers. Rebuilder kits do not include hard parts.
Transmission Repair Shop
An automotive repair shop that
specializes in servicing and repairing automatic
transmissions. Transmission repair shops employ technicians
with specialized training in automatic transmission service and
repair. General automotive repair shops typically do not
provide specialized transmission services.
A trained (and oftentimes) certified
automatic transmission professional. This is the person that
will diagnose your transmission problems and make the necessary
repair(s). These technicians have extensive training in
diagnosing, servicing and repairing/rebuilding all makes and models of
automatic transmission and transaxles.
Axle Drive Fluid
used for lubricating gears inside the axle.
ratio of a gear train assembly. By using input and output gears with
different teeth counts, various gear and axles ratios are achieved.
Also called OBD-II Scanner.
A device used to read a vehicle's onboard computer and extract the
code(s) that have triggered a check engine light situation.
Velocity Joint (or CV Joint)
either end of the drive axles, cv joints transmit engine power while
enabling full steering and suspension movement. Black accordion type
rubber covers (cv boots) cover and protect these joints from debris and
damage. CV boots are filled with lubricant to keep the cv
Continuously Variable Transmission or
transmission with a continuously variable drive ratio (as opposed to
conventionally stepped gear ratios) that maintains a steady
acceleration curve with no pauses for gear changes.
Declutching/Freewheeling The act of disengaging a vehicles transmission
from its driveshaft, either manually or automatically, when its drive
shafts RPM exceeds the transmissions RPM.
used for lubricating gears inside the differential.
A transmission cable connected to the
throttle that shifts the transmission into a lower gear when the
accelerator is depressed suddenly beyond a certain point.
Most people know this as passing gear.
flexible, conical, accordion-like covers that contain lubricant and
protect the constant-velocity joints on a drive axle shaft.
A long round
"tube-like" metal part that connects the transmission to the
differential on a rear-wheel or four-wheel drive vehicle. On
either end of a drive shaft are u-joints or universal joints.
The type of
drive system or drivetrain of a vehicle; two-wheel drive, four-wheel
drive or all-wheel drive.
typically made of metal and hard rubber material to attach a vehicles
drivetrain components to the vehicle chassis. These "mounts"
absorb much of the energy produced between the mounted parts and the
The parts of a vehicle that generates
power and transfers the power to the vehicle's wheels.
manufacturer's warranty or aftermarket warranty that covers the
drivetrain, i.e., engine, transmission, driveshaft, differential and
warranty sold by the vehicle manufacturer/dealership or by a third
party service provider that extends the vehicles basic warranty beyond
the manufacturer's standard warranty period.
FWD or Front Wheel Drive
Front-engine front-wheel drive. A vehicle that is propelled
solely by its front wheels and whose engine is located forward of its
front axle. Front wheel drive automatic transmissions are
called transaxles because the transmission and axles are one component.
Four Wheel Drive or 4WD
A vehicle that uses two differentials and a transfer case to transfer
the engine's power to all four drive wheels. Normally these
vehicles can be driven in either two-wheel drive or four-wheel drive
coupling used in vehicles with automatic all-wheel drive systems to
engage and disengage a secondary axle when needed.
Automatic transmission parts fall into
one of two categories; soft parts and hard parts. The hard
parts are the parts that are not part of a standard rebuild kit and
that typically do not need to be replaced as part of a standard
transmission overhaul. Hard parts include the pump, clutch
drum, output shaft, planetary gears, etc.
drivetrain layout in a hybrid vehicle: parallel, series or combined.
warranty that is in effect for a specified number of years and/or miles
of forward gears of a transmission. Most automatic
transmissions have 4-speeds, but 5, 6, 7 and even 8-speed automatic
transmission are available in some high-end luxury and sports cars.
for Original Equipment Manufacturer. OEM replacement parts
are considered to be of higher quality that most aftermarket auto parts.
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with capable of traveling off-road. These vehicles are
typically 4 wheel drive with all-terrain tires and high ground
Also referred to as the "drivetrain
warranty", a powertrain warranty covers the parts of the vehicle that
make it move, including the engine, transmission, drive axles and
for "Revolutions Per Minute", which is the number of revolutions the
pistons of an engine turn in one minute.
RR stands for "Rear-Engine
Rear-Wheel Drive", which
means what it says; the engine is in the rear of the vehicle and the
engines power is transferred to the rear wheels only. Some
vehicles with a RR drivetrain configuration include some Porsche models
and the Volkswagen Beetle.
RWD or Rear Wheel Drive
A vehicle that uses a transmission and driveshaft to deliver the
engine's torque and power to a rear differential and then to the rear
wheels. Examples of rear wheel drive vehicles include the
Chevrolet Camaro and Corvette, the Ford Mustang, Dodge Challenger,
Lincoln Town Car and of course pick-up trucks.
A warranty that covers service
procedures recommended by the manufacturer at predetermined intervals
to preserve and/or prolong the life of a vehicle.
Sequential Manual Gearbox
referred to as "SMG," "direct shift gearbox," "DSG" and "automated
manual transmission." See "Automated Manual Transmission."
Service Reminder Light
A light that indicates that general
vehicle maintenance is needed or that a specific service is required.
of the shift control mechanism, which includes levers, paddles or
collection of mechanical connections between a vehicles operating
control(s) and its transmission.
The means by
which a driver changes gears, including buttons, paddles or a lever.
Shiftable Automatic Transmission
torque converter transmission equipped with a feature that permits the
driver to actively select either fully automatic or driver-controlled
shift modes by using a dual-gate shifter and/or remote shifter controls.
typically attached to the bottom of a vehicles front bumper that is
designed to guard the undercarriage in the case of insufficient ground
Slipping or Transmission Slip
Slipping is a term used to describe an
automatic transmission that is unable to transfer the engine's torque
(or output) to the drive wheels either partially or fully.
Low transmission fluid, a clogged transmission filter and burnt or worn
out clutches can cause slipping.
manual gearbox is an automated manual transmission. It is an
automatic gearbox that can be shifted manually. Typically
only found in high-end sports cars.
as "electronic stability control," or "ESC." A safety feature that
improves the safety of a vehicles handling by detecting skids and
compensating by adjusting braking pressure to help maintain the
intended direction of the vehicle. Some stability control systems also
reduce engine power until control is regained.
Starter Safety Switch
Also called Neutral Safety
Switch. A vehicle safety feature that prevents a vehicle from
being started unless the shifter lever is in Park or Neutral in
vehicles equipped with automatic transmissions or the clutch pedal
depressed in vehicles equipped with standard/manual
instrument that tells the driver how many revolutions per minute (RPMs)
the pistons of the engine are turning.
Sometimes referred to as "TSB" is a
bulletin put out by vehicle manufacturers to advise vehicle owners of a
problem with a particular vehicle year and model.
Throttle & Kick-Down Lever
pivot points for the throttle or kick-down linkages of the transmission.
measurement of an engine's power that indicates how forcefully it can
rotate the crankshaft at a given engine speed.
The torque converter is to an
automatic transmission as a clutch is to a manual/standard
transmission. The torque converter controls the automatic
transmission fluid/pressure that reaches the transmission, which
effectively controls the engagement of clutches and gears.
with features and equipment that make it well-suited for pulling a
trailer. Towing capable vehicles with automatic transmissions
are usually equipped with an external transmission oil cooler.
The maximum amount of weight a vehicle
is capable of towing (according to its manufacturer).
Exceeding the vehicle's towing capacity can cause the vehicle's gearbox
to overheat. As you will read throughout this Web site,
excessive heat is an automatic transmission's worst enemy.
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Control System or TCS
feature that regulates wheel spin and prevents loss of control under
acceleration by ensuring maximum traction and contact between the tires
and the road surface. This is accomplished by adjusting brake
pressure, reducing the throttle and/or reducing the fuel supply to one
or more cylinders in order to reduce the power to the drive wheels.
device attached to a structurally sound section of a vehicles frame
that is used to support a trailer while coupling it to the vehicle.
used in the transfer case.
transmission settings that change drive ratios and/or shift points for
fuel economy or performance.
Where the filter and valve body
reside. The pan typically holds between 3 to 4 quarts of the
transmission fluid used in the transmission.
A final gear ratio for an automatic
transmission that has an output speed greater than its input speed,
which increases highway fuel economy. Most automatic
gearboxes today have an overdrive gear.
type of transmission, i.e., automatic, manual, semi-automatic,
shiftable automatic or automated manual, CVT.
Universal Joints or U-joints
joints used on drive shafts that are composed of two U-shaped yokes
that share a common cross-shaped member.
The area of
a vehicle that is typically not visible from above and that is exposed
to the road.
Flexible tubing used in vehicle
engines and transmissions to carry air, fluids, vapors or pressurized
The part of an automatic transmission
or automatic gearbox which serves as the hydraulic control
center. The pressurized fluid received at the valve body is
directed to the clutches and transmission bands in a way that engages
the appropriate gear configuration for the travel condition. The valve
body receives pressurized fluid from the main pump of the transmission
operated by the torque converter and then directs the pressurized fluid
with the use of valves and servos to the appropriate clutches and bands
of transmission to engage the most appropriate gear configuration for
the driving conditions.
Identification Number or VIN
Also referred to as "VIN." This is the number that identifies
the vehicle manufacturer, year, model, place of manufacture,
etc. Using this number when ordering parts helps insure you
are ordering the correct parts. Get the details for any
vehicle - free VIN decoder.
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