Two Wheel Drive vehicle

A two-wheel drive vehicle with four wheels. The first figure is the number of wheels. The second is the number of powered wheels.

Four Wheel Drive: A system that powers all four wheels at all times. Each tire creates about 25% of the available torque when the ground is level with a consistant surface. Driver has a choice of a "4-high" (that's your every day setting) and "4-low". The first figure is the number of wheels. The second is the number of powered wheels.

the roof support on either side of A car's windshield.

Mass ratio of air to fuel present during combustion.

Automatic Four-Wheel Drive: This type of drive system automatically engages 4WD as needed. When internal monitors sense differences in individual wheel speeds, indicating that a tire is slipping, then 4WD is automatically engaged

Active Brake Limited Slip, or ABLS, applies brakes selectively to the slipping wheel(s). This braking action forces the open differential(s) into sending power everywhere except the slipping wheel(s). In essence the ABLS system gives you two �limited slip differentials� � front and rear � to ensure maximum traction, without the costs associated with a true limited slip differential. On a 4X2 Titan, only the rear wheels have ABLS.

Anti-Lock Brake system: A braking system that senses when any of the wheels have locked up, or are about to, and automatically reduces the braking forces to keep the wheels rolling

The drag produced by a moving object as it displaces the air in its path. Aerodynamic drag is a force usually measured in pounds; it increases in proportion to the object's frontal area, its drag coefficient, and the square of its speed.

Air to Fuel Ratio: The proportion of air and fuel present during combustion.

Air Bags: A system of very fast opening bags that are filled with Nitrogen upon frontal impact or with the roof-mounted curtain supplemental air bags also protect from side impact. In the front one air bag is mounted in the center hub of the steering wheel. The passenger side air bag deploys from the dash in front of the passenger seat. The passenger air bag is also controlled by a weight sensor in the passenger seat. Unless a person of sufficient weight is sitting in the passenger seat, it will not deploy.

A front spoiler mounted beneath the bumper and shaped to reduce the airflow under the car. Air dams can increase the airflow to radiators, reduce aerodynamic drag, and/or reduce lift.

Amperes: Electrical flow (current) in an electric or electronic circuit.

A tuned-in front suspension characteristic that converts braking-induced forces in the suspension links into a vertical force that tends to lift the body, thereby reducing dive under braking.

A suspension element (used at the front, the rear, or both ends of a car) that reduces body roll by resisting any unequal vertical motion between the pair of wheels to which it is connected. An anti-roll bar does not affect suspension stiffness when both wheels are deflected equally in the same direction. Often incorrectly called a sway bar.

Similar to anti-dive, this suspension characteristic uses acceleration-induced forces in the rear suspension to reduce squat.

The point(s) or region on the line through a corner that touches the corner's inner radius.

This sensor detects the accelerator position and sends a signal to the ECM.

Steering wheel cruise control.

Generally the ratio between two dimensions of an object. In tire terminology it applies to the unloaded sidewall height of the tire divided by its overall width. A lower aspect ratio implies a shorter, wider tire. When used to describe a wing it is the span of the airfoil (the long dimension perpendicular to the airflow) divided by its chord (the dimension parallel to the airflow).

All Wheel Drive: A full-time single-speed system designed to supply drive power to all four wheels at all times.

A form of wheel hop that occurs on cars with live axles, caused by the axle repeatedly rotating slightly with the wheels and then springing back.

The roof support between a car's front door window and rear side window, if there is one.

A shaft designed so that, as it rotates, it vibrates in a way that reduces or cancels some of the vibration produced by an engine. Not essential to an engine's operation, balance shafts are nonetheless becoming increasingly common as a means of engine refinement. Balance-shafted four-cylinder engines use two shafts turning in opposite directions on either side of the engine's crankshaft. A single balance shaft is used when fitted to three-cylinder and V-6 engines.

A flexible joint consisting of a ball in a socket, used primarily in front suspensions because it can accommodate a wide range of angular motion.

A rigid axle supporting the non-driven wheels. Also called a dead axle.

Bearings: Are anti-friction devices and come in many forms. Plain, ball, roller, tapered roller, thrust and sintered metal. Most are familiar with ball bearings, where a number of very hard balls rotate between two races. Roller bearings utilize a cylindrical shape rather than a spherical ball. Roller bearings are sometimes tapered and the rollers more closely resemble truncated cones. Thrust bearings are designed so that the thrust forces of a rotating shaft are contained in the bearing and maintains the position of the shaft. Plain bearings are use in supporting crankshafts and cams. Typically, the plain bearing contains a soft metal bonded to a harder metal backing plate. Plain bearings don't support the rotating shaft on the soft metal, but on a film of oil. The soft metal provides a place for the shaft to rest when stopped and also a surface for wear particles to embed into. Cams often rotate in bored aluminum supports with only an oil film as the bearing surface. Sintered metal bearings, sometimes called "oilite" are particles of bearing bronze mixed with a thick oil and then compressed into a solid. Generally used on slow moving or pivoting shafts and the oil means they are self-lubricating.

The line running around a car's body formed by the bottom edges of its glass panels

A gearset employing gears shaped like slices of a cone, which allows the axes of the gears to be nonparallel. Bevel gears are used to transmit motion through an angle.

Big Tow is the Nissan name for a package of additional or upgraded equipment added to the Titan to facilitate towing. It increases towing capacity to 9500, adds a larger battery, lower differential gear ratio, transmission temperature gauge, Class IV receiver hitch, extendable mirrors with wide view section, 7 pin wiring harness & trailer brake controller pre-wiring under the dash.

The increase above atmospheric pressure produced inside the intake manifold by any supercharger. It is commonly measured in psi, inches of mercury, or bar.

The front/rear distribution of a car's braking power. For the shortest stopping distance, brake bias should match the car's traction at each end during hard braking brake modulation: the process of varying pedal pressure to hold a car's brakes on the verge of lockup. Ideally, the brakes will unlock with only a slight reduction in the pressure needed to lock them. Typically, however, a considerable pressure reduction is required.

Brake Judder: The overwhelming cause of brake judder is a condition called Disc Thickness Variation. The Rotor develops a lack of parallelism between its inboard and outboard friction surfaces.

A procedure generally used in performance tests to improve the off-the-line acceleration of a car equipped with an automatic transmission. It is executed by firmly depressing the brake with the left foot, applying the throttle with the car in gear to increase engine rpm, then releasing the brakes. Brake torquing is particularly effective with turbo charged cars because it helps overcome turbo lag.

A term used to describe an engine's ability to fill its cylinders with air-fuel mixture and then discharge the burnt exhaust gases. In general, the more air-fuel mixture an engine burns the more power it produces.

Bumpsteer is a change in toe angle caused by the suspension moving up or down. This toe change or “steering” occurs any time the suspension moves, whether it is from body roll, brake-dive, or hitting a bump in the road. Bumpsteer is undesirable because the suspension is steering the car instead of the driver. For more on bumpsteer see http://www.modularpower.com/bumpsteer.html

A simple suspension bearing that accommodates limited rotary motion, typically made of two coaxial steel tubes bonded to a sleeve of rubber between them. The compliance of the bushing in different directions has a great effect on ride harshness and handling. Bushings are also a form of sintered bearing. See the bearings definition.

The roof support between a car's rearmost side window and its rear window. On a vehicle with four side pillars, the rearmost roof support may be called a D-pillar.

Cold Air Intake: A system to provide air which is colder than that found in the engine compartment. Air is drawn from outside the engine compartment, and in the case of the Titan from inside the left front fender.

The shape of each lobe on a camshaft. The profile determines the amount, or ""duration,"" of time the valve is open; it also largely determines the valve's maximum opening, or ""lift."" camber: the angle between the plane of a wheel's circumference and a vertical line, measured in degrees and minutes. The tops of a car's wheels tilt inward when the camber is negative, outward when it is positive.

the angle between the vertical axis of the wheel and the vertical axis of the vehicle when viewed from the front or rear

A shaft fitted with several cams, whose lobes push on valve lifters to convert rotary motion into linear motion. The opening and closing of the valves in all piston engines is regulated by one or more camshafts.

On vehicle multiplex communication line with high data communication speed and excellant error detection ability

Thread-like strands of pure carbon that are extremely strong in tension (that is, when pulled) and are reasonably flexible. Carbon fiber can be bound in a matrix of plastic resin by heat, vacuum, or pressure to form a composite that is strong, light: and very expensive.

The angle between a vertical line and the car's steering axis when viewed from the side, measured in degrees and minutes.

a stainless-steel canister fitted to a car's exhaust system that contains a thin layer of catalytic material spread over a large area of inert supports. The material used is some combination of platinum, rhodium, and palladium; it induces chemical reactions that convert an engine's exhaust emissions into less harmful products. So-called three-way catalysts are particularly efficient; their operation, however, demands very precise combustion control, which can be produced only by a feedback fuel-air-ratio control system.

Cat Back: A term that means from the Catalytic Converter to the tip of the tail pipe. Replaces all the exhaust system except the catalytic converters and exhaust headers.

truck with 4 full size doors.

A differential used in four-wheel-drive systems to distribute power to the front and rear differentials

A general term that refers to all of the mechanical parts of a car attached to a structural frame. In cars with unitized construction, the chassis comprises everything but the body of the car.

It's located on the A/T and detects fluctuation of the engine revolution.

The camshaft Position sensor senses the piston position.

A bar of resilient metal wound into a spiral that may be compressed or extended without permanent deformation. Coil springs have many automotive applications but are particularly important as suspension springs.

The space within the cylinder when the piston is at the top of its travel. It is formed by the top of the piston and a cavity in the cylinder head. Since most of the air-fuel mixture's combustion takes place in this space, its design and shape can greatly affect the power, fuel efficiency, and emissions of the engine.

transfer of information from one point ot another/

A slight resiliency, or "give," designed into suspension bushings to help absorb bumps. Good compliance allows the wheels to move rearward a bit as they hit bumps but doesn't allow them to move laterally during cornering.

Any material that consists of two or more components, typically one or more of high strength and one an adhesive binder. The most common composite is fiberglass, which consists of thin glass fibers bonded together in a plastic matrix. The structural properties of composites can be altered by controlling the orientation and configuration of the high-strength components.

The ratio between the combined volume of a cylinder and a combustion chamber when the piston is at the bottom of its stroke, and the volume when the piston is at the top of its stroke. The higher the compression ratio, the more mechanical energy an engine can squeeze from its air-fuel mixture. Higher compression ratios, however, also make detonation more likely.

The metal rod that connects a piston to a throw on a crankshaft.

A suspension element that has one joint at one end and two joints at the other end, typically the chassis side. Also known as a wishbone or an A-arm.

The maximum speed at which a car can negotiate a given curve.

A closed car with two side doors and less than 33 cubic feet of rear interior volume, according to measurements based on SAE standard J1100. A two-door car is therefore not necessarily a coupe.

A shaft with one or more cranks, or "throws," that are coupled by connecting rods to the engine's pistons. Together, the crankshaft and the con rods transform the pistons' reciprocating motion into rotary motion

A particular kind of universal joint designed so that there is no cyclic fluctuation between the speeds of its input and output shafts.

The round, straight-sided cavity in which the pistons move up and down. Typically made of cast iron and formed as a part of the block.

The aluminum or iron casting that houses the combustion chambers, the intake and exhaust ports, and much or all of the valvetrain. The head (or heads, if an engine has more than one bank of cylinders) is always directly above the cylinders.

The circular housing that the piston moves in when the cylinder is not an integral part of the block. Also known as a "sleeve."

A unit of measure for decibels, the measure of sound intensity or pressure named after Alexander Graham Bell. It is a logarithmic measurement; every 3dB increase represents a doubling of the sound pressure. The ""A"" in dBA indicates that the measurement was taken with an A-weighted scale; sound pressure varies across the audible spectrum, and the A-weighted scale approximates the human ear's sensitivity to various frequencies.

A suspension system in which the rear, driven wheels are bolted to a transverse, lightweight, rigid member. Power is delivered to the wheels by universal-jointed half-shafts attached to a body-mounted differential.

A footrest found to the left of the leftmost pedal. It provides a place for the driver to brace his left leg during hard cornering.

A condition in which, after the spark plug fires, some of the unburned air-fuel mixture in the combustion chamber explodes spontaneously, set off only by the heat and pressure of air-fuel mixture that has already been ignited. Detonation, or "knock," greatly increases the mechanical and thermal stresses on the engine.

A special gearbox designed so that the torque fed into it is split and delivered to two outputs that can turn at different speeds. Differentials within axles are designed to split torque evenly; however, when used between the front and rear axles in four-wheel-drive systems (a center differential), they can be designed to apportion torque unevenly.

Differential: This device allows the drive axles to rotate at different speeds. The axles rotate at different speeds when making a turn as the wheel on the outside of the turn has to travel further than the inside wheel. If there wasn't a differential, the outside wheel would drag all the way through the turn.

Properly called caliper disc brakes: a type of brake that consists of a disc that rotates at wheel speed, straddled by a caliper that can squeeze the surfaces of the disc near its periphery. Disc brakes provide a more linear response and operate more efficiently at high temperatures and wet conditions than drum brakes.

The dipping of a car's nose that occurs when the brakes are applied. Dive is caused by a load transfer from the rear to the front suspension; this transfer occurs because the car's center of gravity, through which all inertial forces pass, is higher than its contact patches, the points where the braking forces are exerted on the ground.

An instrument designed to measure electrical quantities. A typical multimeter can measure alternating- and direct-current potential differences (voltages), current, and resistance, with several full-scale ranges provided for each quantity. Sometimes referred to as a volt-ohm meter (VOM), it is a logical development of the electrical meter, providing a general-purpose instrument.

A double overhead camshaft (also called double overhead cam, dual overhead cam or twincam) valvetrain layout is characterized by two camshafts being located within the cylinder head, where there are separate camshafts for inlet and exhaust valves. In engines with more than one cylinder bank (V engines) this designation means two camshafts per bank, for a total of four.

A vertical force directed downward, produced by airflow around an object: such as a car body.

A dimensionless measure of the aerodynamic sleekness of an object. A sleek car has a drag coefficient, or "Cd," of about 0.30; a square, flat plate's is 1.98. Also signified by Cx.

The general qualitative evaluation of a powertrain's operating qualities, including idle smoothness, cold and hot starting, throttle response, power delivery, and tolerance for altitude changes.

Everything in the drivetrain, less the engine and the transmission.

All of a car's components that create power and transmit it to the wheels; i.e. the engine, the transmission, the differential(s), the hubs, and any interconnecting shafts.

A monotonous low tone; humming or buzzing sound

A type of brake that has an iron casting shaped like a shallow drum that rotates with the wheel. Curved brake shoes are forced into contact with the inner periphery of this drum to provide braking.

A machine used to measure Torque and Horsepower at the rear wheels of a immobile vehicle.

when the system is engaged for most E-Lockers, friction between an armature and an electromagnet apply force to a "ball ramp" mechanism. This forces the ball ramp's bearings out of their pockets and up the ramp. That action, in turn, pushes the system's locking pins into matching holes located on the back of the side gear. That locks the axle, and drives torque to both wheels.

an electronic control unit which controls various aspects of the engine.

The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.

A computerized brain that regulates an engine's operation by monitoring certain engine characteristics (rpm, coolant temperature, intake airflow, etc.) through a network of sensors and then controlling key variables (fuel metering, spark timing, EGR, etc.) according to pre-programmed schedules.

A method of reducing NOx (oxides of nitrogen) exhaust emissions by recirculating some of the engine's exhaust gas into the intake manifold. The exhaust gas serves as inert filler that absorbs heat during the combustion process and reduces the peak temperature reached during combustion

Laboratory fuel-economy tests administered by the Environmental Protection Agency using simulated weight and drag to re-create real driving conditions. The city fuel-economy test, also used to test emissions compliance, is based on a drive through typical Los Angeles urban traffic of about twenty years ago. Of course, such nostalgic conditions are purely nostalgic these days. The highway test uses a higher, steadier speed, averaging 49.4 mph.

One of many Emissions Control Systems

The network of passages that gathers the exhaust gases from the various exhaust ports and routes them toward the catalysts and mufflers of the exhaust system. A manifold with free-flowing passages of a carefully designed configuration, called a ""header,"" can improve breathing.

The passageway in the cylinder head leading from the exhaust valves to the exhaust manifold.

A feature of a computer-controlled fuel system. By using a sensor to measure the oxygen content of the engine's exhaust, the system keeps the fuel-air ratio very close to the proportion for chemically perfect combustion. Such tight control of the fuel-air ratio is mandatory for the proper operation of three-way catalysts.

A composite material that relies on small glass fibers for its strength.

The reduction ratio, found in the gearset of a drivetrain, that is furthest removed from the engine. Typically, the differential ratio.

The largest and most important stamped metal part in a car's body. Usually assembled from several smaller stampings, the floorpan forms the floor and fixes the dimensions for most of the car's external and structural panels. It is also the foundation for many of the car's mechanical parts.

Any device that transfers power through a fluid between its inputs and outputs. A fluid coupling basically consists of two fans in a sealed, oil-filled housing. The input fan churns the oil, and the churning oil in turn twirls the output fan. Such a coupling allows some speed difference between its input and output shafts.

A heavy disc attached to an engine's crankshaft to increase its rotary inertia, thereby smoothing its power flow.

A somewhat imprecise term that describes a cornering situation in which all four tires are operating at large slip angles.

A steering system that actively steers the rear wheels as well as the fronts to improve handling and maneuverability.

The number of complete cycles of a periodic process occurring per unit time. Or, The number of repetitions per unit time of a complete waveform, as of an electric current.

A thermistor used to detect the fuel temperature in the fuel tank and modifys a signal from the ECM and returns this modified signal back to ECM as the fuel temperature input. The resistance of the thermistor decreases as the temperature increases.

Any system that meters fuel to an engine by measuring its needs and then regulating the fuel flow, by electronic or mechanical means, through a pump and injectors. Throttle-body injection locates the injector(s) centrally in the throttle-body housing, while port injection allocates at least one injector for each cylinder near its intake port.

Full-Time Four Wheel Drive: Describes a four-wheel-drive system that can be operated continuously on all surfaces. A full-time four-wheel-drive system may include the option of part-time operation (allowing you to shift into 2WD on dry pavement for example), and may or may not have Hi and Lo speed ranges.

A valvetrain with a total of four valves in the combustion chamber, typically two intakes and two exhausts. Compared to the more common two-valve-per-cylinder designs, a four-valve layout offers improved breathing and allows the spark plug to be located closer to center of the combustion chamber.

The unit of measure for lateral acceleration, or "road-holding." One g is equivalent to 32.2 feet per second per second, the rate at which any object accelerates when dropped at sea level. If a car were cornering at 1.0 g: a figure that very few production cars are able to approach: the driver's body would be pushing equally hard against the side of the seat as against the bottom of it.

A group of two or more gears used to transmit power.

GPS: A system of 24 Satellites in a roughly 11,000 mile orbits. The GPS receiver needs to receive signals from at least three satellites to triangulate its position on Earth. A forth satellite is used as a check on accuracy. Very accurate Atomic Clocks are onboard each satellite. An error of just one-one thousandth of a second can result in an error of about 200 miles.

The portion of a car's body that rises above the beltline of the car.

The phenomenon that occurs when the airflow between a moving object and the ground creates downforce.

An articulating, rotating shaft used in independent-suspension systems to transmit power from a differential to a wheel.

A general term covering all the aspects of a car's behavior that are related to its directional control.

Head Unit: A term to include the main unit of the stereo system. Includes the radio and either a Cassette, CD or DVD player. The amplifier may or may not be included in the head unit. More expensive and higher performance units normally have separate amplifiers.

A performance-oriented technique of down-shifting while braking that requires the driver to use all three pedals of a manual-transmission car simultaneously. To perform a heel-and-toe downshift, the driver brakes with the toe of his right foot and: while continuing to brake: uses the heel or the side of the same foot to blip the throttle and raise engine rpm as he downshifts. The left foot operates the clutch pedal in the normal fashion. The sequence is as follows: brake with the right toe; depress the clutch with the left foot; shift to neutral; while continuing to brake, blip the throttle with the side or the heel of the right foot to raise rpm; shift to a lower gear; let the clutch out; release the brakes. The technique is difficult to master, but after practice it can be performed in less than a second. This process is best for smooth power flow and long transmission life.

An extremely rigid articulating joint, commonly known as a ""spherical rod-end,"" used in any precision linkage. Heim joints are often used in the suspension links of race cars because they locate wheels very precisely.

A type of gear in which the teeth are cut at a slanting angle to the gear's circumference. A helical design produces an even, constant tooth loading in a gearset, thereby reducing noise.

A term used to describe any engine that has hemispherical combustion chambers in its cylinder head. Although a four-valve design is more efficient, a hemi head provides room for a pair of large valves and offers good breathing characteristics.

High Intensity Discharge: This is a lighting system that differs from conventional incandesent lights like Halogen Headlights or the lights in your dome light which use a heated filament to create the light. HID lights use a high voltage arc to generate a plasma in the tube. After the plasma is generated, then it only takes a maintenance voltage/current flow to maintain the plasma. HID lights require an "ignighter" and a control module for each bulb.

Heated O2 sensor

A live-axle rear suspension in which leaf springs handle both the axle's springing and its location.

The common unit of measurement of an engine's power. One horsepower equals 550 foot-pounds per second, the power needed to lift 550 pounds one foot off the ground in one second: or one pound 550 feet up in the same time.

A valve lifter that, using simple valving and the engine's oil pressure, can adjust its length slightly: thereby maintaining zero clearance in the valvetrain. Hydraulic lifters reduce valvetrain noise and are maintenance-free.

This sensor is built into the Mass Air (MAF) Flow sensor and detects intake air temperature and transmits a signal to the ECM. The IAT uses a thermistor which is sensitive to the change of temperature. Electrical resistance of the thermistor decreases in response to temperature rise.

Any suspension in which the camber of a wheel is not directly affected by the vertical motion of the opposite wheel.

The mixture of fuel and air that flows into the engine.

The network of passages that direct air or air-fuel mixture from the throttle body to the intake ports in the cylinder head. The flow typically proceeds from the throttle body into a chamber called the plenum, which in turn feeds individual tubes, called runners, leading to each intake port. Engine breathing is enhanced if the intake manifold is configured to optimize the pressure pulses in the intake system.

The passageway in a cylinder head leading from the intake manifold to the intake valve(s).

A heat exchanger that cools the air (or, in some installations, the intake charge) that has been heated by compression in any type of supercharger. An intercooler resembles a radiator; it houses large passages for the intake flow, and uses either outside air or water directed over it to lower the temperature of the intake flow inside.

The target speed is the lowest speed the engine can operate steadily.

The motion of a wheel that compresses its suspension.

an elastic cushion used to stiffen the suspension gradually as it approaches the end of its jounce travel.

To shake rapidly or spasmodically; vibrate conspicuously. A rapid or spasmodic shaking

Truck with 2 full size front doors and 2 smaller rear doors that can only be opened after the front doors are. Smaller back seat than a Crew Cab but usually have more beds.

A downshift in an automatic transmission caused by depressing the throttle.

A sensor mounted on the engine that is designed to detect the high-frequency vibrations caused by detonation. By employing a knock sensor, a computerized engine-control system allows an engine to operate very near its detonation limit: thereby improving power and efficiency.

The knock sensor is attached to the cylinder block. It senses engine vibration from the cylinder block is sensed as vibrational pressure and is converted into a voltage signal and sent to the ECM.

A suspension link that is aligned to resist sideways motions in a wheel.

The unit of measurement for torque. One pound-foot is equal to the twisting force produced when a one-pound force is applied to the end of a one-foot-long lever.

A suspension link that is aligned to resist longitudinal motions in a wheel; it is mounted to the chassis behind the wheel.

A long, flat, thin, flexible piece of spring steel or various composite materials that deflects by bending when forces act upon it. Leaf springs are used primarily in suspensions.

LED: A semi-conductor diode which produces light through the application of electricty. Very long-lived, cool in operation and very fast in operation.

A vertical force directed upward, produced by the airflow around a moving object: such as a car body. Also referring to Body or Suspension lifts used to gain ground or tire clearance.

A handling characteristic that causes the rear tires to lose some of their cornering grip when the throttle is released during hard cornering.

A differential fitted with a mechanism that limits the speed and torque differences between its two outputs. Limited slip ensures that some torque is always distributed to both wheels, even when one is on very slippery pavement. The Detroit True-Trac is one example: http://www.detroitlocker.com/DT.htm

The path through a corner that best accommodates a late braking point, a high cornering speed, and the fastest-possible exit speed out of a corner.

A suspension member that has a single joint at each end.

A rigid axle incorporating a differential and axle shafts to power the two wheels it is supporting.

The juncture at which a tire starts to skid during braking. A tire's maximum braking force is developed when it is on the verge of lockup, so a car's shortest stopping distances are produced when its front and rear tires approach lockup simultaneously. This is very hard to achieve under varying conditions of load and traction, so one end typically locks up before the other. Front-wheel lockup is inherently more stable than rear-wheel lockup.

A differential whose two outputs can be locked together, eliminating any differential action but maximizing traction under slippery conditions.

A torque converter fitted with a lock-up clutch that can be engaged to eliminate the slip between the torque converter's input and output, thereby improving fuel efficiency and performance.

A slang term for oversteer.

Measures the intake flow rate.

The bearings in an engine block that support the crankshaft.

A chassis layout that positions the engine behind the passenger compartment but ahead of the rear axle.

A type of body structure that derives its strength and rigidity from the use of thin, carefully shaped and joined panels, rather than from a framework of thick members. Also called "unit" or unitized construction.

A leaf spring with several leaves bundled together by steel bands.

A rear suspension consisting of at least four links, or "arms," and no struts. Because multilink suspensions assign specific wheel-locating duties to each element, they provide great flexibility for optimizing both ride and handling.

NAV: A system that uses the GPS Satellite System to provide navigation information that is constantly updated as the truck is in motion.

A cornering condition in which the front and rear slip angles are roughly the same. Although seemingly an ideal state of balance, perfect neutral steer is not as stable as slight understeer.

The Original Equipment Manufacturer is the company who made the component or, in the case of an assembly company, the company who assembled the assembled the component. Commonly, the OEM would be a company like Nissan, or Toyota.

The responsiveness and feel of the steering when the wheel is approximately centered. In a car with good on-center feel, the steering wheel tends to return to center when slightly deflected, assisting straight-line stability.

A technique in which the steering wheel is turned in the direction away from where the car is turning. Opposite lock is used to control a car when it is oversteering and its tail is swinging wide.

Any gearset in which the output shaft turns faster than the input shaft. Overdrive gears are used in most modern transmissions because they reduce engine rpm and improve fuel economy. Occasionally, a separate gearbox with an overdrive gearset is coupled to a conventional transmission.

The type of valvetrain arrangement in which the engine's camshaft(s) is in its cylinder head(s). When the camshaft(s) is placed close to the valves, the valvetrain components can be stiffer and lighter, allowing the valves to open and close more rapidly and the engine to run at higher rpm. In a single-overhead-cam (SOHC) layout, one camshaft actuates all of the valves in a cylinder head. In a double-overhead-camshaft (DOHC) layout, one camshaft actuates the intake valves, and one camshaft operates the exhaust valves.

A description of an engine whose bore is larger than its stroke.

A handling condition in which the slip angles of the rear tires are greater than the slip angles of the front tires. An oversteering car is sometimes said to be "loose," because its tail tends to swing wide.

A long lateral link that provides lateral location of a rigid axle. It usually sits roughly parallel to the axle, with one end attached to the body and the other attached to the axle.

Part-Time Four Wheel Drive: Refers to a four-wheel drive system that operates on-demand and drives all four wheels by locking front and rear axles together via a shift lever. It usually includes two speed ranges (Hi and Lo). Part-time 4WD systems must be operated in 2WD mode on dry pavement, as they're designed to be used only in specific situations when extra traction is required.

A combustion chamber whose upper surface resembles a shallow peaked roof. Usually used with four valves per cylinder.

The rotation of a car about a horizontal axis, which causes its nose or tail to bob up and down. Dive and squat are pitching motions.

A gearset in which all of the gears are in one plane, grouped around each other like the planets around the sun. The central gear is called the ""sun gear."" In mesh with it is a circular grouping of gears, called ""planet gears,"" mounted on a rotating carrier. The planet gears also engage teeth on the inner periphery of the ""ring gear."" By holding any one of the three gear elements motionless, different ratios can be produced between the other two. Planetary gearsets are common in automatic transmissions.

A chamber, located between the throttle body and the runners of an intake manifold, used to distribute the intake charge evenly and to enhance engine breathing.

When the gear position is in park or neutral position the switch is on.

The resistance of an object to rotational acceleration. When the mass of an object is distributed far from its axis of rotation, the object is said to have a high polar moment of inertia. When the mass distribution is close to the axis of rotation, it has a low polar moment of inertia. A mid-engined car has most of its mass within its wheelbase, contributing to a low polar moment of inertia, which, in turn, improves cornering turn-in.

A type of fuel injection with at least one injector mounted in the intake port(s) of each cylinder. Usually the injector is mounted on the air intake manifold close to the port. Port fuel injection improves fuel distribution and allows greater flexibility in intake-manifold design, which can contribute to improved engine breathing.

The unit of measurement for torque. One pound-foot is equal to the twisting force produced when a one-pound force is applied to the end of a one-foot-long lever.

The rate at which work is performed. Power is proportional to torque and rpm and is measured in horsepower

The subjectively defined rpm range over which an engine delivers a substantial fraction of its peak power. The power band usually extends from slightly below the engine's torque peak to slightly above its power peak.

An engine and transmission combination.

The aspect ratio of a tire.

A spring with an increasing spring constant. For example, if the first inch of spring motion requires 100 pounds of force, the second inch would require more than an additional 100 pounds, and the third inch would require still more. Progressive-rate springs become stiffer as they are compressed, unlike single-rate springs, which have a fixed spring rate.

the common unit of measurement for pressure. Normal atmospheric pressure at sea level is 14.7 psi.

The sensor is installed to the power steering High-pressure tube and detects a power steering load.

A slang term for understeer.

A general term for any rod that transfers force in compression. In a valvetrain, pushrods are used to transfer reciprocating motion from the cam followers to a more distant part of a valvetrain, typically the rocker arms.

A steering mechanism that consists of a gear in mesh with a toothed bar, called a ""rack."" The ends of the rack are linked to the steered wheels with tie rods. When the gear is rotated by the steering shaft, it moves the rack from side to side: turning the wheels.

The motion of a wheel that extends the suspension. The opposite of jounce.

A steering mechanism in which the steering shaft turns a worm gear that, in turn, causes a toothed metal block to move back and forth. Ball bearings in a recirculating track reduce friction between the worm gear and the block. As the block moves, its teeth rotate a gear connected to a steering arm, which then moves the steering linkage.

The maximum recommended revolutions per minute for an engine. In cars equipped with a tachometer: an instrument that measures engine rpm: the redline is usually indicated by, surprisingly enough, a red line. Some tachometers mark the redline with a colored sector. Others have two lines: the lower one marking the maximum allowable sustained engine rpm, the higher line indicating the absolute maximum rpm.

the state of a system in which an abnormally large vibration is produced in response to an external stimulus, occurring when the frequency of the stimulus is the same, or nearly the same, as the natural vibration frequency of the system.

resounding or echoing, as sounds: the resonant thundering of cannons being fired. Or, producing resonance; causing amplification or sustention of sound.

A measurement between the ground and some fixed reference point on a car's body (the reference point varies according to the whims of the particular automaker). This dimension can be used to measure the amount of suspension deflection or the height of the body from the ground.

A generally undesirable condition in which a wheel steers slightly as its suspension compresses or extends. Also called "bump steer."

Any gearset consisting of a small gear (the pinion gear) which turns a large-diameter annular gear (the ring gear).

The amount of power at the driving wheels needed to move a car down the road at a steady speed. This power varies according to the car's speed, aerodynamic drag, and mechanical friction, as well as the tires' rolling resistance. Road-load horsepower is distinct from engine power because the output of the engine is sapped by various mechanical losses between the engine's output at its flywheel and the driving wheels.

The ability of a car to grip the pavement. Technically described as "lateral acceleration," because cornering is actually a continuous deviation from a straight path. Measured in gs.

The rotation of a car's body about a longitudinal axis. Also less accurately called "sway" or "lean," it occurs in corners because the car's center of gravity is almost always higher than the axis about which it rotates.

Revolution Per Minute

A laterally aligned structural member that is attached to the body or the frame via vibration-absorbing rubber isolators. By bolting suspension or driveline components to such crossmembers, automotive engineers can reduce the transmission of noise and/or ride harshness to the body.

The professional association of transportation-industry engineers. The SAE sets most auto-industry standard for the testing, measuring, and designing of automobiles and their components.

The distance from the point where the steering axis intersects the ground to the longitudinal line that runs through the center of the tire's contact patch. Also called "steering offset."

As used by Car and Driver, the term "sedan" refers to a fixed-roof car with at least four doors or any fixed-roof two-door car with at least 33 cubic feet of rear interior volume, according to measurements based on SAE standard J1100.

A slightly curved leaf spring that is attached to a car's body at its ends and to a suspension component near its middle. One of the two body attachments is a shackle, which allows for changes in the spring's length as it flexes up and down.

An independent rear-suspension system in which each wheel hub is located only by a large, roughly triangular arm that pivots at two points. Viewed from the top, the line formed by the two pivots is somewhere between parallel and perpendicular to the car's longitudinal axis.

The numerical representation of a tire's aspect ratio. A 50-series tire has an aspect ratio of 0.50.

The mechanism in a transmission linkage that controls the motion of the gearshift lever. The shift gate is usually an internal mechanism; however, in some transmissions: including Ferrari five-speeds and Mercedes-Benz automatics : the shift gate is an exposed guide around the shift lever.

A device that converts motion into heat, usually by forcing oil through small internal passages in a tubular housing. Used primarily to dampen suspension oscillations, shock absorbers respond to motion; their effects, therefore, are most obvious in transient maneuvers. The following information is provided by Robo5: Shocks! Here are a couple links to some good info on the different types of shocks and how they are used, etc.... General info - http://www.4x4review.com/feature/shock-genius.asp Types of suspension - http://auto.howstuffworks.com/framed...ion_bible.html How leaf springs are tuned - http://www.off-road.com/toyota/proje...ing/index.html Bypass shocks - http://www.off-road.com/toyota/proje...cks/index.html How shocks are valved - http://www.off-road.com/toyota/proje...ing/index.html 10 things you need to know about shocks - http://www.4wheeloffroad.com/techart...ics/index.html Edit/Delete Message

A spring with a constant spring rate. For example, if a 100-pound force deflects the spring by one inch, an additional 100 pounds will deflect it one more inch, and so on until the spring either bottoms or fails.

A large area of smooth, flat pavement used for various handling tests. Roadholding is measured by defining a large-diameter circle (Car and Driver uses 300 feet) on the skidpad and measuring the fastest speed at which the car can negotiate the circle without sliding off.

The angular difference between the direction in which a tire is rolling and the plane of its wheel. Slip angle is caused by deflections in the tire's sidewall and tread during cornering. A linear relationship between slip angles and cornering forces indicates an easily controllable tire.

A slang for an automatic transmission.

Single overhead camshaft: an SOHC engine uses one camshaft in each cylinder head to operate both the exhaust valves and the intake valves.

A simple non-independent suspension, consisting of a rigid transverse member with wheel hubs solidly bolted to it. The axle can be attached to the body by leaf springs, or by a combination of suspension arms and links.

A particular kind of tube frame that consists exclusively of relatively short, small-diameter tubes. The tubes are welded together in a configuration that loads them primarily in tension and compression

An aerodynamic device that changes the direction of airflow in order to reduce lift or aerodynamic drag and/or improve engine cooling.

The opposite of dive, squat is the dipping of a car's rear end that occurs during hard acceleration. Squat is caused by a load transfer from the front to the rear suspension.

The line that intersects the upper and lower steering pivots on a steered wheel. On a car with a strut suspension, the steering axis is defined by the line through the strut mount on top and the ball joint on the bottom.

The general relationship between forces at the steering wheel and handling. Ideally, the steering effort should increase smoothly as the wheel is rotated away from center. In addition, the steering effort should build as the cornering forces at the steered wheels increase. Finally, the friction built into the steering mechanism should be small in comparison with the handling-related steering forces.

The relationship between yaw and the steering wheel's position and effort. All three should be proportional and should build up smoothly.

The group of design variables outside the steering mechanism that affect steering behavior, including camber, caster, linkage arrangement, ride steer, scrub radius, toe-in, and trail.

A subjective term that combines steering feel and steering gain.

Stoichiometric: Is the ideal ratio of combustion air and fuel for the combustion process. Ideal sought by the engines computer system. More info: http://www.engineeringtoolbox.com/stoichiometric-combustion-d_399.html Stoichiometric Combustion

The ability of a car to resist road irregularities and run in a straight line without steering corrections.

The distance between the extremes of a piston's travel in a cylinder

A suspension element in which a reinforced shock absorber is used as one of the wheel's locating members, typically by solidly bolting the wheel hub to the bottom end of the strut.

SUB: A term which is commonly referring to a Sub-Woofer which is a large speaker that is optimised for low frequency sound. Most SUBs operate at 100HZ or lower. Ususally requires a separate amplifier to handle the high power requirements of this speaker.

The space in the engine block under the crankshaft into which the oil drains from its various applications.

An air compressor used to force more air into an engine than it can inhale on its own. The term is frequently applied only to mechanically driven compressors, but it actually encompasses all varieties of compressors-including turbochargers.

A removable-roof body style popularized by Porsche that is similar to a convertible except that it incorporates a fixed, roll-bar-like structure running from side to side behind the front seats.

Part of the Brake system.

A housing containing a valve to regulate the airflow through the intake manifold. The throttle-body is usually located between the air cleaner and the intake plenum.

A form of fuel injection in which the injectors are located at the engine's throttle-body, thereby feeding fuel to more than one cylinder. Such an arrangement saves money by using fewer injectors; but because it routes both fuel and air through the intake manifold, it eliminates some of the tuning possibilities offered by port fuel injection.

The changes in the direction of a wheel that occur without driver steering input. Toe steer can be caused by ride steer or by deflections in suspension components caused by the stresses of cornering, accelerating, and/or braking on smooth and bumpy roads.

A lateral link in a multilink suspension designed to control a wheel's direction as the suspension moves up and down.

The intentional nonparallel orientation of opposite wheels. Toe-in is measured by subtracting the distance between the front edges of a pair of tires from the distance between the rear edges of the same pair of tires. The toe-in dimension is positive when the fronts of the tires are turned toward the center of the car.

The rotational equivalent of force, measured in pound-feet.

A particular kind of fluid coupling with a third element added to the usual input and output turbines. Called ""the stator,"" this additional element redirects the churning fluid against the output turbine, increasing torque. This torque increase, however, is achieved at the expense of rpm and efficiency.

A tendency for a car to turn in a particular direction when power is applied. Torque steer is common in front-drive cars because reaction forces created in the half-shafts can generate uneven steering forces in the front tires.

A spring consisting of a long solid or tubular rod with one end fixed to the chassis and the other twisted by a lever connected to the suspension.

Two potentiometers which transform the throttle valve position into an output voltage and sends this to the ECM. In addition, these sensors also detect the opening and closing speed of the throttle valve and feed the voltage signals to the ECM

An electronic control system that prevents wheelspin by detecting when a driven wheel is about to break traction, and then reducing engine power and/or applying the appropriate brakes to prevent it.

A driving technique in which the driver begins to brake before entering a turn and then continues to brake as he eases into the corner. As cornering forces build, the driver gradually feathers off the brakes: trading braking power for cornering grip. By increasing the vertical loading : and thus the traction: at the front tires, trail-braking can improve a car's turn-in.

A suspension element consisting of a longitudinal member that pivots from the body at its forward end and has a wheel hub rigidly attached to its trailing end. A sufficiently rigid trailing arm can provide all of a wheel's location. In that case it is similar to a semi-trailing arm, except that its pivot axis is exactly perpendicular to the car's longitudinal center line.

A suspension link that is aligned to resist longitudinal motions in a wheel; it is mounted to the chassis ahead of the wheel.

A transmission and a differential combined in one integrated assembly.

A gearbox with a number of selectable ratios, used to match the engine's rpm and torque to differing vehicle requirements.

The flexibility in the tire tread between the surface of the tread and the tire carcass. Snow tires, with their small, deep, unsupported tread blocks, have a large amount of tread squirm. Slick racing tires, which have no tread pattern, have very little squirm.

A car frame made up of rigid tubing welded together. Tube frames are easier to manufacture in small quantities than unitized frames.

The term that describes the convex curvature on the side of a car body.

Intake and exhaust systems that, by harnessing the pressure pulses and resonances inside the various passages and chambers of the intake and exhaust manifolds, increase the flow of intake charge into and out of the combustion chambers.

Within a turbocharger's operating range, lag is the delay between the instant a car's accelerator is depressed and the time the turbocharged engine develops a large fraction of the power available at that point in the engine's power curve.

A supercharger powered by an exhaust-driven turbine. Turbochargers always use centrifugal-flow compressors, which operate efficiently at the high rotational speeds produced by the exhaust turbine.

The moment of transition between driving straight ahead and cornering.

A joint that transmits rotary motion between two shafts that aren't in a straight line. Depending on its design, a universal joint can accommodate a large angular variation between its inputs and outputs. The simplest kind of universal joint, called a "Hooke joint," causes the output shaft to speed up and slow down twice for every revolution of the input shaft. This speed fluctuation increases with the angular difference between the shafts.

A handling condition in which the slip angle of the front tires is greater than the slip angle of the rears. An understeering car is sometimes said to push, because it resists turning and tends to go straight.

A type of body construction that doesn't require a separate frame to provide structural strength or support for the car's mechanical components. A unitized body can employ monocoque construction, or it can utilize strong structural elements as an integral part of its construction.

Utili-Track is a system of rails and moveable tie-down clamp assemblies that provide a versitile method of securing cargo in the bed of the pick-up.

Valve: The device in an engine that controls the flow of the intake charge or the exhaust. The typical internal combustion engine uses "poppet" valves. They look like a flat top mushroom with a very long stem. They are made from many different materials from steel to titanium. Rather exotic exhaust valves have the stem filled with SODIUM, a liquid metal to control the heat of the hot exhaust flow.

A high-rpm engine condition in which the valve lifters lose contact with the cam lobes because the valve springs are not strong enough to overcome the momentum of the various valvetrain components. The onset of valve float prevents higher-rpm operation. Extended periods of valve float will damage the valvetrain.

Also called a "valve follower": the cylindrically shaped component that presses against the lobe of a camshaft and moves up and down as the cam lobe rotates. Most valve lifters have an oil-lubricated hardened face that slides on the cam lobe. So-called "roller lifters," however, have a small roller in contact with the cam lobe: thereby reducing the friction between the cam lobe and the lifter.

The collection of parts that make the valves operate. The valvetrain includes the camshaft(s) and all related drive components, the various parts that convert the camshaft's rotary motion into reciprocating motion at the valves, and the valves and their associated parts.

resistance of a liquid to sheer forces (and hence to flow)

A particular kind of fluid coupling in which the input and output shafts mate with thin, alternately spaced discs in a cylindrical chamber. The chamber is filled with a viscous fluid that tends to cling to the discs, thereby resisting speed differences between the two shafts. Viscous couplings are used to limit the speed difference between the two outputs of a differential, or between the two axles of a car.

The signal is sent to the combination meter from the ABS acuator and electric unit by CAN communication line.

A valve used to limit the boost developed in a turbocharger. A waste gate operates by allowing some of the engine's exhaust flow to bypass the turbocharger's turbine section under certain conditions.

the distance, measured in the direction of propagation of a wave, between two successive points in the wave that are characterized by the same phase of oscillation.

An undesirable suspension characteristic in which a wheel (or several) moves up and down so violently that it actually leaves the ground. Wheel hop can be caused by many problems, including excessive unsprung weight, insufficient shock damping, or poor torsional axle control.

The rotation about a vertical axis that passes through the car's center of gravity.

A steering system whose geometry has a scrub radius of zero. This configuration minimizes the steering effects produced during acceleration (with front drive) or braking on varying traction surfaces.