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Parent Category: Maintenance Guide

Category: Engine Guide

Automotive terms Modern (U-V)

Automotive Technical terms and abbreviations overview used in the industry, Guide and explanations.

The following are examples of Mid Modern technical terms recommended for general use worldwide. For in-depth specific terms also see terms for historic vintage and specific areas such as Paint.

U-JOINT (UNIVERSAL JOINT):
A flexible coupling in the drive train that allows the driveshafts or axle shafts to operate at different angles and still transmit rotary power.

UNDERSTEER:
The tendency of a car to continue straight ahead while negotiating a turn. UNIT BODY: Design in which the car body acts as the frame.

UNLEADED FUEL:
Fuel which contains no lead (a common gasoline additive), The presence of lead in fuel will destroy the functioning elements of a catalytic converter, making it useless.

UNSPRUNG WEIGHT:
The weight of car components not supported by the springs (wheels, tires, brakes, rear axle, control arms, etc.).

UPSHIFT:
A shift that results in a decrease in torque ratio and an increase in speed.

VACUUM:
A negative pressure; any pressure less than atmospheric
pressure.

VACUUM ADVANCE:
A device which advances the ignition timing in response to increased engine vacuum.

VACUUM GAUGE:
An instrument used for measuring the existing vacuum in a vacuum circuit or chambec The unit of measure is inches (of mercury in a barometer).

VACUUM MODULATOR:
Generates a hydraulic oil pressure in response to the amount of engine vacuum.

VALVES:
Devices that can open or close fluid passages in a hydraulic system and are used for directing fluid flow and controlling pressure.

VALVE BODY ASSEMBLY:
The main hydraulic control assembly of the transmission/transaxle that contains numerous valves, check balls, and
other components to control the distribution of pressurized oil throughout the transmission,

VALVE CLEARANCE:
The measured gap between the end of the valve
stem and the rocker arm, cam lobe or follower that activates the valve.

VALVE GUIDES:
The guide through which the stem of the valve passes, The guide is designed to keep the valve in proper alignment.

VALVE LASH (clearance):
The operating clearance in the valve train.

VALVE TRAIN:
The system that operates intake and exhaust valves, consisting of camshaft, valves and springs, lifters, pushrods and rocker arms.

VAPOR LOCK:
Boiling of the fuel in the fuel lines due to excess heat. This will interfere with the flow of fuel in the lines and can completely stop the flow. Vapor lock normally only occurs in hot weather.

VARIABLE DISPLACEMENT (VARIABLE CAPACITY) VANE PUMP:
Slipper-type vanes, mounted in a revolving rotor and contained within the bore of a movable slide, capture and then force fluid to flow. Movement of the slide to various positions changes the size of the vane chambers and the amount of fluid flow. Note: GM refers to this pump design as variable displacement, and Ford terms it variable capacity.

VARIABLE FORCE SOLENOID (VS):
Commonly referred to as the electronic pressure control (EPC) solenoid, it replaces the cable/linkage style of TV system control and is integrated with a spool valve and spring assembly to control pressure. A variable computer-controlled current flow varies the internal force of the solenoid on the spool valve and resulting control pressure.

VARIABLE ORIFICE THERMAL VALVE:
Temperature-sensitive hydraulic oil control device that adjusts the size of a circuit path opening. By altering the size of the opening, the oil flow rate is adapted for cold to hot oil viscosity changes.

VARNISH:
Term applied to the residue formed when gasoline gets old and stale.

VCM:
See Electronic Control Unit (ECU).

VEHICLE SPEED SENSOR (VSS):
Provides an electrical signal to the computer module, measuring vehicle speed, and affects the torque converter clutch engagement and release.

VESPEL SEALING RINGS:
Hard Plastic material that produces excellent sealing in dynamic settings. These rings are found in late versions of the 4T60 and in all 4T60-E and 4T80-E transaxles.

VISCOSITY:
The ability of a fluid to flow. The lower the viscosity rating, the easier the fluid will flow. 10 weight motor oil will flow much easier than 40 weight motor oil.

VISCOSITY INDEX IMPROVERS:
Keeps the viscosity nearly constant with changes in temperature. This is especially important at low tempera-tures, when the oil needs to be thin to aid in shifting and for cold-weather starting. Yet it must not be so thin that at high temperatures it will cause excessive hydraulic leakage so that pumps are unable to maintain the
proper pressures.

VISCOUS CLUTCH:
A specially designed torque converter clutch apply plate that, through the use of a silicon fluid, clamps smoothly and absorbs torsional vibrations.

VOLT:
Unit used to measure the force or pressure of electricity. It is defined as the pressure

VOLTAGE:
The electrical pressure that causes current to flow. Voltage is measured in volts (V).

VOLTAGE, APPLIED:
The actual voltage read at a given point in a circuit. It equals the available voltage of the power supply minus the losses in the circuit up to that point.

VOLTAGE DROP:
The voltage lost or used in a circuit by normal loads such as a motor or lamp or by abnormal loads such as a poor (high-resistance) lead or terminal connection.

VOLTAGE REGULATOR:
A device that controls the current output of the alternator or generator.

VOLTMETER:
An instrument used for measuring electrical force in units called volts. Voltmeters are always connected parallel with the circuit being tested.

VORTEX FLOW:
The crosswise or circulatory flow of oil between the blades of the members caused by the centrifugal pumping action of the impeller.

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Parent Category: Maintenance Guide

Category: Engine Guide

Automotive terms Modern (W-Z)

Automotive Technical terms and abbreviations overview used in the industry, Guide and explanations.

The following are examples of Mid Modern technical terms recommended for general use worldwide. For in-depth specific terms also see terms for historic vintage and specific areas such as Paint.

WANKEL ENGINE:
An engine which uses no pistons. In place of pistons, triangular-shaped rotors revolve in specially shaped housings.

WATER PUMP:
A belt driven component oi the cooling system that mounts on the engine, circulating the coolant under pressure.

WATT:
The unit for measuring electrical power. One watt is the product of one ampere and one volt (watts equals amps times volts). Wattage is the horsepower of electricity (746 waits equal one horsepower).

WHEEL ALIGNMENT:
Inclusive term to describe the front end geometry (caster, camber, toe-in/out).

WHEEL CYLINDER:
Found in the automotive drum brake assembly, it is a device, actuated by hydraulic pressure, which, through internal pistons, pushes the brake shoes outward against the drums.

WHEEL WEIGHT:
Small weights attached to the wheel to balance the wheel and tire assembly. Out-of-balance tires quickly wear out and also
give erratic handling when installed on the front.

WHEELBASE:
Distance between the center of front wheels and the center of rear wheels.

WIDE OPEN THROTTLE (WOT):
Full travel of accelerator pedal.

WORK:
The force exerted to move a mass or object. Work involves motion; if a force is exerted and no motion takes place, no work is done.
Work per unit of time is called power. Work = force x distance = ft. lbs. 33,000 ft. lbs. in one minute = 1 horsepower

ZERO-THROTTLE COAST DOWN:
A full release of accelerator pedal while vehicle is in motion and in drive range.

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Parent Category: Maintenance Guide

Category: Engine Guide

Automotive terms Modern (R)

Automotive Technical terms and abbreviations overview used in the industry, Guide and explanations.

The following are examples of Mid Modern technical terms recommended for general use worldwide.For in-depth specific terms also see terms for historic vintage and specific areas such as Paint.

RACE:
The surface on the inner or outer ring of a bearing on which the balls, needles or rollers move.

RACK AND PINION:
A type of automotive steering system using a pinion gear attached to the end of the steering shaft. The pinion meshes with a long rack attached to the steering linkage.

RADIAL TIRE:
Tire design which uses body cords running at right angles to the center line of the tire, Two or more belts are used to give tread strength.Radials can be identified by their characteristic sidewall bulge.

RADIATOR:
Part of the cooling system for a water-cooled engine, mounted in the front of the vehicle and connected to the engine with rubber hoses, Through the radiator, excess combustion heat is dissipated into the atmosphere through forced convection using a water and glycol based mixture that circulates through, and cools, the engine,

RANGE REFERENCE AND CLUTCH/BAND APPLY CHART:
A guide that shows the application of clutches and bands for each gear, within the selector range positions. These charts are extremely useful for understanding how the unit operates and for diagnosing malfunctions.

RAVIGNEAUX GEARSET:
A compound planetary gearset that features matched dual planetary pinions (sets of two) mounted in a single planet
carrier. Two sun gears and one ring mesh with the carrier pinions.

REACTION MEMBER:
The stationary planetary member, in a planetary gearset, that is grounded to the transmission/transaxle case through the use of friction and wedging devices known as bands, disc clutches, and one-way clutches.

REACTION PRESSURE:
The fluid pressure that moves a spool valve against an opposing force or forces; the area on which the opposing force acts. The opposing force can be a spring or a combination of spring force and auxiliary hydraulic force.

REACTOR, TORQUE CONVERTER:
The reaction member of a fluid torque converter, more commonly called a stator. (See stator.)

REAR MAIN OIL SEAL:
A synthetic or rope-type seal that prevents oil from leaking out of the engine past the rear main crankshaft bearing.

RECIRCULATING BALL:
Type of steering system in which recirculating steel balls occupy the area between the nut and worm wheel, causing a reduction in friction.

RECTIFIER:
A device (used primarily in alternators) that permits electrical current to flow in one direction only.

REDUCTION:
(See gear reduction.)

REGULATOR VALVE:
A valve that changes the pressure of the oil in a hydraulic circuit as the oil passes through the valve by bleeding off (or exhausting) some of the volume of oil supplied to the valve.

REFRIGERANT 12 (R-12) or 134 (R-134):
The generic name of the refrigerant used in automotive air conditioning systems.

REGULATOR:
A device which maintains the amperage and/or voltage levels of a circuit at predetermined values.

RELAY:
A switch which automatically opens and/or closes a circuit.

RELAY VALVE:
A valve that directs flow and pressure. Relay valves simply connect or disconnect interrelated passages without restricting the fluid flow or changing the pressure.

RELIEF VALVE:
A spring-loaded, pressure-operated valve that limits oil pressure buildup in a hydraulic circuit to a predetermined maximum value.

RELUCTOR:
A wheel that rotates inside the distributor and triggers the release of voltage in an electronic ignition.

RESERVOIR:
The storage area for fluid in a hydraulic system; often called a sump.

RESIN:
A liquid plastic used in body work.

RESIDUAL MAGNETISM:
The magnetic strength stored in a material after a magnetizing field has been removed.

RESISTANCE:
The opposition to the flow of current through a circuit or electrical device, and is measured in ohms. Resistance is equal to the voltage divided by the amperage.

RESISTOR SPARK PLUG:
A spark plug using a resistor to shorten the spark duration. This suppresses radio interference and lengthens plug life.

RESISTOR:
A device, usually made of wire, which offers a preset amount of resistance in an electrical circuit.

RESULTANT FORCE:
The single effective directional thrust of the fluid force on the turbine produced by the vortex and rotary forces acting in different planes.

RETARD:
Set the ignition timing so that spark occurs later (fewer degrees before TDC).

RHEOSTAT:
A device for regulating a current by means of a variable resistance.

RING GEAR:
The name given to a ring-shaped gear attached to a differential case, or affixed to a flywheel or as part of a planetary gear set.

ROADLOAD:
grade.

ROCKER ARM:
A lever which rotates around a shaft pushing down (opening) the valve with an end when the other end is pushed up by the pushrod. Spring pressure will later close the valve.

ROCKER PANEL:
The body panel below the doors between the wheel
opening.

ROLLER BEARING:
A bearing made up of hardened inner and outer races between which hardened steel rollers move.

ROLLER CLUTCH:
A type of one-way clutch design using rollers and springs mounted within an inner and outer cam race assembly.

ROTARY FLOW:
The path of the fluid trapped between the blades of the members as they revolve with the rotation of the torque converter cover (rotational inertia), ROTOR: (1,) The disc-shaped part of a disc brake assembly, upon which
the brake pads bear; also called, brake disc. (2.) The device mounted atop the distributor shaft, which passes current to the distributor cap tower contacts.

ROTARY ENGINE:
see wankel engine.

RPM:
Revolutions per minute (usually indicates engine speed).

RTV:
A gasket making compound that cures as it is exposed to the atmosphere. It is used between surfaces that are not perfectly machined to one another, leaving a slight gap that the RTV fills and in which it hardens. The letters RTV represent room temperature vulcanizing.

RUN-ON:
Condition when the engine continues to run, even when the key is turned off. See dieseling.

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Parent Category: Maintenance Guide

Category: Engine Guide

Automotive terms Modern (S)

Automotive Technical terms and abbreviations overview used in the industry, Guide and explanations.

The following are examples of Mid Modern technical terms for the letter S recommended for general use worldwide. For in-depth specific terms also see terms for historic vintage and specific areas such as Paint.

SEALED BEAM:
A automotive headlight. The lens, reflector and filament from a single unit.

SEATBELT INTERLOCK:
A system whereby the car cannot be started unless the seatbelt is buckled.

SECONDARY CIRCUIT:
The high voltage side of the ignition system, usually above 20,000 volts. The secondary includes the ignition coil, coil wire, distributor cap and rotor, spark plug wires and spark plugs.

SELF-INDUCTION:
The generation of voltage in a current-carrying wire by changing the amount of current flowing within that wire.

SEMI-CONDUCTOR:
A material (silicon or germanium) that is neither a good conductor nor an insulator; used in diodes and transistors.

SEMI-FLOATING AXLE:
In this design, a wheel is attached to the axle shaft, which takes both drive and cornering loads. Almost all solid axle passenger cars and light trucks use this design.

SENDING UNIT:
A mechanical, electrical, hydraulic or electromagnetic device which transmits information to a gauge.

SENSOR:
Any device designed to measure engine operating conditions or ambient pressures and temperatures. Usually electronic in nature and designed to send a voltage signal to an on-board computer, some sensors may operate as a simple on/off switch or they may provide a variable voltage signal (like a potentiometer) as conditions or measured parameters change.

SERIES CIRCUIT:
(See circuit, series.)

SERPENTINE BELT:
An accessory drive belt, with small multiple v-ribs, routed around most or all of the engine-powered accessories such as the alternator and power steering pump. Usually both the front and the back side of the belt comes into contact with various pulleys,

SERVO:
In an automatic transmission, it is a piston in a cylinder assembly that converts hydraulic pressure into mechanical force and movement; used for the application of the bands and clutches.

SHIFT BUSYNESS:
When referring to a torque converter clutch, it is the frequent apply and release of the clutch plate due to uncommon driving conditions.

SHIFT VALVE:
Classified as a relay valve, it triggers the automatic shift in response to a governor and a throttle signal by directing fluid to the appropriate band and clutch apply combination to cause the shift to occur.

SHIM:
Spacers of precise, predetermined thickness used between parts to establish a proper working relationship.

SHIMMY:
Vibration (sometimes violent) in the front end caused by misaligned front end, out of balance tires or worn suspension components.

SHORT CIRCUIT:
An electrical malfunction where current takes the path of least resistance to ground (usually through damaged insulation). Current flow is excessive from low resistance resulting in a blown fuse.

SHUDDER:
Repeated jerking or stick-slip sensation, similar to chuggle but more severe and rapid in nature, that may be most noticeable during certain ranges of vehicle speed; also used to define condition after converter clutch engagement.

SIMPSON GEARSET:
A compound planetary gear train that integrates two simple planetary gearsets referred to as the front planetary and the rear planetary.

SIPPING
Tire process to improve traction across rubber surface by cutting thin slits to improve traction in wet .

SINGLE OVERHEAD CAMSHAFT:
see overhead camshaft.

SKIDPLATE:
A metal plate attached to the underside of the body to protect the fuel tank, transfer case or other vulnerable parts from damage.

SLAVE CYLINDER:
In automotive use, a device in the hydraulic clutch system which is activated by hydraulic force, disengaging the clutch.

SLIPPING:
Noticeable increase in engine rpm without vehicle speed increase; usually occurs during or after initial clutch or band engagement.

SLUDGE:
Thick, black deposits in engine formed from dirt, oil, water, etc. It is usually formed in engines when oil changes are neglected.

SNAP RING:
A circular retaining clip used inside or outside a shaft or part to secure a shaft, such as a floating wrist pin.

SOFT:
Slow, almost unnoticeable clutch apply with very little shift feel.

SOFTCODES:
DTCs that have been set into the PCM memory but are not present at the time of testing; often referred to as history or intermittent codes.

SOHC:
Single overhead camshaft.

SOLENOID:
An electrically operated, magnetic switching device.

SPALLING:
A wear pattern identified by metal chips flaking off the hardened surface. This condition is caused by foreign particles, overloading situations, and/or normal wear.

SPARE
Term for spare tire to replace a flat tire normally hidden under floor.

SPARK PLUG:
A device screwed into the combustion chamber of a spark ignition engine. The basic construction is a conductive core inside of a ceramic insulator, mounted in an outer conductive base. An electrical charge from the spark plug wire travels along the conductive core and jumps a preset air gap to a grounding point or points at the end of the conductive base. The resultant spark ignites the fuel/air mixture in the combustion chamber.

SPARK-IGNITION
Ignition system. where the combustion process of the air-fuel mixture is ignited from a spark plug.

SPECIFIC GRAVITY (BATTERY):
The relative weight of liquid (battery electrolyte) as compared to the weight of an equal volume of water.

SPEEDOMETER
The speedometer is a gauge that measures and displays the speed of a vehicle early vehicles analogue and more modern often electric.

SPLINES:
Ridges machined or cast onto the outer diameter of a shaft or inner diameter of a bore to enable parts to mate without rotation.

SPLIT TORQUE DRIVE:
In a torque converter, it refers to parallel paths of torque transmission, one of which is mechanical and the other hydraulic.

SPONGY PEDAL:
A soft or spongy feeling when the brake pedal is depressed. It is usually due to air in the brake lines.

SPOOLVALVE:
A precision-machined, cylindrically shaped valve made up of lands and grooves. Depending on its position in the valve bore, various interconnecting hydraulic circuit passages are either opened or closed.

SPRAG CLUTCH:
A type of one-way clutch design using cams or contoured-shaped sprags between inner and outer races. (See one-way clutch.)

SPRUNG WEIGHT:
The weight of a car supported by the springs.

SQUARE-CUT SEAL:
Molded synthetic rubber seal designed with a square- or rectangular-shaped cross-section. This type of seal is used for both dynamic and static applications.
SRS: Supplemental restraint system

STABILIZER (SWAY) BAR:
A bar linking both sides of the suspension. It resists sway on turns by taking some of added load from one wheel and putting it on the other.

STAGE:
The number of turbine sets separated by a stator. A turbine set may be made up of one or more turbine members. A three-element converter is classified as a single stage.

STALL:
In fluid drive transmission/transaxle applications, stall refers to engine rpm with the transmission/transaxle engaged and the vehicle stationary; throttle valve can be in any position between closed and wide open.

STALL SPEED:
In fluid drive transmission/transaxle applications, stall speed refers to the maximum engine rpm with the transmission/transaxle engaged and vehicle stationary, when the throttle valve is wide open. (See stall; stall test.)

STALL TEST:
A procedure recommended by many manufacturers to help determine the integrity of an engine, the torque converter stator, and certain clutch and band combinations. With the shift lever in each of the forward and reverse positions and with the brakes firmly applied, the accelerator pedal is momentarily pressed to the wide open throttle (WOT) position. The engine rpm reading at full throttle can provide clues for diagnosing the condition of the items listed above.

STALL TORQUE:
The maximum design or engineered torque ratio of a fluid torque converter, produced under stall speed conditions. (See stall speed.)

STARTER:
A high-torque electric motor used for the purpose of starting the engine, typically through a high ratio geared drive connected to the fly-wheel ring gear.

STATIC:
A Sealing application in which the parts being sealed do not

STATOR (REACTOR):
The reaction member Of a fluid torque converter that changes the direction of the fluid as it leaves the turbine to enter the impeller vanes. During the torque multiplication phase, this action assists the impeller's rotary force and results in an increase in torque.

STEERING COLUMN
The steering column also performs the following secondary functions: provide mounting switch locations, or in some vehicles the gear selector.

STEERING GEOMETRY:
Combination of various angles of suspension components (caster, camber, toe-in); roughly equivalent to front end align

STEERING LOCK
An anti-theft device. fitted to the steering column disengaged by the ignition key or in modern cars electronically.

STEERING WHEEL
Normally a hand-held wheel to control vehicles. Makes the steering system responds to the driver inputs.

STRAIGHT ENGINE
The straight engine has all the cylinders aligned in a row.(also called inline engine)

STRAIGHT WEIGHT:
Term designating motor oil as suitable for use within a narrow range of temperatures. Outside the narrow temperature range its flow characteristics will not adequately lubricate.

STROKE:
The distance the piston travels from bottom dead center to top dead center.

SUBFRAME:
The structural component of a vehicle, a separate structure within a larger frame or body to spread chassis loads.

SUBSTITUTION:
Replacing one part suspected of a defect with a like part of known quality.

SUMP:
The storage vessel or reservoir that provides a ready source of fluid to the pump. In an automatic transmission, the sump is the oil pan. All fluid eventually returns to the sump for recycling into the hydraulic system.

SUN GEAR:
In a planetary gearset, it is the center gear that meshes with a cluster of planet pinions.

SUN VISOR
To help shade from the glare of sunlight this interior component above the windshield often hinged and adjustable and option on early transport.

SUPERCHARGER:
An air pump driven mechanically by the engine through belts, chains, shafts or gears from the crankshaft. Two general types of supercharger are the positive displacement and centrifugal type, which pump air in direct relationship to the speed of the engine.

SUPPLEMENTAL RESTRAINT SYSTEM:
see air bag.

SURGE:
Repeating engine-related feeling of acceleration and deceleration that is less intense than chuggle.

SUSPENSION
General term for the complete suspension system including shock absorbers springs and all components.

SWITCH:
A device used to open, close, or redirect the current in an electrical circuit.

SYNCHROMESH:
A manual transmission/transaxle that is equipped with devices (synchronizers) that match the gear speeds so that the trans-
mission/transaxle can be downshifted without clashing gears.

SYNTHETIC OIL:
Non-petroleum based oil.