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.
