GLOSSARY TERMS

U

U-Colt
U-shaped bolts to fit around the rear-axle housing for clamping the leaf spring to the housing.
U-Joint
A short term for universal joint.
U-Tube
A term used for manomometer.
Ultraviolet
An invisible spectrum with wavelengths shorter than visible light but longer than X-rays.
Ultraviolet Light
A light source used in non-destructive testing for cracks in metal parts.
Umbrella Seal
An umbrella-shaped valve stem seal used to direct oil away from the stem and guide.
Unburned Hydrocarbons
HC is a major pollutant in exhaust gases as a result of the partially unburned fuel after combustion.
Under-Dash Unit
A term used for hang on unit such as for a CB radio or other aftermarket accessory.
Under-Hood Lubrication Services
The work performed under the hood during a chassis lubrication such as lubricating the distributor, manifold heat-control valve, upper suspension, hood hinges and latch, checking the fluid level in the engine crankcase, brake master cylinder, radiator, battery, and power steering reservoir, plus inspecting belts and safety-related items.
Under-vehicle Lubrication Services
Work performed under the vehicle during a chassis lubrication such as changing oil and filter, checking or changing transmission fluid, and gear oil or differential gear oil, lubricating the suspension and steering system, universal joints, clutch and/or transmission linkage, front-wheel bearings, and inspection of safety-related items.
Undercarriage
The chassis of a vehicle.
Undercharge
An air-conditioning system that is short of refrigerant, resulting in improper cooling.
Underfill
A depression on the weld face or root surface extending below the adjacent surface of the base metal.
Underinflation
A condition with respect to tire inflation that decreases the rolling diameter and increases the contact area, which results in excessive sidewall flexing and tread wear causing excessive heat buildup, ultimately leading to severe tire damage.
Undersize (US)
A part of item that is smaller than that specified.
Underslung Suspension
A suspension system in which the spring is positioned under the axle.
Understaging
A vehicle placed at the beginning of a drag race, behind the normal starting point.
Understeer
A condition where the front of the vehicle tends to break out and slide toward the outside of a turn.
Undertread Compound
A blend of synthetic rubbers used in the material under the tire tread.
UNEP
An abbreviation for United Nations Environment Program.
Unequal A-Arms
A suspension system where one arm is larger than the other.
Unequal Length Control-Arm Suspension
Front suspension-control arms of unequal length to compensate for jounce and rebound.
Unfair Advantage
Not really unfair, the term given for that extra margin realized by a racing team with careful planning and attention to detail.
Unglued
An engine or transmission that has blown and is destroyed.
Unibody
A short term for unit body.
Unicast
A component or part cast as a single unit.
Unicast Rotor
Type of rotor used on many late-model cars having the rotor and hub cast as one integral component, often from gray iron rather than cast iron.
Uniform Pitch Spring
A valve spring having uniformly spaced coils.
Uniform Tire Quality Grading
Information required by the Department of Transportation to be molded into the sidewall of each tire to provide information relating to tread wear, traction, and temperature ratings.
Unit
One.
An assembly or device that can perform its function without outside interference or assistance.
Unit Body
A form of vehicle construction that includes the chassis, frame, and body in one unit.
Unit Cable
A cable having pairs of cables placed into groups (units) of a given quantity, then these groups form the core.
Unit Distributor
A breakerless ignition distributor used by General Motors containing the ignition coil, magnetic pickup coil, and timer core.
United Nations Environment Program (UNEP)
A program or agreement mandating the scheduled phaseout of CFC refrigerants.
United States Auto Club (USAC)
A sanctioning body for oval-track racing, such as the Indianapolis 500.
United States Customary System (USC measurements, USCS)
The type of measuring system used in the United States, such as gallon, inch, mile, and pounds.
Unitized Construction
A type of vehicle construction whereby the frame and body parts are welded together to form a single assembly.
Unitized Distributor
An electronic ignition-system magnetic-pulse distributor that combines the distributor, electronic module, pickup coil, cap, and coil into one compact assembly.
Universal Flexible Hose
A flexible radiator hose.
Universal Joint
A jointed connection in the drive line that permits the driving angle to change. Also known as U-joint.
Unleaded Fuel
Fuel that does not contain tetraethyl lead.
Unleaded Gasoline
Gasoline that contains less than 0.0018 ounces (0.05 grams) of lead per gallon (3.785 liters).
Unloader
A device linked to the throttle valve to open the choke valve when in the wide-open throttle position.
Unloading Solenoid
An electrically controlled valve for operating the throttling valve or bypass valve in some applications.
Unobtanium
A mythical alloy that is lighter, stronger, more flexible and, at the same time, more rigid than anything available.
Unsprung Weight
The vehicle weight not supported by the springs, including the steering knuckle, brake assembly, tire and wheel.
Updraft
A device or system having an upward airflow.
Updraft Carburetor
A carburetor having an updraft airflow.
Upper A-Arm
A term used for upper control arm.
Upper Control Arm
A front-suspension component bolted to the frame between the pivoting attachment point on the vehicle-frame crossmember and the upper ball joint, which is fastened to its outer end having bushings that are attached to the control arm.
Upper Radiator Hose
The radiator hose from the engine-coolant outlet to the radiator inlet.
Upshift
To shift from a lower gear to a higher gear ratio.
Upstream Blower
A blower arranged in the duct system so as to push air through the heater and/or air-conditioner core(s).
US
An abbreviation for undersize.
USA
An abbreviation for United States of America.
USAC
An abbreviation for United States Auto Club.
USC Measurements
A term used for United States Customary System.
The standard English system of measurement.
USCS
An abbreviation for United States Customary System.
Used-Car Price Guide
Either of several periodically published sources, generally available at libraries, for the used-car buyer or seller to determine the retail and wholesale value of a vehicle in the regional marketplace.
Used-Car Value Sources
A used-car price guide.
Ute
An abbreviation for utility vehicle.
Utility Body
A replacement for the cargo bed of a pickup truck that includes compartmental storage for parts and tools.
Utility Vehicle (ute)
A passenger-car-based pick up truck.
Utilization Equipment
Equipment that uses electric energy for mechanical, chemical, heating, lighting, or other useful purposes, such as an electric motor.
UV
An abbreviation for ultraviolet.
UV Light
That portion of the light spectrum beyond violet.
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