| U
| Uranium An element with the atomic number of 92 |
| U-bolt
| 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. |
| U.S.
| An acronym for United States. |
| u/
| Under |
| UART
| Universal Asynchronous Receive and Transmit. A type of data stream used on non-OBD-II diagnostic systems. UART toggles between 5 volts (positive) and 0 volts |
| UDOT
| Utah Department of Transportation |
| UIM
| Universal ignition module |
| ultrahigh frequency (UHF)
| The band of signal frequencies falling between 300 and 3000 MHz. |
| ultraviolet
| An invisible spectrum with wavelengths shorter than visible light b longer than X-rays about 200 to 4000 angstrom units. |
| 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. |
| UNC
| An acronym for Unified National Coarse. Identifying a standard thread pitch and count. |
| 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 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 ans/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 acronym 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. |
| UNF
| an acronym for Unified national fine. Identifying a standard thread pitch and count. |
| 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 man late-model cars having the rotor and hub cast as one integral component, often from gray iron rather than cast iron. |
| unidirectional rotor
| A rotor with cooling fins that are curved or formed at a angle to the hub center to increase cooling airflow. Because the fins only work properly when the rotor turns in one direction, unidirectional rotors cannot be interchanged from right to left . |
| unidirectional tread pattern
| A tire tread pattern that can be rotated only in one direction. Thus left to right rotation cannot be done. |
| 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
| 1. One. 2. 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 joint 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. |
| unscheduled deployment
| A term used when referring to air bag system that could be set off without the vehicle being involved in a crash. |
| 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. |
| UPS
| an acronym for Uninterruptible Power Supply; a power supply that includes a battery to maintain power in the event of a power outage. |
| upshift
| 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). |
| URL
| an acronym for Uniform Resource Locator; the global address of documents and other resources on the World Wide Web. |
| US
| An acronym for undersize. |
| USA
| An acronym for United States of America. |
| USAC
| An acronym for United States Auto Club. |
| USC measurements
| 1. A term used for United States Customary System. 2. The standard English system of measurement. |
| USCS
| An acronym 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. |
| user friendly
| A computer, computer program, or equipment that is easy to use by an inexperienced person. |
| username
| A name used to gain access to a computer system |
| ute
| An acronym 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. |
| UTQG
| 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. |
| UV
| An acronym for ultraviolet. |
| UV light
| that portion of the light spectrum beyond violet. |
Auto & Car Glossary
