A-arm Triangular-shaped suspension component with two pivot points connected to the truck's frame and one point attached to the spindle.
ABS Antilock Braking System
add-a-leaf An extra spring leaf that is added to the spring pack.
after-cat system An aftermarket exhaust system that attaches to the outlet side of the catalytic converter and generally consists of a free-flow muffler, new tubing, and mounting equipment.
airbox Enclosed chamber that routes fresh air to the carburetor or intake manifold. Some trucks use an airbox with an integral filter; some use a remote filter at the airbox's intake duct.
air dam Full-width panel just below the bumper, designed to reduce or modify airflow under the truck, which improves aerodynamics but limits ground clearance.
air-down To lower the air pressure in tires. Airing down increases traction and smooths out the ride over rough terrain.
air/fuel mixture The ratio of air to gasoline that makes the fuel mixture. Theoretically, the perfect ratio is 14.7:1.
Air Locker A selectable locking differential manufactured by ARB that uses compressed air to engage the side gears.
all-wheel drive (AWD) A system in which all four wheels are driven but that lacks a multirange transfer case.
analog Gauge or display that shows a reading such as mph, rpm, or fuel level with a dial and moveable needle indicator.
anodize To apply a colored or clear oxide coating to an aluminum component through an electrical charge.
antisway bar Suspension component that prevents excessive side-to-side body sway. Syn. sway bar.
approach angle The maximum incline angle that a truck can climb or descend without hitting its front.
ARB 1. Air Resources Board. 2. Manufacturer of the Air Locker differential and other off-road products.
aspiration An engine's breathing system.
axle hop When a truck's axlehousing rotates opposite the direction as the tires under acceleration, then snaps back to its original position relative to the chassis. Sometimes, this motion is repetitive until the driver reduces the degree of acceleration. Syn. axlewrap.
axlehousing Exterior nonrotating housing that contains the axleshafts, differential, and the gears that drive the wheels.
axlewrap A condition where the rotational load from an axle is placed on the leaf spring. Springs are flexed into an "S" shape, storing spring energy until the tires slip.
backpressure Resistance to the free flow of exhaust gases.
backspacing The distance between a wheel's outer inboard edge and its mounting flange.
baffle 1. Plates, panels, or barriers inside a muffler that reduce sound. 2. A condition resulting from mysterious vehicle vibrations.
balance tube Short, laterally positioned pipe connecting the exhaust pipes on a dual-exhaust system. Used to equalize gas pressure between the two pipes.
ball joint A flexible joint consisting of a ball used in a socket, mainly in front suspensions because it can accommodate a wide range of angles.
BDC Bottom Dead Center, the lowest point of a piston's travel within the cylinder.
bead 1. The inner lip of a tire that attaches to the wheel. The exterior rubber bead conceals an embedded wire reinforcement. 2. In welding, a narrow half-round line where two pieces of metal have been joined.
bead lock A two-piece system that clamps the tire to the rim, especially helpful when airing down your tires for off-roading.
beater A truck that is rough or dented on the outside but might be mechanically sound. Syn. Bomber.
beefed-up 1. A 4x4 that is stronger than stock. 2. An after-dinner condition on the trail.
beltline 1. Body line running from front to back on a truck's side that visually separates the lower body from the lower edge of the greenhouse, the roof, and window assembly. 2. A measurement that increases as we get older.
bench race To talk about your truck and your driving feats as if they were fish stories.
bezel Trim ring, usually chromed or polished, that surrounds headlights or gauges.
bicycle To ride on either both right- or left-side wheels.
bikini top 1. A soft top that covers only the front seats and leaves the rear uncovered. 2. What many of us like our significant others to wear on the trail.
bellhousing Bell-shaped enclosure for the clutch and flywheel on a manual transmission or the flexplate and torque converter on an automatic transmission.
billet A part machined from a single piece of metal, not a casting.
bleed 1. To remove air in a hydraulic system by pumping out fluid. 2. What hands often do while working on trucks.
blip Quick touch of the throttle to momentarily rev an engine.
blower 1. Supercharger. 2. Ventilation system's motor.
blown engine 1. A seriously damaged engine. 2. A supercharged engine.
blow the doors off To defeat a competitor during a speed contest.
blueprint To rebuild an engine to its OE design specs, machining and checking the weight, size, and fit of each component against a factory blueprint.
bobbed The rear of the truck, SUV, of Jeep has been shortened, usually adjusted for better departure angle.
body roll 1. Tendency of a truck's body and chassis to lean toward the outside of a turn as the result of cornering forces. 2. The flesh that protrudes over our beltlines.
bog 1. Running an engine below its intended operating range by driving in too high of a gear for the speed or load. 2. The mud pit at a mud-bog race.
bogger 1. A vehicle built for mud racing. 2. One who mud-races. 3. (cap.) Type of tire
boiling the balonies Spinning the tires.
bolt-on Aftermarket part or component that can be installed without special modifications or major disassembly.
boneyard 1. Wrecking yard, junkyard, salvage yard. 2. The Back 40 of many 4x4 owner's homes.
boost The increase in intake pressure above atmospheric pressure provided by a supercharger or turbocharger. Boost is measured in psi.
bore 1. The diameter of a cylinder. 1. The act of machining a cylinder to fit larger pistons.
bored-and-stroked Combination of an enlarged cylinder bore and a lengthened piston stroke, resulting in an increase in overall engine displacement and power; rarely boring.
bottom end 1. The crankshaft, connecting rods, and main bearings of an engine. 2. Power at low engine speed.
bottom-out When the truck's suspension is fully compressed and its bumpstops won't allow further suspension travel.
boxed Strengthen a frame by adding a metal plate to an open-channel framerail or crossmember, thereby turning a three-sided framerail into a four-sided rail.
brake fade A loss of braking power, the result of the brakes' friction surface or the brake fluid becoming overheated.
broach to pierce or open, sometimes referring to a splined cut on a gear or flange.
bulletproof An allegedly indestructible truck or component.
bump 1. A horizontal obstacle. 2. To blip the accelerator. 3. To back off an obstacle, then hit it again with momentum.
bumpsteer A situation in which the steering jerks when a truck encounters a bump in the road. Bumpsteer is often caused by improper steering geometry.
bumpstick Camshaft
bumpstop Rubber or urethane block used to limit suspension compression travel.
burnout Deliberate spinning of the rear tires to heat and clean the tires' tread in preparation of maximum acceleration from a standing start. Can also be used to impress onlookers.
butt-scratcher A trail obstacle that scrapes on a truck's rear end.
cam 1. An eccentric device which converts rotating motion to reciprocating movement 2. Camshaft.
camber The tilt of the front tires toward or away from the center of the truck relative to vertical. When the top of the tire leans out the camber is positive; if the tire leans inward, camber is negative.
cam duration Amount of time, expressed in degrees of crankshaft rotation, that a cam holds open the intake or exhaust valves.
cam lift Distance, expressed in thousandths of an inch, at which a cam opens the valves.
candlepower A light brightness rating. Not all manufacturers use the same method to determine candlepower.
caster The fore or aft tilt of the steering axis relative to vertical. Lifting a truck can cause too much negative caster, which results in wandering.
catalytic converter An emissions-control device that routes exhaust gases through an oval-shaped canister filled with palladium and platinum pellets, thereby converting the toxic exhaust gases to water vapor, carbon dioxide, and less-toxic gases. Syn. cat.
CB Citizens band radio. A two-way radio commonly used for communication between trucks on the trail.
center disconnect A four-wheel-drive system that engages the front axles at an inboard location rather than the outboard hubs.
center of gravity The theoretical center of mass in a vehicle. It can change dramatically due to passenger load and cargo.
cherry Clean, in unusually fine shape.
CFM Cubic feet per minute, generally used to measure airflow through a port, intake manifold, or carburetor; a system used to determine carburetor and fuel-injection capacity.
chaindrive A system in which a chain and sprockets drive gears instead of the gears being meshed together.
chick-deflector Repulsively ugly vehicle. Ant. chick magnet
chicken-handle A handle for passengers to grab when the going gets rough; also known by other, unprintable names.
chip A computer's microprocessor, computer. A nick in the paint.
chirp the tires To shift quickly during hard acceleration so that the tires momentarily lose traction.
chunk 1. Slang for the ring-and-pinion gear assembly inside a differential housing. 2. When parts eject from their functional location.
clip A truck's entire front sheetmetal section, including the fenders, hood, and cowl.
coilover A suspension that uses shocks with an integral coil surrounding the shock body, often used with custom-fabricated multilink suspensions because they offer the advantages of easy preload and ride-height adjustments, lots of wheel travel, and accurate spring dampening rates.
collector Device that collects exhaust gases from the exhaust manifold's (or header's) primary tubes and routes them into a single-exhaust pipe.
combustion chamber A cavity within the cylinder head(s), just above the piston(s), where combustion takes place.
compression ratio The ratio of cylinder volume with the piston at BDC to the volume remaining in the cylinder chamber when the piston reaches TDC. The greater the difference, the higher the compression ratio, generally producing more power. If the compression ratio is too high, however, it can cause detonation and an increase in pollutants.
contact patch Portion of a tire tread in contact with the road surface.
Cornbinder Slang for any 4x4 made by InternationalHarvester because the company is known for making farm equipment. Syn. 'Binder.
crank it 1. To turn the steering wheel hard left or right. 2. To start the engine.
crankshaft Shaft with large, U-shaped cranks that are connected to the pistons' connecting rods and transforms the pistons' reciprocal motion to a rotational motion, which powers the drivetrain. Syn. crank.
crawl-ratio The lowest gear ratio in the truck, found by multiplying the First gear ratio of the tranny by the low-range gear ratio of the transfer case by the axle gear ratio.
cross-drilled crank Crankshaft with additional lubrication holes drilled opposite the existing main journal oil feed holes, providing improved high-rpm-bearing lubrication.
curb weight Total weight of a truck with the fuel tank full, the engine oil at its proper level, and the cooling system full, but without a payload or passengers.
CV joint Constant velocity joint, two U-joints in tandem or a Rzeppa joint which allows for increased angularity of driveline components. Commonly found on front driveshafts and front-drive axles.
cylinder head The part of an engine that contains the valvetrain and the combustion chambers and covers the tops of the cylinders and pistons.