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Off-Road Glossary

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The most comprehensive list of off-road definitions, terms, and lingo that all truck & Jeep owners use while off-road, in the shop, or at shows.  If you have a term or lingo you would like to share, let us know by emailing us at


A-Arm - Triangular-shaped suspension component with two pivot points connected to the truck's frame and one point attached to the spindle.

ABS - abbreviation for Antilock Braking System
Ackerman Angle - is the turning angle of an inside wheel that is different from the turning angle of the outside wheel to account for the fact that the inside wheel travels a shorter path. This difference, which is an engineered value, is called the Ackerman angle. The prevents the front end from “jumping” or one side dragging.  Sometime referred to as “toe-out turns”


Add-a-Leaf - a simple and less expensive way for lifting a vehicle equipped with leaf springs. An extra leaf spring is inserted into the leaf spring pack to achieve a higher ride height than the stock OEM setup 

After-Cat System - is 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 - is an 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 - is a 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-Down Tires - Usually done before an off-road excursion and consist of lowering the air pressure in your tires when a truck or Jeep owner air downs their tires to a lower P.S.I. pressure than what is stated in the owner’s manual or the door-jamb sticker for road use. This can be done by using the back end of a tire pressure gauge, an off-road-specific air-down kit, or your fingernail!  It is important to air down all four tires to a matching PSI that is lower than the recommended level. It improves traction and can reduce wear on the suspension, including the shocks.

Air/Fuel Mixture - the ratio of air to gasoline that makes the fuel mixture. Many experts claim the perfect air to fuel ratio is 14.7:1.

Air Locker - is a selectable locking differential manufactured by ARB that uses compressed air to engage the side gears.

All-Wheel Drive (AWD) - a vehicle drive-train that is engineered that  all four wheels are driven but that lacks a multi-range transfer case.

Amp Draw - is the amount of ampere-hours consumed by a piece of electrical equipment such as a winch during operation. Another example is a measurement of the power being consumed by a blower motor to move the air through your HVAC system or the measurement of the energy a battery can hold and supply at a specific voltage.

Analog - is a gauge or display that shows a reading such as mph, rpm, or fuel level with a dial and moveable needle indicator vs digital.

Anodize - is to apply a colored or clear oxide coating to an aluminum component through an electrical charge.

Anti-Sway Bar - is a suspension component that prevents excessive side-to-side body sway usually in trucks, Jeeps, and SUV’s that regularly go on off-road surfaces.

Approach Angle - is the steepest angle a vehicle can climb or descend before its front bumper, body, chassis, or equipment mounted there make contact with the ground. Approach angles can be improved for off-roading with the installation of various lift kits to increase ride height. This is the maximum angle of clearance a vehicle has when climbing a hill or approaching another obstacle. It’s the angle between the ground and the line drawn between the front tire and the lowest-hanging part of the vehicle (often the bumper). Approach angle is very important to know - if you exceed the approach angle, it almost always causes damage to your front end.

ARB - stands for Air Resources Board which is a clean-air board that addresses vehicle emissions.  California has one of the largest

ARB’s called the CARB or California Air Resource Board.  ARB is also an off-road product manufacturer.

Articulation - or “flex” is a term that applies to how much vertical movement the axle and wheel have on off-road vehicles. It is often also referred to as “wheel travel”. The more articulation your truck or Jeep has, the better rock climber it will be because the wheels have more up and down motion. A suspension's capacity to combine compression ("bump") and droop on one axle over uneven terrain is the best definition of articulation. If your truck or Jeep body remains generally level while the axles work at extreme angles to navigate uneven ground, your articulation rocks...literally! 

Aspiration - any vehicle’s engine breathing system.

Axle Hop - is when a truck's axle-housing 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. Sometimes called axle-wrap but see the correct definition below.

Axle Housing - is the exterior non-rotating housing that contains the axle shafts, differential, and the gears that drive the wheels on any vehicle.

Axle Wrap - is 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.


Back-pressure - is resistance to the free flow of exhaust gases.


Back-spacing - is the distance between a wheel's outer inboard edge and its mounting flange.


Baffle - consist of either plates, panels, or barriers inside a muffler that reduce sound. 


Balance Tube - is a short, laterally positioned pipe connecting the exhaust pipes on a dual-exhaust system. Used to equalize gas pressure between the two pipes.


Ball Joint - is a flexible joint consisting of a ball used in a socket, mainly in front suspensions because it can accommodate a wide range of angles.


Basket Case - is an engine or vehicle that is in a lot of pieces


BDC - stands for Bottom Dead Center which is the lowest point of a piston's travel within a cylinder in an engine.


Bead - The inner lip of a tire that attaches to the wheel. The exterior rubber bead conceals an embedded wire reinforcement. Or, in welding, a narrow half-round line where two pieces of metal have been joined.


Bead Lock - is a two-piece system that clamps the tire to the rim, especially helpful when airing down your tires for off-roading.

Bead-Lock Wheel - A bead lock is a tire/wheel setup where the bead of the tire has been secured to the wheel. This is often done at a tire shop with a special mechanical tool. Bead lock wheels are easy to distinguish by the ring of bolts around the circumference of the wheel that keeps the tire in place. The benefits for doing this is you are able to air down the tire to a much lower pressure without the tire slipping off the rim, which maximizes traction.A series of metal reinforcement rings that clamp a tire to a rim to provide greater resistance from the tire popping off the wheel under extreme off-road conditions, or when tire pressures have been lowered for rock crawling. 


Beater - is usually an off-road truck or Jeep that is dented and/or kind of  rough looking on the outside but runs like a stallion (mechanically sound).


Bed - usually refers to the bed or cargo area of a pick up truck. Different bed lengths are found on most make & model trucks.  For example, a 2006 Chevy Silverado 1500 comes in a 5'8" length bed, 6'6", and 8 ft.  Most commonly known as a short-bed or long-bed, with multiple lengths being offered today, it is easy to get confused.   
Bed Bar - A steel bar assembly (usually made from tubular bars) that can be bolted or welded to your truck bed. Typically, bed bars are more for style, and they don't offer the safety of a roll bar should your truck flip over off-roading. They are extremely useful for mounting off-road lights.


Beefed-Up or Beefing - is an off-road 4x4 that is stronger than stock. 2. An after-dinner condition on the trail.


Beltline - is the 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. 


Bench Race - is to talk about your truck and your driving feats as if they were fish stories.


Bezel - is a trim ring that is usually chromed or polished that surrounds headlights or gauges.


Bicycle Off-road - is a term used when you ride on either both right- or left-side of your vehicle’s wheels.


Bikini top - is a soft top that covers only the front seats and leaves the rear uncovered. Very popular on Jeeps and old Broncos.


Bell-housing - is a bell-shaped enclosure for the clutch and flywheel on a manual transmission.  On an automatic transmission, it is the flex-plate and torque converter.


Billet - is a part machined from a single piece of metal, not a casting.


Bleed - is to remove air in a hydraulic system by pumping out fluid. 


Blip - is a quick touch of the throttle to momentarily rev an engine.


Blower - another name for a supercharger or is sometimes what a ventilation system's motor is called.


Blown Engine - is a seriously damaged engine that usually will not start.  Also, a blown engine reference is when you have a supercharged engine.


Blow the Doors Off - is a term when you defeat a competitor during a speed contest in two or more vehicles.


Blueprint - is 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 - is the rear of the truck, SUV, of Jeep that has been shortened, usually adjusted for better departure angle or shorter wheelbase.


Body Armor - what Jeep and some truck owners call pieces of formed metal that is riveted or screwed into parts of the exterior body for extra protection or to cover up rust spots.


Body Roll - is a tendency of a truck's body and chassis to lean toward the outside of a turn as the result of cornering forces. 


Bog - means running an engine below its intended operating range by driving in too high of a gear for the speed or load. 


Bogger - is a vehicle built for mud racing or means simple one who mud-races. 


Boiling the Balonies - is a nickname for spinning your tires.


Bolt-on - is an aftermarket part or component that can be installed without special modifications or major disassembly.

Boneyard - another name for a wrecking yard, salvage yard, or junkyard.


Boost - is the increase in direct intake pressure above atmospheric pressure provided by a supercharger or turbocharger. Boost is measured in psi.


Bore - the inside diameter of a cylinder. Or, it can mean the act of machining a cylinder to fit larger pistons - “boring a cylinder”.


Bored-and-Stroked - is the combination of an enlarged cylinder bore and a lengthened piston stroke, resulting in an increase in engine displacement and power.


Bottom End - a collective name for the crankshaft, connecting rods, and main bearings of an engine.  Can also mean vehicle power at low engine speed.


Bottom-Out - it is when a truck's suspension is fully compressed and its bumpstops won't allow further suspension travel.


Boxed - to strengthen a frame by adding a metal plate to an open-channel frame-rail or crossmember, thereby turning a three-sided frame-rail 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.

Breakover Angle - Also known as "ramp break over angle.") The degree of slope that defines the largest ramp or hill that a vehicle can travel over without scraping its midsection between front and rear wheels against the ground. This is the maximum angle or degree of apex a vehicle can drive over with one forward wheel and one rear wheel touching the ground without getting high-centered (stuck) on an obstacle.

Bridle - is a form of winch strap or tow strap that's designed to be attached to two separate points such as the right and left chassis members of a vehicle. At its center where the straps meet, a bridle serves as a point of attachment for a tow rope, hook, etc. 


Broach - to pierce or open, sometimes referring to a splined cut on a flange or a gear.

Bull Bar - is an assembly that bolts to the front structure of a vehicle (usually frame and/or bumper) which is designed to protect the center and underside of the front bumper from damage caused by frontal and underside impacts. Bull bars serve to block crash energy from reaching softer front body panels, channeling it directly to the vehicle's structure. Bull bars usually include skid plates on their underside. 


Bullet-proof - Using the strongest components and upgrades for a truck or Jeep to make it super strong or indestructible 


Bump - to quickly touch the accelerator and immediately let off or to  back off another vehicle or obstacle, then hit it again with momentum.

Bumper Bar - is a tubular metal reinforcement assembly with two bars designed to offer full protection for a front or rear bumper area during minor parking speed impacts. Bumper bars mount to the steel frame of the vehicle rather than to the bumper itself, and offer minimal protection during off-roading.


Bump Steer - is a situation in which the steering jerks hard to the right or left when a truck or Jeep encounters a bad bump in the road. 


Bump Stick - another name for a camshaft on a vehicle.


Bump Stop - is the rubber or urethane block used to limit suspension compression travel.


Burnout - a deliberate spinning of the rear tires to heat and clean the tires' tread in preparation of maximum acceleration from a standing start.


Butt-Scratcher - a trail obstacle that scrapes on a truck or Jeeps rear end.





Cadence Braking - A method of manual braking with the foot brake to simulate the action of ABS brakes (see ABD definition above). Very effective in slippery conditions where brake locking has occurred or might otherwise occur, the driver applies the footbrake in a series of very rapid jabs at the pedal taking the wheels up to the point of brake locking and then releasing them before the inevitable fall-off in braking efficiency takes place. Effects improved braking in any extremely slippery conditions such as ice, snow, wet mud, or rain.


Cam - an eccentric device which converts rotating motion to reciprocating movement.  Cam is also used as an abbreviation to 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 - the amount of time, expressed in degrees of crankshaft rotation that a cam holds open the intake or exhaust valves.


Cam Lift -  the 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.


Capstan Winch - a winch, generally mounted on or just behind the front bumper, usually run from an engagable extension to the engine crankshaft. The active component is usually a slowly revolving drum, about 15 cm in diameter, round which a rope may be wound to effect a winching operation. A Capstan has the advantage of being powered by the engine at idling speed and being a very low-stress unit that may be used all day without overheating or high electrical load.


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 - or "CB Radio" stands for “citizens band radio” which is a two-way radio that is commonly used for communication between Jeeps & trucks off-road.  CB's became very popular in the 1970's and is still used by long-haul truck drivers to communicate as well as a lot of off-road trail riding clubs or groups. 


Center Disconnect - A four-wheel-drive system that engages the front axles at an inboard location rather than the outboard hubs.

Center of Gravity - A theoretical spot on a vehicle where all planes are balanced - from-left-to-right as well as front-to-rear. A vehicle's center of gravity (CoG) reflects how easily that vehicle will roll over. A high center of gravity makes a vehicle more top-heavy and more likely to tip over. For many off-road vehicles (especially lifted ones), the center of gravity is a foot or two above the ground and slightly forward from the center. Because this spot is higher than what's found on cars, 4x4s are more likely to tip over when off-roading


Cherry - is a vehicle that is clean and in unusually great shape.


CFM - stands for 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.


Chain Drive - a system in which a chain and sprockets drive gears instead of the gears being meshed together.


Chicken-Handle - a handle for passengers to grab when the going gets rough


Chip - a simple nick in the paint of a vehicle caused by road debris like rocks.


Chirp the Tires - to shift quickly during hard acceleration so that the tires momentarily lose traction.

Chunk - slang word for the ring-and-pinion gear assembly inside a differential housing. Or, chunk can mean when a vehicle part ejects from their original or functional location.


Clip - a truck's entire front sheet metal 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 multi-link suspensions because they offer the advantages of easy preload and ride-height adjustments, lots of wheel travel, and accurate spring damping rates.


Collector - device that collects exhaust gases from the exhaust manifold (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 - the part of a tire tread that is in contact with the road surface when the tire is turning.


Coordinated Tow - the process, when recovering a truck or Jeep, when the engine power of both the tow or tug and the stuck vehicle are coordinated and the clutches of both vehicles are engaged at the same time to enhance the chance of getting unstuck.


Cornbinder - slang for any 4x4 made by InternationalHarvester because the company is known for making farm equipment. Syn. 'Binder.


Crank It - to turn the steering wheel hard to the left or right while driving or it can simply mean to start the engine.


Crankshaft - the shaft with a large, U-shaped crank that is connected to the pistons' connecting rods and transforms the pistons' reciprocal motion to a rotational motion, which powers the drivetrain. 


Crawl Ratio - sometimes called the “granny gear” is the ratio of torque at the wheel to the torque at the engine’s flywheel. It is how many times the engine torque is multiplied before the actual propulsion occurs and is factored by three components: the transmission, the transfer case, and the differential. That number also shows how many times the final driveshaft will rotate per rotation of the engine’s crankshaft. Vehicles with high crawl ratios are better for a variety of situations like pulling large loads, climbing steep inclines, and driving over large obstacles, although they’ll travel very slowly in the crawl ratio.


Cross-Drilled Crank - a crankshaft with additional lubrication holes drilled opposite the existing main journal oil feed holes, providing improved high-rpm-bearing lubrication.


Curb Weight - is the 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 - is a constant velocity joint, two U-joints in tandem or a Rzeppa joint allows for increased angularity of driveline components. Commonly found on front driveshafts and front-drive axles.


Cylinder Head - is the part of an engine that contains the valve-train and the combustion chambers and covers the tops of the cylinders and pistons.



Deck - the surface of the engine block on which the head gasket and cylinder sit.


Degreeing a Cam - Using a dial indicator and a degree wheel to verify that a cam's lift and duration is accurate.


Departure Angle - Like approach angle, this is the maximum angle of clearance on a vehicle when exiting an obstacle or descending a hill. It is defined as the angle between the ground and the line drawn between the rear tire and the lowest-hanging part of a vehicle (often the bumper).


Detroit Locker - A popular brand of automatic locking differential.


Dial-In - to set up a truck's engine, chassis, drivetrain, stereo, or other system so that maximum performance results. Or, a

dial-in is to set up a mechanical component for trouble-free operation.


Differential Type - Differentials help improve traction by preventing excess wheel spin. They go by a variety of names like locking differential, differential lock, diff lock, or locker. Differentials come in five main types: open, selectable, automatic, limited slip, and spool.


Open Differential - the most common in standard cars and does not restrict how much more one wheel can spin than the other.  However, off-road vehicles usually have one of the following differentials:


 - Selectable Differential - activated by a button or a switch inside the vehicle, a selectable differential is also known as an E-Locker. This is one of the more preferred differential options because it allows the driver manual control over the lockers without having to get out of the vehicle. 

 - Automatic Differential - an automatic locks down the axle when it senses slippage and lets go under normal use, like highway or normal driving. It is beneficial, especially to off-road drivers, who don’t want to deal with remembering to engage the differential. The one consistent complaint of an automatic differential is engaging when the driver prefers it not to.  

 - Limited-Slip Differential - the limited-slip simply limits the slip between the wheels, but does not fully lock them. This option is popular in mild to medium off-road driving since the differential  engages automatically and it isn’t a fully engaged locker. Limited-Slip allows the driver to turn effectively as if not engaged at all.  The negative is it isn’t a true locker and can’t fully engage to lock the axle; some slip is still possible so very challenging terrain is not recommended.

 - Spool Differential - is a very simple, one-piece unit that keeps the axle always locked. It is useful for vehicles meant to go in a straight line, like serious drag cars.  Spools are not a realistic option for 95% of most off-road vehicles that need to maneuver on trails.


Direct Ignition System - an ignition system that has no distributor; ignition is sent directly from the multiple modulators (coils to the spark plugs).


Directional Tire - a tire with an asymmetrical tread that is designed to produce superior off-road traction when rotating in one direction only.


Double-Line - a type of winch rigging that runs the cable to an anchor point and back to the vehicle, thereby doubling the pulling power.


Double-pumper - a four-barrel carburetor with mechanical linkage to open both the primary and secondary barrels and mechanical accelerator pumps in both the primary and secondery.


Drag Link - is a steering link that connects the pitman arm to the steering arm.


D-Ring - A heavy-duty, D-shaped steel hook used at the end of tow straps, chains, or cables used for pulling or winching a vehicle out of trouble.


D-Ring Attachment - A metal eyehole plate that's bolted or welded in place in order to serve as an anchor point for heavy-duty metal D-rings or other hooks. D-ring attachments can be found on some bumpers, grille guards, bull bars, and other similar reinforcements


Drive Type - This option indicates to which wheels power is transferred from the engine. Possible values include:

  • FWD - Front wheel drive. With this drive type, power is transferred to the front wheels.

  • RWD - Rear wheel drive. With this drive type, power is transferred to the rear wheels.

  • 4WD - Four-wheel drive. With this drive type, power is transferred to the rear wheels but can be "turned on" to the front wheels as well.

  • 2WD - Two-wheel drive. With this type in the off-road arena means a truck that only has rear two-wheel drive capabilities.

  • AWD - All-wheel drive. With this drive type, power is transferred to all wheels at all times.


Droop - a name for any downward suspension travel.


Drop the Hammer - to accelerate rapidly from a stop.


Dropped Pitman Arm - an offset arm that lessens the angle between the steering box and drag link.


Drum Storage Capacity (Winching) - The maximum length of cable or wire rope that can be wound around a drum without exceeding the maximum number of layers. It can vary depending on the thickness and diameter of the cable and is usually expressed in feet or meters. Sometimes called “cable capacity on the spool”


Dualie - a truck that has dual rear tires on each side that is mainly used for hauling heavier gooseneck trailers.


Dual Plane - An intake manifold with runners that do not share a common plenum, usually designed for low - to midrange engine performance.


Duty Cycle - The operating cycle of a machine or other electrical device that operates intermittently rather than continuously. "Duty cycle" is a number representing "ON" time as a percentage of one complete on-off cycle. The total length of the cycle is irrelevant. For example, a 25% Duty Cycle as illustrated above means the device is "ON" for 25% of the time, and "OFF" for 75% of the time. If the complete on-off cycle is 1 minute (60 seconds), the "ON" time is 15 seconds (60 x .25), and the "OFF" time is 45 seconds (60 x .75). Winches have duty cycles in order to avoid overheating.


Duty Cycle Thermal Rating - On a winch, the distance a specified load can be hoisted and lowered before the lubricating oil rises from 100°F to a 250°F (or other) maximum gear oil temperature. 


Dyno - Abbreviation for dynamometer, a machine used to measure engine torque either at the flywheel (engine dyno) or rear tires (chassis dyno).

D Glossary


EAS - electronic air suspension. Introduced in the 1993 model year on certain Range Rover models further to enhance standards of road noise insulation, ride and handling, the system substitutes air bags and a live-line pneumatic system, (ie an electrically driven compressor, air pressure reservoir and associated controls) for the steel coil springs used on the rest of the Land Rover model range. Logic- controlled by an electronic control unit, height sensors and driver controls, the system maintains front and rear self-levelling in the five height modes listed below. These notes show the versatility of the system and the purpose for which it was designed. However, for the casual driver, new to the vehicle, no prior knowledge or expertise is required; FAS will cycle automatically through appropriate modes according to prior programming. The driver need not even know EAS is fitted. On engine start-up EAS assumes the last selected ride height.


ECU - Electronic Control Unit, computer unit for engine management.


ETC (Electronic traction control) - is a standard/optional feature, available only on ABS-equipped Range Rovers. It inhibits wheel-spin by applying brake to a spinning rear wheel and thus enhances traction on ice, snow or in severe off-road conditions. It utilises ABS sensors for wheel speed determination and brakes the spinning wheel to, through the axle differential, apply torque to the stationary wheel. Like ABS. it is especially effective in maintaining control when one side of the vehicle is on a more slippery surface than the other - a so-called 'split-p surface. A dashboard light illuminates when the system is operating. The function is inhibited above 50 kph, a speed above which unintentional wheel spin is unlikely to occur.


EFI - Electronic Fuel Injection; computer-controlled fuel delivery system.


EGR - Exhaust Gas Recirculation, an emissions-controlled device that reintroduces burned exhaust gases to an engine's combustion chamber.


Electronic Ignition - Ignition system that uses transistorized circuits instead of breaker points.


E.O. Number - Executive Order Number, the number assigned to a part by the California Air Resources Board when it becomes legal to use on emissions-controlled vehicles.


Exhaust Back-Pressure - Resistance to the free flow of exhaust gases through an exhaust system


Exhaust Headers - Performance exhaust manifold built from equal-length steel tubes that is designed to speed the flow of exhaust gases exiting the cylinder head(s).


Exhaust Manifold - Tubular cast-iron component that routes exhaust gases from the cylinders to the exhaust system.


Fairlead - A steel guide installed onto a winch mount to help direct the winch cable. A Hawse type fairlead (shown on the left) features a simple bracket with curved edges for the cable to slide against, and a roller type fairlead (shown on right) uses moving rollers on all four sides to reduce friction. Fairleads come in two styles: roller, which uses steel rollers, or Hawse, which features a simple bracket with large radiused edges for the cable to ride against.


Fan Clutch - Thermostatically controlled clutch device that engages or disengages a mechanical radiator cooling fan according to the engine's cooling needs.


Flathead - An early engine design that located the valves in the block beside the cylinders, rather than the head (overhead valves) as is currently done.


Flat Spot - Momentary decrease in engine power at some point within the powerband.


Flat-Top - a piston without a dish or a dome. 2. A popular '50s haircut.


FlexBilt - a popular brand in the Southeast that customizes Jeeps, trucks, and SUV’s for optimal off-road performance.  


Flex - another name for axle articulation which is the off-road vehicle's wheel and axle travel while keeping all four tires in contact with the terrain.  The more greater the “Flex” usually indicates a Jeep or truck's off-road abilities.    


Forced Induction - describes a supercharged or turbocharged vehicle.


Four-Banger - a slang term for a four-cylinder engine.


Four-Bolt Main - A crankshaft's main bearing caps held in place by four bolts.


Free-wheeling - When the front hubs are unlocked and the wheels spin because of momentum rather than power.


Fuelie - Old slang referring to a fuel-injected engine or vehicle.


Fuel Injector -  Electromechanical device that squirts fuel into an engine.


Full-Floater - An axle assembly designed to hold the weight of the vehicle on the axle housing instead of on the axle shafts; has bearings at both the differential and wheel ends.


Gas Shock - Damper shock absorber with two separate compartments, one containing hydraulic fluid, one containing nitrogen gas. The gas keeps pressure on a flexible, in some cases, moveable separating disc, that, in turn, keeps pressure on the fluid, thereby reducing the fluid's tendency to foam during aggressive driving.


G-force - Measurement of the force generated during cornering, acceleration, or deceleration, expressed in units of gravity.


Glasspacks - Tubular style of muffler that uses fiberglass packing to absorb sound.


Gnarly - A difficult portion of a trail that may or may not make you nervous. Syn. exceptional.


Go-Juice - another name for gasoline


Granny Gear - An extremely low First gear in a manual transmission. For example, an SM465 has a 6.55:1 First gear ratio.


Grenade - Catastrophic failure of an expensive part. Engines, transmissions, and axle assemblies can all grenade.


Greenhouse - Upper portion of a truck's body; the structure above the beltline, including the roof, windows, and pillars. Syn. office.


Ground Effect - Reduced airflow under a truck provided by an air dam and side skirts. Less pressure underneath a truck allows the air passing over its top to push downward, thus creating an improved grip on the road as well as improved top speed and fuel efficiency. Impedes ground clearance in 4x4s.


Gumbo - Deep, sticky mud.


Gun it - To deliberately rev an engine.


Gusset - Triangular metal support used to add strength; is welded in place where two frame rails connect or where two tubes of a roll cage are welded together.


GVWR - Gross Vehicle Weight Rating, the combined weight of a vehicle and its rated cargo capacity.

Grille Guard - An assembly that bolts to the front structure around the bumper of a vehicle designed to protect the center area of the front bumper and grille from damage caused by straight-on frontal impacts. Grille guards serve to block crash energy from reaching softer front body panels, channeling it directly to the vehicle's structure. 


Ground Clearance - is often looked at as an easy solution but just "lifting" your off-road vehicle.  Ground clearance is a very important i-factor when off-roading and is not just the ride height of an off-road vehicle.  It is defined as the amount of space between the lowest part of the vehicle and the ground. Vehicles with higher ground clearance are less likely to get hung up on obstacles like tree trunks, boulders, and even small to medium sized rocks while on and off the trails. Lifting a vehicle can improve ground clearance, as can fitting larger tires. Depending on the vehicle, that lowest part may be an axle differential, part of the exhaust system, or other component. The off-road vehicles with the best ground clearance are usually the ones with a professionally installed suspension lift kit. 

G glossary
F glossary
E glossary



Halogen Light - High-output headlight or driving light that has halogen gas inside the bulb. When surrounded by a halogen gas, the bulb's tungsten filament can carry a higher current, thus producing a more brilliant white light.


Hammered - 1. A truck that's thoroughly destroyed. 2. A truck that has a chopped top or a severely lowered suspension.


Handle - The nickname you use on the CB.


H.E.I. - High-Energy Ignition, a powerful and reliable GM distributor assembly with a self-contained coil.


Heliarc - Perfected by Russell Meredith in 1941, Heliarc, also known as Gas Tungsten Arc Welding (GTAW) or more popular TIG (Tungsten Inert Gas) welding is one of the more popular welding techniques. The TIG welding process is to make an arc in between the base metal and the tungsten electrode (the non-consumable). A weld pool will form upon which the welder will begin to hand feed a filler metal.


Helicoil - Stripped thread repair system, consisting of small coil-spring inserts that thread into place on damaged female screw threads.


High Centered - When a vehicle is stuck because its midsection between the front and rear axle has become lodged over obstacles or ground, with front and rear wheels too far off the ground to achieve sufficient breakaway grip. 


High-pinion - See reverse-rotation.


Hi-Po - slang for High-performance.


Hole Shot - Beating a competitor at the start of a race; coming off of a dead stop quicker; coming out of the hole quicker.


Hook Up - a term usually used off-road simply means to gain traction.


Hub - Wheel mounting surface on a vehicle.


Huffer - A belt driven supercharger.


Hydraulic'd - What it’s said when an engine has been submerged in water and has sucked water into its cylinders through the intake and will no longer rotate because the pistons moving up the cylinders cannot compress the water.





IFS - acronym for Independent Front Suspension, a type of suspension system that allows the two tires on one axle housing to move separately from one another.
Intake ports -  Passages within a cylinder head that route air and fuel to the intake valves.



Juicebox - a nickname for automatic transmissions.


Kick-Down -  Quick downshift on an automatic transmission when the engine is given full throttle.

Kicker Shocks - Shocks mounted in a near horizontal position between the axle housing and the leaf springs. Kicker shocks are valved with a high rate of compression damping and are intended to reduce axle wrap.

Kick-Up - Section of a frame that is curved up to clear an axle housing.


Ladder Bars - Longitudinal suspension control arms that connect the axle to the frame, preventing axle wind-up and hop.

Lash - the amount of clearance between a valve and a rocker arm or between a rocker arm and a lifter or pushrod.

Lateral Link - Tubular suspension rod that positions the axle housing so that side-to-side movement is minimized during cornering.

LED - acronym for “Light-Emitting Diode” - LED is a small semiconductor that lights up when current is passed through it. LED is now one of the most popular off-road lighting options through light bars, light pods, grill and rack lighting, taillights, and much more. 

Leveling Kit - is a hardware kit to raise the front of a truck (usually a truck) ever so slightly so it matches the stock height in the back. A leveling kit is usually designed to provide a maximum lift of about 2 inches in the front. If a stock-style stance is desired, front-end leveling kits can be paired with spacer blocks on the rear leaf springs to provide a slight lift at all four corners. Leveling kits are also very simple and usually only require spring spacers or torsion keys to provide an equal lift from front to back of a pickup truck.

Lift-Block - A spacer placed between the axle assembly and the springs to lift a truck inexpensively. These are only safe on rear-axle assemblies.

Lift Kit or Lift - Whether it is a suspension lift kit or a more simpler body lift kit, lifting a vehicle is typically done through a custom fit kit which changes out various suspension parts and/or puts blocks near the wheels to raise the vehicle upward. This can be done to improve ground clearance or simply to achieve a more dominant look.  Solid-axle pickups and body-on-frame SUVs are lifted since they have solid steel components to work with. Unibody SUVs and vehicles with independent front suspension can be lifted, yet it requires much more work to achieve the same results with their extra parts and complexity.

Lift-Block - or “spacer block” is just another name other than Lift-Block.  A lift-block is just a spacer placed between a rear axle assembly and springs to provide an inexpensive ride height lift or boost that's suitable for off-roading. 

Limited-slip Differential - Final-drive system where left and right axle shafts are mechanically connected via a series of pinion gears to prevent wheel spin on slippery surfaces and to ensure that the engine's power is transmitted equally on both sides of the vehicle. 

Line - Sometimes called “drive-line” or “trail-line”, is an off-road driver's selected path that provides the best route for a 4x4 to climb over an obstacle or through a challenging path, up a mountain, or through a rock climb.  The “right line” is essential to successful four-wheeling to minimize stress on axles, wheels & tires, and suspension.

Light it Off - slang for starting an engine.
limited-slip Differential - Final-drive system where the two axle shafts are mechanically connected with a series of clutchlike plates to prevent wheelspin on slippery surfaces and to ensure that the engine's power is transmitted equally between the two tires.


Line - A driver-selected path that gives a truck the best route to climb over an obstacle or through a pathway. Choosing the right line is essential to successful four-wheeling.

Locked In - To have engaged the manual front hubs into the lock position.

Locker - A device in either the front or rear differential that sends engine power to both wheels regardless of traction.

Lockers Front and Rear - One of the most common truck-owner fibs.

Loctite - A product used on fasteners to maintain torque.

Long-Block - is an engine assembly consisting of a cylinder block, a crankshaft, a camshaft, bearings, pistons and rings, connecting

rods, an oil pump, an oil pan, a timing cover, seals, cylinder heads, and an intake manifold.

Loud Pedal -  slang for “Accelerator”

Low Gears - gears that increase the amount of reduction in the transmission, transfer case, or axle. In an axle, they are expressed as the ratio of ring-gear teeth to pinion teeth, so low gears are numerically higher than high gears. (Example: 4.10 gears are lower than 3.55 gears.) Rockcrawler Jeep and off-road lifted trucks typically have low gears.

Low-Lock - To have the transfer case in 4-Lo therefore locking out the center differential, if so equipped.

Locked-In - When manually adjustable front axle hubs are moved from freewheeling 2-wheel-drive and locked into position in 4-wheel-drive mode.

Locker - A device in either the front or rear differential that sends engine power to both wheels regardless of traction.

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Mandrel Bend -  is a hydraulic or mechanical tube-bending machine that uses dies and mandrels (forms) to bend tubing in such a manner that the walls don't collapse.
Manifold Cooking - To use a hot intake manifold as a heat source for cooking on the trail. It is known that cans of beans, burritos, and other “trail delicacies” are favorite manifold cuisine.
MAF - stands for “Mass Air Flow” - MAF sensor is one of the key components of an electronic fuel injection system in your off-road vehicle. The MAF sensor is usually between the intake manifold and the air filter and measures the amount of airflow into the intake manifold. The data the sensor collects, along with other data/sensors, is collected and sent to the engine's computer, which calibrates the optimum air. 
Meats - slang for extra-large off-road tires. Synonyms: skins or shoes.
MIG Welding - stands for “Metal Inert Gas”. It is a welding technique that is a wire-fed welding system that uses argon gas as a shielding agent for the weld. Steel, stainless steel, aluminum, and other metals are commonly welded with a MIG welder.
Mill - another short name for “engine” or a “milling machine”.
Modular Wheel - Custom or racing wheel with an inner, an outer, and a center section that are bolted or riveted together.
Monochrome - Styling inspired by European performance cars where the bumpers, grille, body trim, and door handles are painted the same color as the body.
Mountain Motor
- Big-block engine, typically bored and stroked to at least 500 cubic inches.
Mouse Motor - Chevy small-block V-8 engine, named Mouse because of its small overall physical size, and because, some say, GM executives wanted to scare Chrysler's "elephant" Hemi engine with the new, powerful small-block Chevy.
Multilink Solid-Axle - suspension design where coil springs are used instead of leaf springs, and the axle is located by longitudinal and lateral suspension control arms, or links.
Nail It - To apply full throttle.
Negative offset - When the wheel's mounting surface is outboard of its centerline.
Normally Aspirated - An engine that relies on vacuum through its intake manifold and cylinders to draw in an air-fuel mixture; an engine without a forced-induction supercharger or turbocharger.
NOS - 1. New old stock; original equipment, unused parts for vintage trucks, often found in their factory cartons at dealerships. Ant. repro, reproduction. 2. A nitrous oxide injection company. 3. Slang for nitrous.




OEM - Original equipment manufacturer. Syn. stock.


Oil Sending Unit - also called an oil pressure switch or sensor, controls the oil indicator light or gauge inside the cab of the vehicle. The indicator tells the driver of any problems with the oil pressure. For example, low oil pressure while taking on off-road challenges can lead to engine damage and/or over-heating.  You can test the sending unit if you believe it isn't accurate by buying or renting an oil pressure testing gauge at most auto parts stores.

Off-Camber - A situation in which the truck is sideways on an incline, increasing the likelihood of a rollover.


OHV - stand for "Off-Highway Vehicle", is a designation by the vehicle's manufacturer that its primarily use if for unimproved terrain and weighs less than 2,500 pounds.  Most states that have a lot of off-road trails require a valid OHV decal to operate on public and state trust lands.  Both residents and non-residents are required to purchase an OHV decal for each vehicle. 

Oil Gallery - Small passages within the engine block and cylinder heads through which lubricating oil circulates.


One-Off - 1. Custom part or component that is fabricated from plans; no other identical copy exists. 2. Wide-production modifications to an existing vehicle, such as a Saleen Explorer.


Out to Lunch - Worthless, a truck that doesn't run well or look right.


Oversteer - Cornering condition where the rear tires slide toward the outside of the turn.

Off-Camber - A situation where a vehicle is sideways enough on an incline to increase chances of a rollover.

Off-Road Bumper - A front or rear replacement bumper (typically made from heavy gauge steel) that features angled corners and edges that provide extra ground clearance. Where OEM bumpers would normally scrape the ground during steep departure and approach angles off-roading, off-roading bumpers will not.


Panhard Rod - A transverse link (rod that attaches to the truck's frame at one end and to the axle housing at the opposite end), providing lateral positioning of the axle housing relative to the chassis.

Paper-weight - A part that's broken beyond repair can be used as an excellent paperweight.

Payload - Maximum weight a truck can carry, calculated by subtracting the curb weight of the truck and a 150-pound allowance for each passenger from the gross vehicle weight rating.

Peg-Leg - An open differential. Syn. one-legger.

Pickle Fork - Fork-like tool used to separate suspension components, such as ball joints and tie-rod ends, for repair.

Pinion Angle - The angle of the pinion yoke on an axlehousing in relation to its driveshaft.

Pitman Arm - Steering lever that converts the rotary motion of the steering box to the linear motion of the steering system's centerlink.

Plenum - Box or cavity at the intake manifold's entrance that stores the air/fuel mix for distribution to the intake runners.

Plow - Understeer.

Port Injection - Electronic fuel-injection system that injects fuel directly into the cylinder-head ports.

Posi - Short for Posi-traction, a limited-slip differential used by General Motors. The term is often used generically for any limited-slip device.

Positive Offset - When the wheel's mounting surface is inboard of its centerline.

Prerunner - An off-road truck that's built to pre-run a desert race course so that the driver can study and practice on the course before the race.

Pro-Charger - is an engine which has both a supercharger and a turbocharger for forced induction systems.

Progressive-Rate Springs - Suspension springs that become progressively stiffer as they are compressed.

Proportioning Valve - Hydraulic braking valve that varies the braking force at the front or rear wheels, depending on pedal pressure, load, and weight transfer, to reduce or eliminate wheel lockup.

P.T.O. - Power take-off, an accessory powered by engine output, usually a winch.

Pumpkin - The center section of an axle housing that contains the differential carrier and gear set. Syn. coconut, third member.

Push-Rod - Thin metal rods that transmit the motion from the camshaft and lifters to the rocker arms, and thus operate the valves on an overhead-valve (OHV) engine.

Push bar(s) - A metal bar(s) that's an extension to a grille guard or add-on to an off-road bumper designed to align with the bumper of another vehicle. Push bars allow you to use your vehicle to gently push another without causing damage because pressure is evenly applied. Horizontal push bars are often referred to as "pre-runner" bars.

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Quad - has two definitions; either a four-barrel carburetor or a four-wheeled all-terrain vehicle (ATV).


Quarter-Panel - is a body shop term for the front or rear corner sheet metal assembly of a vehicle’s body.

Radius Arms - Brackets used by Ford that locate the front axle housing on coil-spring suspensions. Dodge and Jeep use similar brackets. Syn. trailing or control arms.


Rack-and-Pinion - A steering system that uses a pinion gear at the end of the steering shaft to engage a horizontal-toothed bar, the rack, which is attached to the tie rods and the steering knuckles.


Rake - When the frontend of a truck sits lower than the rear.


Ramp Breakover Angle - The angle formed by lines drawn from the front and rear tires' contact patches and the midpoint of the wheelbase on the chassis; the greater the angle, the less likelihood of high-centering.


Ramp Travel Index or RTI - is an index that shows how high an off-road (usually a Jeep) can climb up an object with just one tire while the other three tires remain on the ground.  There is a competition that uses a 20 degree one-wheel ramp that is scored with all four tires maintaining contact, by measuring the distance traveled up the RTI ramp at the center of the wheel and dividing the vehicle’s actual wheelbase, and then multiplying by 1000.  With all of the varying wheelbases, this calculation allows all trucks & Jeeps with varying suspensions to compete on the same ramp while keeping it fair.  


Rat - Chevy big-block V-8 engines, normally offered in 396ci, 402ci, 427ci, and 454ci sizes. Named because it was a large companion to Chevrolet's small-block Mouse V-8.


Rebound - After a suspension spring is compressed by a bump, the spring naturally tries to return to its previous length, extending the suspension upward toward its original ride height.


Recirculating Ball Steering - Steering assembly that uses a worm gear on the end of the steering shaft to turn a sector gear that is within the steering box and attached to the pitman arm. Ball bearings are used between the worm and sector gears for smooth operation.


Redline - Absolute maximum engine speed, expressed in rpm, at which an engine can/should be operated; indicated by a red line on the tachometer. Syn. rev limit.


Repro - Aftermarket reproduction parts, manufactured to appear, fit, and function as originals. Not the same as OE or N.O.S., which are both factory-issued parts.


Restify - To build a truck that is basically restored but has been updated with modern convenience and performance enhancements.


Retrofit - Installing new parts or systems on an older truck for the purpose of upgrading, such as retrofitting a modern fuel-injection system in place of the original carburetor.


Rev Limiter - An adjustable electronic device that restricts engine rpm to a predetermined limit so engine damage does not occur.


Reverse-Rotation - Refers to an axle design where the pinion is positioned above the axle centerline.


Ring-and-Pinion - a Gear Set that drives the wheels; the pinion is a gear attached to the rear of the driveshaft, and the ring gear is part of the differential that turns the axles.


Rock Magnet - A low-hanging component of a 4x4, such as a ladder bar, that seems to catch on every obstacle.


Rock Massaging - Body damage caused by rocks and other obstacles on the trail.


Rocker Arm - Pivoting valvetrain levers. One end of an engine's rocker arms are moved by the pushrods/lifters and the opposite end's

open intake or exhaust valves.

Rocker Bars - Also known as "rocker guards", these bolt to the frame along the sides of your vehicle and serve to protect vulnerable rocker panel body pieces that can get damaged during off-roading.


Rocker Panel - The sheet metal section of a truck's body located below the doors and between the front and rear wheel openings.


Roots Supercharger - Positive-displacement, belt driven supercharger; originally designed in 1859 by Francis Roots for use as a water pump.


RTI - Ramp travel index, a measurement of suspension flexibility and articulation that's calculated by dividing the distance the hub's centerline travels up a (usually 20-degree) ramp by the vehicle's wheelbase in inches, multiplied by 1,000.




Sand Ladders - A form of traction aid consisting of a pair of ramps with perforations designed to increase tire grip. These ladders are placed beneath the wheels of a vehicle that has become stuck in muck or snow to provide a firm traction surface that would not otherwise exist.


Sanitary - Well designed, engineered, and constructed; cleanly built; superior mechanical workmanship. Syn. sano.


Semi-Floater - An axle assembly that carries the weight of the vehicle on the axle shafts. These are typically weaker than full-floaters.


Serpentine Belt - Engine accessory drive belt that is long and follows a snaking path while driving the alternator, water pump, A/C unit, and power-steering pulleys.


Shackle - Connector between the rear of a leaf-spring pack and the frame; allows the spring to lengthen as the suspension is compressed.


Shift Kit - Package of high-performance components for an automatic transmission that firms the shifts, alters the shift points, and improves overall performance.


Shiny-Side Down - When a truck rolls over. Syn. rubber-side up.


Short-Block - An engine block that has a complete bottom end, including the crankshaft, rods, pistons, and camshaft, but without the cylinder heads, intake and exhaust manifolds, water pump, and other accessories.


Sidehill - A portion of a trail that leads across a steep hill instead of up or down. See off-camber.


Single-Plane Manifold - Intake manifold with a single plenum feeding all of the engine's intake runners.


Skin - Body sheet metal.


Skins - Just another slang word for “tires”.


Slickrock - A type of sandstone dominant in Moab, Utah. Slickrock actually isn't slick and provides excellent traction.


Slushbox - An automatic transmission. Syn. juicebox.


Small-Block - A V-8 engine typically having 400 or less cubic inches of displacement.


Snatch-Block - A pulley device used in assisting with getting unstuck; it doubles as a winch cable's pulling power.


Snatch Strap - A thick nylon strap used to pull out stuck vehicles. Syn. tow strap, yank strap.


Spool Out - To pull the winch cable off the drum after releasing the brake.


Spotter - A co-driver who helps guide the driver over obstacles, often using hand signals.


Spring Rate - The force required to deflect a spring 1 inch, expressed in pounds per inch of spring compression or deflection. The higher the per-inch spring rate, the stiffer the spring.


Spun Bearing - A bearing that is either worn or frozen and has rotated in its retainer. In an engine, this causes the bearing to block off its oil passage and results in major damage.


Stair-Step - An obstacle that contains one or more ledges that must be climbed in succession. Stair steps are common on trails that follow washes or creek beds.


Stand on it - Full-throttle acceleration.


Swamped - To drown the engine; to drown the entire truck.


Synthetic Oil - Manmade lubricants; they generally have a greater capacity to lubricate and resist heat than standard mineral oil.  Also, called “Synthoil” (Liqui-Moly)

Skid Plate - A flat metal plate that bolts onto the frame of your car, grille guard, bull bar, or bumper. Offers protection for mechanicals behind it such as oil pans, differential, steering linkages, etc. that are particularly vulnerable when off-roading over uneven terrain.
Snatch-block - Pulley device that can be used in conjunction with a winch to vary the angle of pulling when necessary. Used properly, it can even double a winch cable's pulling power.


Spool out - To allow the winch cable to unwind off the drum after releasing the winch's drum brake.

Spring Rate - Linear vs. Dual vs Progressive - As a pound-per-square-inch measurement, it's the force required to compress a coil spring 1 inch. The higher the per-inch spring rate, the stiffer the spring. Spring rate is also used to describe whether a spring has the same rate of compression at all points during its travel ("linear"), gets progressively stiffer the more it compresses ("progressive"), or be specially configured to change characteristics abruptly ("dual rate.)

Spring Type -  This option refers to the type of suspension in the front and rear of the vehicle. For example, the 2010 Chevrolet Silverado 1500 has coil springs in the front and leaf springs in the rear. Possible spring types include coil, leaf, torsion bar, air, rubber, torsion, and hydraulic.  You will find coil springs and leaf springs on most heavy-duty trucks, Jeeps, and SUV's

Stair-step - In off-roading, a series of one or more ledges that must be climbed in succession. Stair steps are common on trails that follow creek beds.

Stinger Bar - A front-mounted assembly that's an extension to a grille guard, or an add-on to an off-road bumper. Stinger bars are angled upward at a steep rake to prevent your vehicle from tumbling off its wheels onto the front end should an end-over-end tumble become imminent down a steep descent. Stinger bars are also helpful in allowing you to slide out of a hole without burying your front end.

Suspension - When off-roading, the type of suspension you have can make a big difference in how well your vehicle can tackle obstacles – and in ride comfort. There are three main types of suspensions used for off-roaders: solid axle, four-link, and independent front suspension. 

Solid axle suspension typically uses either leaf springs or coil springs to handle various loads applied to it, with solid axles delivering power to the wheels. It is generally thought to be the best suspension for modification and for serious off-road oriented vehicles. 
Four-link suspension uses four “links” – metal bars – to handle the ride load and articulation of the vehicle. Essentially, two top links connect the frame to the top center of the rear axle, while two lower links connect to outer ends of the axle tubes (axle shafts). These four links work in harmony to handle the various loads placed on the vehicle, including side-to-side loads, to provide a smooth ride quality.
Independent front suspension uses control arms to handle the loads and road vibrations instead of a solid axle. It can be found on a variety of off-road vehicles and all GMC and Chevy trucks and SUVs, including heavy-duty models. Generally, it is considered IFS vehicles have a better ride quality than a solid axle vehicle, yet they sacrifice wheel articulation.


Suspension Travel - The amount of vertical wheel travel permitted by an off-road Jeep or truck suspension. The greater the suspension travel, the more valuable asset becomes on uneven ground and/or rocky terrain.


Sway BarSway bars on your vehicle are critical since they assist in helping manage your vehicle’s body roll by connecting the movement of what are otherwise two independent wheel assemblies. The sway bar link is what connects the sway bar to the other suspension component, which is typically the control arm. As one side of a vehicle rolls as it corners, one side of the suspension will compress more than the other. The sway bar’s job is to offer more resistance to the inside tire while also compressing the other side so that the vehicle has less body roll. This will even out the weight distribution of the vehicle, which improves handling in a corner. The sway bar links also smoothen the motion transfer between the control arm and the sway bar.

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Tachometer - Device used to measure and display engine speed, expressed in revolutions per minute. Syn. tach.
Tack Welds - Series of small welds, spaced approximately 1 inch apart, which are used to hold together two pieces of metal until the final welding can be performed.
Taco'd - a slang term when your axle housings, frames, or other components that have been severely bent, usually from jumping the truck.
Tail Gunner - The last vehicle/driver on a trail ride. The tail gunner is responsible for making sure everyone completes the trail.
Tall Gears - The opposite of low gears, they are represented in ratios that are numerically lower than "low" gears; e.g., 3.08s are taller than 4.10s.
TBI - acronym for “throttle-body fuel injection”.
T-case - Another name for transfer case.
Threshold Braking - Applying as much pressure to the brake pedal as possible without going to wheel lockup.
Throwout Bearing - On a clutch assembly, a shaft-mounted bearing that is moved from pressure on the clutch pedal and disengages the clutch disc from the engine.
Tie Rod - Steering linkage between the pitman or idler arm and a steering arm that moves the steering knuckles.
TIG Welding - Tungsten Inert Gas welding, also referred to as heliarc welding, usually used for joining aluminum and stainless steel.
Timing Chain/Gears - Chain or gears that transmit rotation from the crankshaft to the camshaft.


Tire Type - Tires come in a variety of different types, including passenger, truck, all-terrain, and mud/snow. Each of these tires is for a specific purpose and will perform differently. Most heavy-duty trucks have truck tires, which are distinguished by load range. SUVs and consumer pickups often have all-terrain tires with tread meant to handle a variety of elements like rain, sleet, highway, and moderate off-road terrain. Mud/snow tires are often found on serious off-road vehicles and can have large pieces of rubber sticking out for better traction. These tires offer a trade-off between traction and ride comfort; their knobbly design is also loud on pavement especially when a truck or Jeep has this type of tire going over 35 mph.
Toe-in, Toe-out - Inclination of a pair of front wheels slightly inward or outward as viewed from the truck's front.
Torque Converter - Fluid coupling between the engine and the automatic transmission. The engine powers a fan-shaped impeller inside the torque converter, which splashes oil onto a turbine (another fan-shaped device), and the turbine transmits its power to the transmission's gearbox.
Torsion Bar - Suspension spring that looks like a long metal rod. One end is attached to the truck's frame, and the other end is attached to the suspension's A-arm. When the A-arm moves, the torsion bar is twisted and then springs back to its original shape, thus its springing action.


Tow Hooks - These are metal hooks attached to either the front or rear of a vehicle and generally anchored to the frame. Better tow hooks extend beyond the bumper to make hooking them up with a tow strap or chain easier than crawling underneath the vehicle. They are extremely useful for freeing or towing off-road vehicles that are prone to getting stuck, and many owners upgrade the size of them for easier use.
Toyo - (“toy-yo”) is a type of popular off-road tires that was established in 1966.  Over the last few decades, ToyoTires has become one of the go-to off-road tire that are made in the USA at their Bartow County, Georgia facility.
TPI - acronym for “tuned-port fuel injection”.
Track - Distance between two wheels (front or rear) that are on the same axle and measured from the centerpoints of the wheels/tires.  
Trail Boss - The leader of a trail ride.
Trailer Queen - a vehicle that's built primarily for show and is trailered to events.


Transfer Case - The heart of a four-wheel-drive or all-wheel-drive system is the transfer case. It is often a box that simply transfers power from the transmission to the front and rear axles through the drive shafts when engaged. Essentially, when you put a vehicle into 4x4 or AWD, it is the transfer case you are utilizing to shift power to all four wheels. It’s also used to select low range, allowing drivers to access the vehicle’s crawl ratio when off-roading.
TTB - Twin-Traction Beam, a type of Ford front suspension that utilizes an axle assembly with pivot points, allowing the tires to move independently.
Tunnel Ram - Intake manifold with a large plenum and long, straight runners, used for high-rpm engines.
Turned Turtle - A truck that's rolled upside down.
Two-Bolt Main - Engine block with its main crankshaft caps held in place by two bolts.
Two-Wheeling - When tires lift off the ground during a tricky maneuver. Syn. bicycling.

U-bolt U-shaped bolt commonly used to attach an axle housing to a leaf-spring pack.
U-joint Mechanical joint that can transmit rotary motion while swiveling. Used at both ends of a driveshaft to transmit power from the transfer case to the differential.
Understeer - Cornering condition where a truck's front tires lose grip before the rear tires, causing the front end to slide or push toward the outside of the corner.
Unglued - 1. Damaged or destroyed; a blown-up engine has become unglued. 2. The codriver's mental state following a rollover.

Vacuum Advance - Device that advances or retards ignition timing according to the degree of engine vacuum. At low engine speed, there is plenty of engine vacuum, so the ignition is advanced; at wide-open throttle, there is little vacuum, so the ignition remains at its original timing advance.
Vacuum Secondary's - Secondary carburetor barrels that are pulled open by engine vacuum.
Valve Lift - Circular, stemmed device used to control the airflow in and out of an engine; operated by the camshaft/pushrods/rocker arms.
Valvetrain - The valve lifters, pushrods, rocker arms, and valve springs.
Vapor-lock - Condition where fuel boils within the fuel line or carburetor, causing bubbles to form that impede the fuel flow or cause excessive fuel to flood the carburetor.
Variable-Ratio Steering - Power-steering box that varies the steering ratio. At low speeds, the steering response is quicker for maneuverability; at high speeds, the steering ratio is reduced for stability.
Ventilate the Block - To throw a connecting rod through the side of an engine block due to component failure or excessive revs.
Venturi - a carburetor barrel or throat with a slightly narrowed or hourglass shape to its interior. The small, narrowed area speeds up airflow and helps pull the fuel past the carburetor jets and into the air stream.  The purpose of the venturi in the carburetor is to increase the air velocity. The venturi in carburetors is used to measure airflow in an engine.
VIN - acronym for “vehicle identification number”, a serial number that identifies a vehicle that started in 1954 by the American automakers that served to track the cars they made. In 1969, a law was passed that required all cars have a visible VIN#.
Wail - To perform at peak power or efficiency.
Wheel Adapter - Metal plate with wheel studs that allows a wheel with one bolt pattern to be used on a truck with a dissimilar bolt pattern.
Wheelbase - the distance from the center of a truck's front wheel to the center of the rear wheel on the same side.  For example, the 2007 Chevrolet Silverado 1500 LT Crew Cab is available in a number of different wheelbase configurations: 119", 133", 143.5", and 157.5".
Wheel Travel - The total distance a wheel can move up and down; affected by suspension travel and wheel-well clearance. More wheel travel means a more flexible suspension and more potential traction.
White-Knuckle - An obstacle that is scary enough to make the driver grip the steering wheel extremely tight.
Winch Mount - a fitted or specially made housing that is designed to hold the winch on the front of a vehicle that is usually bolted to the frame or bumper assembly and frame.  
Winch Pull Rating - is a formula that determines the amount of weight a winch can pull on level ground without the help of a snatch block or other assistive devices.  A popular formula that is safe is to choose a winch that is rated for at least 1.5x the weight you need to pull.  
Windage Tray - an internal engine shield, mounted close to the crankshaft and intended to deflect oil away from the crank as it rotates.
Wiring Harness - Major part of a truck's electrical wiring system; a group of wires bundled together.
WOT - stands for “Wide Open Throttle”.
Wrist Pin - Hollow metal tubular pin that attaches the piston to the connecting rod.




Zerk Fitting - a nipplelike fitting on suspension, U-joints, and chassis parts, through which lubricant is pumped under pressure to lubricate the components' internals to operate at optimal performance.

T glossary
U glossary
V glossary
W glossary
X glossary
Y glossary
Z glossary
Transfer Case definition
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