Encyclopedia for 4 Wheelers: A Through Z

Also known as a control arm, there are two types: upper and lower. This triangular suspension component gets its name because it pivots on the A-shaped chassis at two points: the wide end and the pointy end, which attaches to the spindle. Generally used on independent suspensions.

Stands for Anti-Lock Braking System. If forced to brake suddenly, an ABS helps equalize the wheel speed so you don't skid out of control. The system is electronically controlled and provides two options: a two-channel that only controls the rear wheels, and a four-channel that controls all wheels.

Also known as a toe-out on turns, this is the principle that the inner wheel will have greater steering control than the outer wheel because it travels a shorter distance.

The method of adding an extra leaf to the leaf spring to provide additional lift. It is an inexpensive lifting method, but will take away some of the ride quality.

This encompasses all parts and equipment that are not produced by the original, OE manufacturer.

When driving up an incline, it is the largest angle between the road and the vehicle before the front of the vehicle hits the road, whether it's the body, chassis, or mechanicals.

The total amount of amp hours, or ampere hours, it takes to run a particular electrical device.

See definition for Camber

This is also known as Articulation or Cross-Axled. It is the moment when one tire is at its lowest travel, the other tire is at its upper travel, and the axle is at a severe angle to the body.

When the suspension compresses and droops on one axle, leaving the axles at severe angles so the body remains reasonably level.

Articulation - The ability of a suspension to combine compression and droop on one axle.

The ratio, expressed as a percentage, of a tire's width to its height. In this case, the height equals the distance between the tread and the rim, while the width is the section width. This is the tire's profile.

An axle wrap occurs when the axle is twisted into an "S" shape by the combined power of torque and traction, which cause the nose of the differential to go up while going forward and down while going backward. When this happens, the spring stores all of the energy until the tire slips, causing the spring to forcefully snap back and putting extra strain on the U-joints and driveshafts. It is also known as an axle hop, since it can create a hopping feeling.

The distance between the mounting flange and the inside edge of a wheel. Also known as wheel offset.

One of the key components of a tire's construction, it's the area where the tire mates with the wheel. It uses a hoop of high tensile steel wires to anchor the belts and give the rim a firm grip.

On the bead section of a tire, it is the part with a smooth surface that seals against the rim to hold air.

This is a dense wedge made out of rubber in the lower side-wall of the tire. It strengthens the area near the bead of the tire.

A wheel rim designed to keep the tire from abruptly deflating when used at low pressure.

Any 4x4 that's looking beaten down and worse for the wear but still runs pretty well.

When you add beef to a vehicle, you add strength to it or upgrade it.

Refers to vehicles constructed by the International Harvester Company. Short for Cornbiner.

This six-ball constant velocity joint was initially designed in the 1920s by Hans Rzeppa, but it's the later British manufacturer, Birfield Ltd., that stamped the name "Birfield" onto these complex and pricey CV joints. In the 1960s, it was presented for the Toyota land cruiser and to this day it is most commonly used by Toyota, and other Japanese 4x4, enthusiasts. It's unkown whether initial production was actually in Britain or Japan.

A sudden, "start/stop" thrust of the throttle.

A vehicle designed for trekking through the mud. Also a type of tire built for off road mud use.

These keep spring leaves in alignment on top of one another. These are generally a better option than cinch type of clamps because they don't limit mobility.

The spot where the suspension completely compresses and meets the bump stops.

Reinforcing the chassis by shutting the open part of a "C" or "U" section. The extra material significantly strengthens it.

Refers to a vehicle that has been greatly modified. Short for "built-up."

This occurs when the suspension is bumped and forced to move, which in turn causes the steering system and steering wheel to go one direction or the other. This can occur to 4x4s at both low and high speeds, but is considerably more dangerous when going faster.

This is a much smaller type of bumper that is installed to control the upward movement of the wheel, or the compress point. Generally made of rubber or polyurethane.

Stands for Center Axle Disconnect. It is designed to minimize the parasitic drag of the front axle by using a splined, sliding collar to separate a differential from a front axle shaft. It also stops the driveshaft from turning in 2WD and is another option for locking front hubs. A CAD system can only be used on a vehicle with open differentials because it permits the spider gears and differential side to rotate. Do not use a CAD system with a limited slip or locker because the left axle will control the driveshaft and ring and pinion, which will then cause your vehicle to vibrate when you drive at higher speeds.

On a leaf spring, it is the curve or arched part. This term can also be used to describe when the top of a front tire is tilting one way or the other. When looking at a tire from the front, a tire that tilts out would be described as having positive camber, while a tire tilting in would have negative camber.

When a vehicle suddenly veers one way or the other, it enhances the camber. This increase is the camber roll.

This is a common type of universal joint that gets its name from Jerome Cardan, an Italian mathematician from the 1500s who developed its key operational procedures. Also known as a Spicer-style universal joint.

When the steering access slants. If the top pivot tilts from the vertical towards the rear, then it is known as positive castor. The opposite would be known as negative castor.

This controls the balance of a vehicle and describes the spot where all planes are balanced equally. The lower the center of gravity is, the more difficult it is to roll the vehicle. Generally, the center of gravity can be found slightly in front of the mathematical center of the vehicle, one to two feet above the ground.

This refers to any little pieces of tread that fly off of the tire. This is generally caused by the friction and heat of day-to-day use, but it can also be caused by regular rock crawling or tire siping.

Chunk - When a tire throws off small pieces of tread.

The distance a suspension travels above the static ride height.

The section of the tire that meets with the ground, providing traction for the vehicle. This section is different for each tire based on size and pressure.

This type of steering system uses a tie rod to connect the two steering knuckles at the wheel ends. The steering input is attached to one of the knuckles by a drag link from the steering box.

Crossover Steering - The steering system in which the two steering knuckles at the wheel ends are tied together directly with one rod called the tie rod.

A vehicle designed for all wheel drive. Generally a car or minivan platform.

Also see articulated. A vehicle is cross-axled if the rear and front axles are oppositely articulated.

This ratio factors in the transfer case low range, first gear, and axle ratio to determine the peak multiplied lowest ratio gear. In the case that another gearing device is in use, it must be factored in as well. Also called the final drive ratio.

Stands for Constant Velocity joint and encompasses several types, including Birfield, Bendix, Rzeppa, and Herrington. These joints are used on steering axles and driveshafts to ensure there is no vibration with the transmission of power.

Any solid object that is heavy enough to act as an anchor and withstand the weight applied during winching.

When the steering vibrates rigorously.

See definition of Low Gearing.

The difference between the radius of a tire when it's unloaded and the radius when it's fully loaded. Also a term for the compression of a spring.

When descending an incline, it is the largest angle between the road and the vehicle before the rear of the vehicle hits the road and drags its tail.

A tire's capacity to drive in a straight line despite any irregularities in the road.

A steering rod that attaches the tie rod to the steering box Pitman arm.

Also known as jounce, this is how far a suspension travels below a vehicle's normal height ride.

This is lower than a stock Pitman arm to minimize bump steer and drag link angularity.

The maximum amount of time a device can be used before damage starts to occur.

The piece at the end of the spring that is looped for spring mounting or bushing installation. Also applies to the looped ends of ropes and cables.

The distance between the center of one eye to the other of an unloaded leaf spring.

Two types: a Hawse fairlead and a Roller fairlead, both of which guide the winch cable. A Hawse fairlead uses a basic opening with smooth edges to guide it, while a Roller fairlead uses rollers that are fixed on the top, bottom, and sides.

To calculate the free arch of an unloaded leaf spring, draw an imaginary line between the centers of the two eyes. Then take the distance between that line and the top of the inside of the spring, and that’s the free arch.

Free Arch - The distance between the top of the inside of a leaf spring to an imaginary line drawn between the center of the two eyes. The spring is unloaded.

The length of a coil spring when it is free of any weight, or unloaded.

An axle that does not support the weight of the vehicle. Instead, it is supported by a separate stub axle and bearings.

Stands for Gross Combined Vehicle Weight Rating. It combines the maximum weights of the vehicle, its cargo, and its tow load to get the maximum total weight.

Gauges the heavy-duty meter.

Any of the lower gears. For example, “granny-granny” is often used to refer to first gear, low range.

The tire before it has actually been formed awaiting molding and heating, along with its other components.

To spectacularly obliterate a mechanical part

The traction of a tire on ground surface, also known as the friction coefficient.

A component that reinforces the point where two structural members meet.

Stands for Gross Vehicle Weight Rating, it’s the greatest amount of weight for a vehicle plus its cargo.

Describes any component that has been really battered or thrashed.

Hung up either on the center of the vehicle or the axle.

This generally applies to cables and straps, but it is also used to express a gain in traction.

Gear ratios that are numerically low, generally from 2.50:1 to 3.54:1. Also see Tall Gearing.

A hypoid axle that has a reverse cut ring gear. Once mounted in an axle, it places the pinion above the centerline rather than below it. A reverse cut ring and pinion is 15% stronger than a standard one when used in a front axle, but 15% weaker when used on a back axle.

Also known as “Hydro’ed” and “Hydraulic’ed,” it occurs when the engine cannot turn because water has gotten into the cylinder and doesn’t allow it to compress.

Independent Front Suspension

Instead of attaching the drag link at the knuckles of the tie rod, like in a crossover system, it attaches at the inboard of the knuckles.

A steering system in which the drag link is attached to the opposite axle knuckle and connected to the original axle with a short tie rod. It is also known as the “Haltenberger” system from numerous Jeep coilers.

When you elevate a vehicle for the purpose of trail clearance or clearing for the tires.

A differential that provides a specified amount of torque to whichever tire gets the most traction in order to further aid the traction.

When dealing with an obstacle, it is the path that gives the most traction and clearance over or through the obstacle.

When using a winch, it is how much pull it can produce. While this can be measured in several ways, most of the time it is taken from the first layer of cable, with an adequate battery if it’s electric.

How quickly the drum spools the cable, generally in feet per minute in the Metric-averse USA. The different variables for line speed include gearing, motor power, load, and which layer of cable is used.

Any vehicle that has a locker, or lockers.

A differential that increases traction by focusing all of the torque on either axle, or both.

Gear ratios that are numerically high, generally from 4.10:1 to 7.17:0. Also known as Deep Gearing, this is basically the lowest ratio you can find for light duty trucks and SUVs. Anything lower than 4.88:1 is “super” low, while 3.54 to 4.10 is moderately low.

Low range

On a leaf spring, it is the first, or primary, leaf. Generally, this is the only one with an eye, though occasionally the second leaf will have one too.

Another name for tires, also known as “zapatos” or “skins.” It is especially used for the very large tires.

A word that originated in the Army, it can now be used to describe something moving under power.

It is when the second leaf of a leaf spring wraps around the eye of the main leaf. Originally used in the Army, hence the name, it was designed so that the leaf spring could still operate in the event that the main leaf broke.

A suspension that locates the axle with numerous links.

When you nail the accelerator, or “punch it,” you completely depress it.

A guard for the rocker panel.

Stands for New Old Stock. It refers to any old parts that are still considered new because they have never been used and are even still in the original boxes.

NOS - New old stock. Old parts but never used and still in their original boxes, as this 1951 dated Mopar part.

Stands for Noise, Vibration, and Harshness.

Also known as “OE,” stands for Original Equipment Manufacturer. It describes any parts that were part of the stock vehicle.

Also known as sidehill, it’s when something is leaning sideways on a slope.

The point at the top of the winch drum where the cable spools off.

On a coil spring and select leaf spring suspensions, it’s the slanting link that locates the axle crossways.

When something breaks, like a winch cable.

Rather than using energized field coils, this basic motor uses two magnets. Because of this, the motor is more compact and provides a lower amp draw. Other than that, performance and power are basically the same as Series Wound motors. On the negative side, high loads will generate more heat and the larger the load, the shorter the duty cycle. And at sub-zero temperatures, there is less magnetic attraction and therefore less power. Generally, you can find these motors being used for low capacity winches.

It’s the measurement of how off-center the anchor pin is that locates the axle on the leaf spring.

On a differential, it’s the input drive. It can also be a shaft that has a small gear fastened to it, and it can be a name for the “spider” gears on an open differential.

The angle between the differential input pinion and the horizontal position.

Pinion Angle - The angle of the differential input pinion in relation to the horizontal position.

Fixes to the output shaft of the steering box to switch the movement of the steering box from rotating to lateral.

Describes how tightly wound a coil spring is. A spring with coils that are very close has less pitch, and vice versa. Can also be known as ramp.

This multi-piece gear set is named for the way the gears rotate around one another. At the center is the sun gear with 2-4 planet gears rotating around it, and they’re all surrounded by a ring gear.

Jargon for a limited slip differential. It gets its name from GM’s “Posi-Traction.”

A truck that is built to prerun desert race courses. It can also be used to describe a type of truck that is designed to speed through dirt. The truck can be a 4x4 or a 4x2, as long as it has yielding, long travel suspension that will withstand a lot of time in the air.

If the rate of a spring increases as it is compressed, it has a progressive rate.

Divides the amount of pressure being applied to the brakes between the front and the rear, generally with more pressure on the front brakes.

PTO powers winches or other devices with power from the engine. This mechanical device supplies the power either directly or through the drivetrain. Winch PTOs drive off either the transmission or the transfer case.

On a removable carrier differential, it’s the part that has been removed.

A long rod that connects two wheels with the attached tie rods on the ends, thus eliminating the need for the conventional steering linkage and box. The rod sits inside housing that is parallel to the ground, with teeth on one of its sides. Connected to the steering wheel through the steering column is a spur type gear. The wheels are then steered by the steering wheel input moving the rod left or right.

Rack and Pinion Steering - This system eliminates the conventional steering linkage and steering box.

On multi-link suspensions, they are the fore and aft locating arms. Generally this applies only to suspensions that have one fore and one aft locating arm, rather than two of each.

The angle between a vehicle’s midsection and the contact area of the tires to determine the amount of clearance.

For a spring, it is the weight, in pounds per inch, it takes to deflect it. For example, for one inch spring it would take 200 lbs to deflect it, so the rate would be 200 lbs/in.

When a compressed spring returns to its normal ride height, which is also known as the preset memory position.

Also known as the crown gear, this is the circular gear in the axle housing that, with the pinion gear, supplies the axle gear ratio.

Generally this is something to watch out for on lifted 4x4s with track bars that have a lot of angularity on the track rod. With the change in ride height, the position of one axle to the other is altered by the transverse track bar. This causes some steering input, which must be fixed by the driver.

Any path, paved or unpaved, that was created to be traveled on by motor vehicles.

When traveling on uneven ground, it’s how much the body of the vehicle leans.

Generally this affects long travel coil spring rigs when the steering of the vehicle is affected by body roll changing the position of the axle, forcing the driver to correct the steering.

Stands for Ramp Travel Index. This is a measurement of suspension and articulation. It is calculated by driving a single wheel up a ramp until you get to the point where one of the rear wheels lifts up. Then you measure the distance up the ramp level with the hub center and divide that by the vehicle’s wheelbase to get the RTI.

The height of a still vehicle with no active forces affecting it.

Also known as presetting, this occurs when the permanent height, or camber, of a spring is set. Specifically, it refers to the method of setting this position, or memory. To set the height, a spring is assembled and place in a press where it is compressed a fixed amount. This amount is generally set at a point past the normal deflection the spring will encounter.

The width of the tire from sidewall to sidewall. This is not the same as the tread width.

An axle that both supports weight on the axle shaft and drives the wheel with it.

Semi-Float - An axle that supports the weight on the axle shaft as well as driving the wheel with it.

A motor that uses field windings made of copper wire, which is wound over an iron core. In comparison to a magnet motor, it has a longer duty cycle, is more resistant to heat, is larger, and produces more power even though they have basically the same performance characteristics. They are generally used for higher capacity winches, especially in commercial operations.

This can be used to describe two things. First, it is the link on the end of a spring leaf that pivots, which permits the spring to flex and get longer or shorter. Second, it is a connector in winching that is either bow-shaped or d-shaped.

Created for PTO winches, which have a large disparity between the power of the electric motor and the power of the engine. This difference can cause key components to break. A shear pin is made to break before any other part will so you know when to back off. This is why it’s a great idea to always have a few shear pins handy.

When you want to compress the surface of a steel part and surface harden it, you shotpeen it by spraying steel shot at a high pressure on its surfaces. Can also be used on leaf springs and connecting rods.

Jargon for an automatic transmission.

The slits, or cuts, made in the tread block of a tire. They are put here, either by the manufacturer or by someone who adds it later, to allow movement, grip, and better performance on wet and icy roads.

Siping - Slits or cuts in the tread blocks that allow the blocks to move and grip.

In winching, it’s a high-capacity pulley.

In winching, it’s a recovery strap that uses kinetic energy.

Wrapping the layers of winching cable tightly and carefully around the drum. It can also be used to describe a solid carrier that directly connects the axles to the ring gear, taking the differential out of the equation.

To wrap the winch cable back around the winch drum.

To unwind the winch cable from the winch drum.

This person acts as an extra set of eyes for the driver from outside of the vehicle in tricky situations.

Generally past a winch’s maximum line pull, it’s the position where a winch halts under a load.

In an automatic transmission torque converter, it’s the amount of slippage rated by rpm, or the measure of the torque multiplication of the converter. It’s also known as Flash Stall, which is determined by the engine rpm of a vehicle going from a complete stop to full throttle.

Delivered and unmodified from the original manufacturer. Also see OEM.

The amount of vertical movement of a suspension that has the axle on a level plane.

Slang for transfer case or, in some parts of the world, transfer box.

When a part is bent into a u-shape, similar to that of a taco.

During a group trail ride, it’s the person who goes last to make sure that no one gets left behind.

Also see High Gearing, it describes gear ratios that are numerically low, generally from 2.50:1 to 3.54:1.

When the ends of each leaf on a leaf spring are tapered, it creates a softer rate spring and reduces friction. It can also be used to describe bore wear in an engine. Because there is generally more wear on the upper part of a cylinder, it tends to become taper shaped.

Stands for Throttle Body Injection. This fuel injection system uses throttle butterflies on top of the intake manifold to inject the fuel.

Connects two wheels to control the steering.

When you employ the most amount of braking pressure possible just before the point where the tires lockup.

Refers to the positions of the tires. If they are toe-in, it means the front edges are pointing towards each other, and vice versa for toe-out.

The force of the vehicle multiplied by the distance traveled, expressed in lbs-ft. Example: One pound of weight times one foot bar equals one lb-ft of torque.

Used in automatic transmissions as a fluid coupling/clutch. There are three main components: the impeller, the turbine, and the stator. The spinning impeller is driven by the engine to force transmission fluid against the turbine, which connects directly to the transmission and causes its blades to spin in the same direction. The stator is positioned between the two to direct the flow of oil.

Can occur on vehicles with lifted coil spring suspensions. It happens with the ride height is increased by the added torque from the tire grip.

A type of spring that translates the suspension’s vertical movement into a twist. It attaches to one of the chassis members and one of the control arms.

Also known as a Chevota, it is a sort of hybrid between a Chevrolet and a Toyota. Generally, it’s a Toyota vehicle with a Chevy engine installed.

Stands for Tuned Port Injection. It is a high performance, multiport fuel injection system by GM.

When a vehicle converts engine and drivetrain torque into motion.

Jargon used by four-wheeler enthusiasts to describe a road that has not been touched, or is unimproved.

Sometimes used in a disparaging way, it describes either a show rig that uses a trailer to travel, or rigs that use a trailer to get to and from four-wheeling locations.

Stands for Twin Traction Bean. It’s a semi-independent front suspension by Ford designed for 4x4s from 1980-1997.

Attaches and axle to a spring leaf, named because it’s in the shape of an “u”.

Short for universal joint. Also known as a Cardan joint.

The point at the bottom of the drum where the winching cable spools off.

This device is made of numerous plates in a silicone gel filled sealed case, plus input and output shafts. The plates are divided in half and alternate connections to the input and output shafts. Its purpose is to either transmit power or lock a center differential. If there is a discrepancy, the silicone gel thickens to couple the sides together.

On a tire tread, it’s the ratio of open areas to areas that contact the ground.

A suspension’s total amount of vertical movement, measured at the hub.

Another name for steel winch cable.

To make coil springs, a bar of metal is wound and tempered to create coils. The diameter of this metal is the wire size.

The instant when a part becomes irreparably deformed. Thought it may not be broken, it is weakened and will not function at maximum capacity.