Off-Road Definitions

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Word Definition

4 Hi all wheel drive for mild off-road conditions allows higher speed driving. 4H Can also be used on sandy conditions such as beaches where higher speeds result in a desired flotation effect.

4 Low all wheel drive for low speed, more extreme conditions requiring maximum power and traction. Low range can also be used in a higher gear on sandy terrain such as a beach.

A arm found on all IFS suspensions listed in this catalog except for the Ford TTB. There is one upper and one lower arm on each side. They have a balljoint on the outboard end and connect to the frame on the inboard end.

All-wheel drive In this document, All-wheel drive will be used to describe a system which is similar to part-time four-wheel drive, but has no or limited control over it's "modes" of operation. All-wheel drive is a common safety feature on cars, mini vans and sport-utility vehicles.

Antilock Brakes Electronically controlled, sensor-actuated braking system designed to minimize or eliminate brake locking. RWAL (real antilock) is standard on most pickups. 4WAL (four-wheel antilock) is usually offered as a factory option, and is sometimes standard. Four-channel antilock indicates that each wheel has its own sensor.

Approach angle Formed by drawing a line from the front tire’s contact patch to the tip of the front bumper, and by drawing a line from the rear tire’s contact patch to the tip of the rear bumper. The shorter the overhand, the greater the angle and the more maneuverable in uneven terrain.

Articulation the suspension's ability to follow varying terrain keeping all four wheels on the ground in a cross-axle situation.

Auto Lockers Differentials that lock automatically when traction is required and unlock when variable rotation of wheels on a hard surface takes place. When in operation, power is equally split.

Axle ratio Number of driveshaft revolutions per revolution of the axle shafts. Can be calculated by dividing the number of teeth on the axle ring gear by the number of teeth on the pinion gear.

Axles This term has two or more meanings. In it's simplest form, an axle is a rotating metal shaft which drives a wheel. This is also called a shaft or axle shaft. It may be inside a housing, or exposed such as a CV axle (Referring to the Constant Velocity joints on both ends) on front-wheel drive cars. An axle may only provide rotating force to drive a wheel, or may also carry some of the weight of the vehicle. It is connected to a differential. Axle is also used as a general term referring to an axle housing. For example, someone speaking about the "rear axle" is talking about the axle housing, differential, axle shafts and sometimes the brakes.

Brake Horsepower A measure of power per mile found more often in European specs. Calculated: rpm x torque (lb-ft) / 5,250

Break Over the angle at which you can clear an obstacle without 'hanging up' between the axles, this is the point at which the underside of the vehicle would drag.

Bump steer Caused by a number of alignment problems, bump steer is when a vehicle darts or wanders excessively when operated on a less than ideal driving surface... in other words, it takes a concentrated effort to keep the vehicle in a straight line.

Camber The inward or outward tilt of the front tires as viewed from the front. Inward tilt is negative, outward tilt is positive. Camber is used to distribute load across the entire tread. Improper camber makes the tire wear on one edge, and causes the vehicle to pull to the side that has the most positive camber.

Caster The fore or aft slope of the steering axis. The steering axis is a line drawn through the upper and lower ball joints of the knuckle. Positive caster is when the bottom of the steering axis line is in front of the tire's contact patch. Zero caster is when the steering axis is at 0o. Positive caster ensures good stability, helps maintain straight-ahead direction and promotes steering wheel self-centering. Too much positive caster causes hard steering, excessive road shock and shimmy.

Centerlink A centerlink is found on IFS vehicles that have upper and lower control arms. It is a piece of steering linkage that connects the pitman and idler arms. A tie rod connects to each end of the centerlink. On some lifted trucks, the Original Equipment (OE) centerlink is replaced by a "dropped" centerlink.

Centre Differentials a full-time 4WD vehicle needs a centre differential to prevent wind up between front and rear axles - this being caused by the differential rotational speed on opposing wheels caused by cornering. In these vehicles the differential lock locks the front and rear drop shafts when going off-road.

CNC Stands for "Computerized Numerical Control". Term describes a type of control system used on a piece of manufacturing equipment. CNC machines offer unsurpassed accuracy and repeatability.

Compression travel A measurement of the amount the suspension will compress before it bottoms-out against its travel stop. This travel stop is also called a "bump stop" and "jounce stop".

Computerized Numerical Control a type of control system used on a piece of manufacturing equipment. CNC machines offer unsurpassed accuracy and repeatability.

Control arm Control arms, also called "A-arms" because of their shape, are found on all IFS suspensions listed in this catalog except for the Ford TTB. There is one upper and one lower arm on each side. They have a balljoint on the outboard end and connect to the frame on the inboard end.

CSS Stands for Centerlink Stabilizing System. A dropped centerlink tends to pivot fore and aft excessively when turning force is applied. The CSS uses one or two links to tie the centerlink to a crossmember and prevent this excessive movement.

CV axle Constant Velocity axle. With a control arm style IFS, they are the rubber or plastic booted axle shaft assemblies (one per side) that bolt to the differential housing flange on the inboard end, and mate to the hub / knuckle on the outboard end.

CVR Constant Voltage Regulator

Departure angle Formed by drawing a line from the front tire’s contact patch to the tip of the front bumper, and by drawing a line from the rear tire’s contact patch to the tip of the rear bumper. The shorter the overhand, the greater the angle and the more maneuverable in uneven terrain.

Differential A device that takes input from one rotating shaft, and distributes the energy between two output shafts. These are found in all automobiles, two or four-wheel drive. It's purpose is to apply driving force to the wheels, and allow for different rotational speeds while the vehicle is turning. (More on that later!) Differentials are found in axle housings, transfer cases and in transmissions (transaxles - almost all front-wheel drive cars).

DOM Stands for Drawn Over Mandrel. The term specifies a certain type of tubular steel that has exceptional strength, forming, and welding characteristics

DOT (Federal) Department Of Transportation

Drag link A piece of steering linkage that connects to a pitman arm on the upper end and a tie rod or knuckle on the lower end. On lifted vehicles, sometimes an Original Equipment (OE) drag link is replaced by a "dropped" drag link to reduce linkage angle.

Drive line Another rotating metal shaft. This one delivers power from the transmission or transfer case to the differentials. It also has a number of parts including u-joints, yokes, slip-joints and carrier bearings. Also called a propeller shaft sometimes.

Drive shaft Another rotating metal shaft. This one delivers power from the transmission or transfer case to the differentials. It also has a number of parts including u-joints, yokes, slip-joints and carrier bearings. Also called a propeller shaft sometimes.

Driveshaft angle The angle of the driveshaft in relation to the pinion yoke (at the differential) or the output yoke (at the transfer case). Driveline vibration, bind-free driveshaft operation and shaft length are influenced by driveshaft angle.

Extension travel A measurement of the amount the suspension will extend before it tops-out against it's travel stop.

Fuel Injection Electronically controlled fuel induction, either single-point (cheaper, less complex, less precise) or multi-point (more complex more precise and costlier).

Full-time four-wheel drive As indicated by the name, this system is always in four-wheel drive. Because of differentials in both drive axles and the transfer case (described below) it is possible to drive on high traction surfaces without causing damage to the vehicle. This system also includes a manual "locked" mode which makes it act like a part-time system in the four-wheel drive mode.

GCWR Gross Combined Weight Rating, measured as curb weight _ payload + towing capacity.

GVWR Gross Vehicle Weight Rating, measured as curb weight + payload

High Range all wheel drive for mild off-road conditions allows higher speed driving. 4H Can also be used on sandy conditions such as beaches where higher speeds result in a desired flotation effect.

Idler arm An idler arm is found on IFS vehicles that have a centerlink. The idler arm supports one end of the centerlink while the pitman arm supports the other.

Knuckle An iron or steel casting at the outboard ends of the axles that the spindle / hub / wheel assembly connects to. Replacement knuckles are used on lifted IFS vehicles when the lower control arms are lowered, but the upper control arms cannot be lowered.

Limited Slip a limited slip differential limits this speed difference by mechanical intervention in a way that permits only a certain amount of slip to take place. The action is automatic, in most cases providing sufficient power to enable one to clear the obstacle.

Limited-Slip Differential a limited slip differential limits this speed difference by mechanical intervention in a way that permits only a certain amount of slip to take place. The action is automatic, in most cases providing sufficient power to enable one to clear the obstacle.

Locking Differentials These use a mechanical locking device operated by the driver, when locked both axles turn at the same speed. May be pneumatic, hydraulic or electronic. If used when turning on a hard surface a characteristic scrubbing noise will be heard from the locked inner wheel. Pronounced use of this nature will result in accelerated wear.

Low Range all wheel drive for low speed, more extreme conditions requiring maximum power and traction. Low range can also be used in a higher gear on sandy terrain such as a beach.

Low-range ratio Gear reduction via a gear set in the transfer case. Generally speaking, the lower the low range ratio, the better its rock-crawling ability, and the greater the vehicle’s ability to mount taller tires and still have sufficient gearing for trail use.

Manual Differentials These use a mechanical locking device operated by the driver, when locked both axles turn at the same speed. May be pneumatic, hydraulic or electronic. If used when turning on a hard surface a characteristic scrubbing noise will be heard from the locked inner wheel. Pronounced use of this nature will result in accelerated wear.

Manual Locking Differentials These use a mechanical locking device operated by the driver, when locked both axles turn at the same speed. May be pneumatic, hydraulic or electronic. If used when turning on a hard surface a characteristic scrubbing noise will be heard from the locked inner wheel. Pronounced use of this nature will result in accelerated wear.

Manual Locking Differentials These use a mechanical locking device operated by the driver, when locked both axles turn at the same speed. May be pneumatic, hydraulic or electronic. If used when turning on a hard surface a characteristic scrubbing noise will be heard from the locked inner wheel. Pronounced use of this nature will result in accelerated wear.

Maximum towing capacity The maximum weight the vehicle is rated to tow. Based on engine power, gearing, cooling capability, rear spring rates and hitch quality, among other things.

Minimum ground clearance The distance from the ground to the lowest point of the chassis

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Word	Definition
4 Hi	all wheel drive for mild off-road conditions allows higher speed driving. 4H Can also be used on sandy conditions such as beaches where higher speeds result in a desired flotation effect.
4 Low	all wheel drive for low speed, more extreme conditions requiring maximum power and traction. Low range can also be used in a higher gear on sandy terrain such as a beach.
A arm	found on all IFS suspensions listed in this catalog except for the Ford TTB. There is one upper and one lower arm on each side. They have a balljoint on the outboard end and connect to the frame on the inboard end.
All-wheel drive	In this document, All-wheel drive will be used to describe a system which is similar to part-time four-wheel drive, but has no or limited control over it's "modes" of operation. All-wheel drive is a common safety feature on cars, mini vans and sport-utility vehicles.
Antilock Brakes	Electronically controlled, sensor-actuated braking system designed to minimize or eliminate brake locking. RWAL (real antilock) is standard on most pickups. 4WAL (four-wheel antilock) is usually offered as a factory option, and is sometimes standard. Four-channel antilock indicates that each wheel has its own sensor.
Approach angle	Formed by drawing a line from the front tire’s contact patch to the tip of the front bumper, and by drawing a line from the rear tire’s contact patch to the tip of the rear bumper. The shorter the overhand, the greater the angle and the more maneuverable in uneven terrain.
Articulation	the suspension's ability to follow varying terrain keeping all four wheels on the ground in a cross-axle situation.
Auto Lockers	Differentials that lock automatically when traction is required and unlock when variable rotation of wheels on a hard surface takes place. When in operation, power is equally split.
Axle ratio	Number of driveshaft revolutions per revolution of the axle shafts. Can be calculated by dividing the number of teeth on the axle ring gear by the number of teeth on the pinion gear.
Axles	This term has two or more meanings. In it's simplest form, an axle is a rotating metal shaft which drives a wheel. This is also called a shaft or axle shaft. It may be inside a housing, or exposed such as a CV axle (Referring to the Constant Velocity joints on both ends) on front-wheel drive cars. An axle may only provide rotating force to drive a wheel, or may also carry some of the weight of the vehicle. It is connected to a differential. Axle is also used as a general term referring to an axle housing. For example, someone speaking about the "rear axle" is talking about the axle housing, differential, axle shafts and sometimes the brakes.
Brake Horsepower	A measure of power per mile found more often in European specs. Calculated: rpm x torque (lb-ft) / 5,250
Break Over	the angle at which you can clear an obstacle without 'hanging up' between the axles, this is the point at which the underside of the vehicle would drag.
Bump steer	Caused by a number of alignment problems, bump steer is when a vehicle darts or wanders excessively when operated on a less than ideal driving surface... in other words, it takes a concentrated effort to keep the vehicle in a straight line.
Camber	The inward or outward tilt of the front tires as viewed from the front. Inward tilt is negative, outward tilt is positive. Camber is used to distribute load across the entire tread. Improper camber makes the tire wear on one edge, and causes the vehicle to pull to the side that has the most positive camber.
Caster	The fore or aft slope of the steering axis. The steering axis is a line drawn through the upper and lower ball joints of the knuckle. Positive caster is when the bottom of the steering axis line is in front of the tire's contact patch. Zero caster is when the steering axis is at 0o. Positive caster ensures good stability, helps maintain straight-ahead direction and promotes steering wheel self-centering. Too much positive caster causes hard steering, excessive road shock and shimmy.
Centerlink	A centerlink is found on IFS vehicles that have upper and lower control arms. It is a piece of steering linkage that connects the pitman and idler arms. A tie rod connects to each end of the centerlink. On some lifted trucks, the Original Equipment (OE) centerlink is replaced by a "dropped" centerlink.
Centre Differentials	a full-time 4WD vehicle needs a centre differential to prevent wind up between front and rear axles - this being caused by the differential rotational speed on opposing wheels caused by cornering. In these vehicles the differential lock locks the front and rear drop shafts when going off-road.
CNC	Stands for "Computerized Numerical Control". Term describes a type of control system used on a piece of manufacturing equipment. CNC machines offer unsurpassed accuracy and repeatability.
Compression travel	A measurement of the amount the suspension will compress before it bottoms-out against its travel stop. This travel stop is also called a "bump stop" and "jounce stop".
Computerized Numerical Control	a type of control system used on a piece of manufacturing equipment. CNC machines offer unsurpassed accuracy and repeatability.
Control arm	Control arms, also called "A-arms" because of their shape, are found on all IFS suspensions listed in this catalog except for the Ford TTB. There is one upper and one lower arm on each side. They have a balljoint on the outboard end and connect to the frame on the inboard end.
CSS	Stands for Centerlink Stabilizing System. A dropped centerlink tends to pivot fore and aft excessively when turning force is applied. The CSS uses one or two links to tie the centerlink to a crossmember and prevent this excessive movement.
CV axle	Constant Velocity axle. With a control arm style IFS, they are the rubber or plastic booted axle shaft assemblies (one per side) that bolt to the differential housing flange on the inboard end, and mate to the hub / knuckle on the outboard end.
CVR	Constant Voltage Regulator
Departure angle	Formed by drawing a line from the front tire’s contact patch to the tip of the front bumper, and by drawing a line from the rear tire’s contact patch to the tip of the rear bumper. The shorter the overhand, the greater the angle and the more maneuverable in uneven terrain.
Differential	A device that takes input from one rotating shaft, and distributes the energy between two output shafts. These are found in all automobiles, two or four-wheel drive. It's purpose is to apply driving force to the wheels, and allow for different rotational speeds while the vehicle is turning. (More on that later!) Differentials are found in axle housings, transfer cases and in transmissions (transaxles - almost all front-wheel drive cars).
DOM	Stands for Drawn Over Mandrel. The term specifies a certain type of tubular steel that has exceptional strength, forming, and welding characteristics
DOT	(Federal) Department Of Transportation
Drag link	A piece of steering linkage that connects to a pitman arm on the upper end and a tie rod or knuckle on the lower end. On lifted vehicles, sometimes an Original Equipment (OE) drag link is replaced by a "dropped" drag link to reduce linkage angle.
Drive line	Another rotating metal shaft. This one delivers power from the transmission or transfer case to the differentials. It also has a number of parts including u-joints, yokes, slip-joints and carrier bearings. Also called a propeller shaft sometimes.
Drive shaft	Another rotating metal shaft. This one delivers power from the transmission or transfer case to the differentials. It also has a number of parts including u-joints, yokes, slip-joints and carrier bearings. Also called a propeller shaft sometimes.
Driveshaft angle	The angle of the driveshaft in relation to the pinion yoke (at the differential) or the output yoke (at the transfer case). Driveline vibration, bind-free driveshaft operation and shaft length are influenced by driveshaft angle.
Extension travel	A measurement of the amount the suspension will extend before it tops-out against it's travel stop.
Fuel Injection	Electronically controlled fuel induction, either single-point (cheaper, less complex, less precise) or multi-point (more complex more precise and costlier).
Full-time four-wheel drive	As indicated by the name, this system is always in four-wheel drive. Because of differentials in both drive axles and the transfer case (described below) it is possible to drive on high traction surfaces without causing damage to the vehicle. This system also includes a manual "locked" mode which makes it act like a part-time system in the four-wheel drive mode.
GCWR	Gross Combined Weight Rating, measured as curb weight _ payload + towing capacity.
GVWR	Gross Vehicle Weight Rating, measured as curb weight + payload
High Range	all wheel drive for mild off-road conditions allows higher speed driving. 4H Can also be used on sandy conditions such as beaches where higher speeds result in a desired flotation effect.
Idler arm	An idler arm is found on IFS vehicles that have a centerlink. The idler arm supports one end of the centerlink while the pitman arm supports the other.
Knuckle	An iron or steel casting at the outboard ends of the axles that the spindle / hub / wheel assembly connects to. Replacement knuckles are used on lifted IFS vehicles when the lower control arms are lowered, but the upper control arms cannot be lowered.
Limited Slip	a limited slip differential limits this speed difference by mechanical intervention in a way that permits only a certain amount of slip to take place. The action is automatic, in most cases providing sufficient power to enable one to clear the obstacle.
Limited-Slip Differential	a limited slip differential limits this speed difference by mechanical intervention in a way that permits only a certain amount of slip to take place. The action is automatic, in most cases providing sufficient power to enable one to clear the obstacle.
Locking Differentials	These use a mechanical locking device operated by the driver, when locked both axles turn at the same speed. May be pneumatic, hydraulic or electronic. If used when turning on a hard surface a characteristic scrubbing noise will be heard from the locked inner wheel. Pronounced use of this nature will result in accelerated wear.
Low Range	all wheel drive for low speed, more extreme conditions requiring maximum power and traction. Low range can also be used in a higher gear on sandy terrain such as a beach.
Low-range ratio	Gear reduction via a gear set in the transfer case. Generally speaking, the lower the low range ratio, the better its rock-crawling ability, and the greater the vehicle’s ability to mount taller tires and still have sufficient gearing for trail use.
Manual Differentials	These use a mechanical locking device operated by the driver, when locked both axles turn at the same speed. May be pneumatic, hydraulic or electronic. If used when turning on a hard surface a characteristic scrubbing noise will be heard from the locked inner wheel. Pronounced use of this nature will result in accelerated wear.
Manual Locking Differentials	These use a mechanical locking device operated by the driver, when locked both axles turn at the same speed. May be pneumatic, hydraulic or electronic. If used when turning on a hard surface a characteristic scrubbing noise will be heard from the locked inner wheel. Pronounced use of this nature will result in accelerated wear.
Manual Locking Differentials	These use a mechanical locking device operated by the driver, when locked both axles turn at the same speed. May be pneumatic, hydraulic or electronic. If used when turning on a hard surface a characteristic scrubbing noise will be heard from the locked inner wheel. Pronounced use of this nature will result in accelerated wear.
Maximum towing capacity	The maximum weight the vehicle is rated to tow. Based on engine power, gearing, cooling capability, rear spring rates and hitch quality, among other things.
Minimum ground clearance	The distance from the ground to the lowest point of the chassis