Articles and Information on Rear End Related Topics
The following resources are made available as a service to our customers and anyone who finds them useful.
While every effort is made to ensure accuracy, we do not guarantee it, and cannot take responsibility for any
mechanical problems or damage that may result from relying on information provided here.
Differential Expressions
ABS: Anti-Lock Braking System
ADDITIVE: Friction modifier used in posi-tracs to help the clutches work smoothly and prevent chattering.
AFTERMARKET: Vehicle parts or equipment not manufactured by OE (original equipment) manufacturer.
AIR LOCKER: An on demand locking differential actuated by compressed air.
BEARING PRELOAD: Preloading is nothing more than removing all the clearance so that the bearing holds the rotating part absolutely rigid. Because torque and other forces may distort the parts in question, the bearing may be adjusted even tighter than needed to simply remove clearance. This increases the friction and creates a little more drag. For the bearing that require clearance, the correct amount of preload is vital.
BILLET: A part machined from a forged piece of metal rather than a casting.
CARDAN JOINT: The original name for the common universal joint, named for the 16th century Italian mathematician, Jerome Cardan, who established the basic principle of operation.
CARRIER BREAK: As the gear ratio gets lower (numerically higher), the pinion gear gets smaller. This means that the ring gear teeth must move toward the pinion centerline. This can be accomplished by making the pinion thicker, or by altering the carrier. Both methods are used, but the term refers to when the dimension (thickness) of the ring gear flange on the carrier is altered. There might be two or three carrier breaks for an axle with a wide range of available gear ratios. This can add extra expense to some ratio changes, most often when going from high to (numerically low) ratio.
CORPORATE AXLE: An axle built by the vehicle manufacturer, or exclusively for the vehicle manufacturer.
CROWN WHEEL: Another word for ring gear; common terminology in the early days of motoring here and still common in England.
CV-JOINT (CONSTANT VELOCITY JOINT) Several types exist, including the six ball Rzeppa (pronounced “Cheppa”) joint, the similar Birfield type, the four-ball Bendix type and the Herrington –type consisting of two Cardan or “ u joints.” The result of all of these is the smooth transmission of power with no vibration. They are used on drive shafts and steering axles.
ENDPLAY: As on a shaft. The shaft has movement along its longitudinal axis.
FULL-FLOATER: A full floating axle, which is one where the weight of the vehicle is borne by a separate sub axle and bearings rather than the axle shaft itself A.K.A a “floater.”
GCVWR: Gross Combined Vehicle Weight Rating. The maximum weight for a vehicle, its cargo and towed load.
HIGH GEARING: Numerically low gear ratios. Generally speaking, ratios from 2.50:1 to 3.54:1 are considered “high.” See also “Tall Gearing”
HYPOID GEARS: The ring and pinion gears are cut so that the pinion is driving above or below the centerline of the ring gear. This increases strength but also increases parasitic drag and increases heat.
HYPOID LUBRICANTS: Lubricants formulated for use in hypoid gear sets. These contain EP (extreme pressure) additives to prevent galling or abnormal wear under the extreme conditions imparted by hypoid gear sets. IFS: Independent front suspension. It can be with or without a system to drive the wheel, i.e., a four-wheel drive.
LIMITED SLIP: A traction aiding differential that will supply a percentage of torque to the tire with the most traction.
LOCKER: A traction aiding differential that will provide 100 percent of the torque to either axle, or both.
LOW GEARING: Numerically high gear ratios. Generally speaking, from 4.10:1 to about 6.13:1 (pretty near as low a ratio as you can find for light duty truck and SUV axles) are considered low gears. Lower then 4.88:1 is considered “super” low. Ratios from 3.54:1 to 4.10: are regarded as moderately low.
NOS: New old stock. Old parts but never used and still in their original boxes.
OEM: Original Equipment Manufacturer. Also “OE” A term sometimes used to describe a stock vehicle or its parts.
PINION: The input drive for the differential, a shaft with a small gear attached. The “spider” gears in an open differential are also called pinions.
PINION ANGLE: The angle of the differential input pinion in relation to the horizontal position.
POSI-TRAC: Slang for limited slip differential. Named after GM’s “Posi-Traction” unit, which was built by Eaton.
PUMPKIN: Slang for the removed part of a removed carrier differential, such as a Ford 9 inch or a Toyota.
REVERSE CUT RING GEAR: A gear set designed to run backwards compared to a rear axle with the torque applied to the strongest point of the ring gear, namely the convex side of the teeth. A reverse cut ring gear is a mirror image of a standard cut unit.
RING GEAR: A circular gear in the axle housing that provides the axle gear ratio in combination with the pinion gear.
SEMI-FLOAT: An axle that support the weight on the axle shaft as well as driving the wheel with it.
SPOOL: A device that connects the two axles directly to the ring gear. There is no differential side to side, so a vehicle equipped with a spool will bark tires in turn and may become unmanageable in wet or snowy weather. Spools are usually reserved for competition vehicles not driven on the street.
STOCK: As delivered from the manufacturer unmodified,
OE
TALL GEARING: Numerically low gear ratios. Generally speaking, ratios from 2.50:1 to 3.54:1 are considered “high”
TORQUE: Torque is rotational force and is measured in pounds-feet (or Newton-meters I the metric system). It’s really force (weight) times distance and the common measurements use the same distance, one foot or one meter, but vary the force (weight). One pound-foot is measured by putting one pound on the opposite end of a bar one-foot long. Ten pounds-feet is equal to 10 pounds on the bar. With Newton-meters (NM), the concept is the same, but the units of measurement are different. The bar is a meter long (3.28 feet) with the force of one Newton. That’s not a fig bar, but a unit of measurement that combines weight and the force of gravity. One Newton equals 0.22 pounds, one Newton-meter equals about 1.35 pounds-feet.
TORQUE MULTIPLICATION AND GEARING: Each gearing device has an input speed. In an axle, if the pinion turns four times and the ring gear turns one time, that axle has a 4:1 ratio. In addition to reducing the output speed, the gears multiply the torque by the same amount. If 100 pounds-feet goes into an axle that has a 4:1 ratio, 400 pounds-feet comes out.
TORSION BAR: A type of spring. One end is solidly attached to a chassis member and the other end is attached to one of the control arms. This converts the up and down suspension movement of the suspension into twist on the torsion bar.
TRACTION: The conversion of engine torque into motion.
TTB: Twin Traction Beam. A ford semi-independent front suspension and drive system for 4x4s used from 1980 to 1997.
U-BOLT: The u-shaped bolt used to attach the axle to a leaf spring.
U-JOINT: Universal joint. A.k.a. Cardan joint.
|
|
|
