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79-406: A four-wheel drive , also called 4×4 ("four by four") or 4WD , is a two-axled vehicle drivetrain capable of providing torque to all of its wheels simultaneously. It may be full-time or on-demand, and is typically linked via a transfer case providing an additional output drive shaft and, in many instances, additional gear ranges . A four-wheel drive vehicle with torque supplied to both axles

158-410: A center differential (or similar device). The definition notes that part-time systems may have a low range. Full-time AWD systems drive both front and rear axles at all times via a center (interaxle) differential. The torque split of that differential may be fixed or variable depending on the type of center differential. This system can be used on any surface at any speed. The definition does not address

237-408: A charging socket (therefore relying on the engine or regenerative braking to charge the batteries) are considered to be mild hybrids . Differential (mechanics) A differential is a gear train with three drive shafts that has the property that the rotational speed of one shaft is the average of the speeds of the others. A common use of differentials is in motor vehicles , to allow

316-427: A combination of the two. The most common types of internal combustion engines are: Most purely electric vehicles use batteries for energy storage and are referred to as battery electric vehicles . Vehicles with both internal combustion engines and electric motors are called hybrid vehicles . If a hybrid vehicle includes a charging socket, it is considered to be a plug-in hybrid , while vehicles that do not include

395-429: A differential, thus relying on wheel slip when cornering. However, for improved cornering abilities, many vehicles use a differential, which allows the two wheels to rotate at different speeds. The purpose of a differential is to transfer the engine's power to the wheels while still allowing the wheels to rotate at different speeds when required. An illustration of the operating principle for a ring-and-pinion differential

474-515: A four-wheel-drive passenger vehicle. The modern Geländewagen such as the Mercedes-Benz G-Class still feature some of the attributes, with the exception of fully independent suspension, since it can compromise ground clearance. The Unimog is also a result of Mercedes 4x4 technology. The first Russian-produced four-wheel-drive vehicle, also in part for civilian use, was the GAZ-61 , developed in

553-433: A low-grip surface under one wheel), an open differential can cause wheelspin in the tyre with less grip, while the tyre with more grip receives very little power to propel the vehicle forward. In order to avoid this situation, various designs of limited-slip differentials are used to limit the difference in power sent to each of the wheels. Torque vectoring is a technology employed in automobile differentials that has

632-412: A pointer which constantly pointed to the south, no matter how the chariot turned as it travelled. It could therefore be used as a type of compass . It is widely thought that a differential mechanism responded to any difference between the speeds of rotation of the two wheels of the chariot, and turned the pointer appropriately. However, the mechanism was not precise enough, and, after a few miles of travel,

711-528: A production GT sports car. While most 4WD systems split torque evenly, the Jensen split torque roughly 40% front, 60% rear by gearing the front and rear at different ratios. American Motors Corporation (AMC) acquired Kaiser's Jeep Division in 1970 and quickly upgraded and expanded the entire line of off-road 4WD vehicles. With its added roadworthiness, the top-range full-sized Grand Wagoneer continued to compete with traditional luxury cars . Partially hand-built, it

790-414: A system that applies torque to all four wheels (permanently or on-demand) or is targeted at improving on-road traction and performance (particularly in inclement conditions), rather than for off-road applications. Some all-wheel drive electric vehicles use one motor for each axle, thereby eliminating a mechanical differential between the front and rear axles. An example of this is the dual-motor variant of

869-532: A total of 41,674 units made by 1928. Daimler-Benz also has a history in four-wheel drive. After the Daimler Motoren Gesellschaft had built a four-wheel-driven vehicle called Dernburg-Wagen , also equipped with four-wheel steering , in 1907, that was used by German colonial civil servant, Bernhard Dernburg, in Namibia ; Mercedes and BMW, in 1926, introduced some rather sophisticated four-wheel drives,

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948-518: A truck with dual rear wheels on two rear axles, so actually having ten wheels, its configuration would still be formulated as 6x4. During World War II, the U.S. military would typically use spaces and a capital 'X' – as "4 X 2" or "6 X 4". Four-wheel drive (4WD) refers to vehicles with two axles providing torque to four axle ends. In the North American market, the term generally refers to a system optimized for off-road driving conditions. The term "4WD"

1027-422: A two-door roadster, a two-door pickup truck, and a four-door phaeton, all equipped with a transfer case that engaged the front wheels, powered by a 1.3-litre, two-cylinder, air-cooled OHV V-twin engine. The 1937 Mercedes-Benz G5 and BMW 325 4×4 featured full-time four-wheel drive, four-wheel steering, three locking differentials, and fully independent suspension. They were produced because of a government demand for

1106-454: A type of mechanical analogue computer, were used from approximately 1900 to 1950. These devices used differential gear trains to perform addition and subtraction. The Mars rovers Spirit and Opportunity (both launched in 2004) used differential gears in their rocker-bogie suspensions to keep the rover body balanced as the wheels on the left and right move up and down over uneven terrain. The Curiosity and Perseverance rovers used

1185-412: A wheel is slipping, and only activates when wheel slip is detected. Therefore, typically no mechanism exists to actively prevent wheel slip (i.e., locking the differential in advance of wheel slip is not possible); rather, the system is designed to expressly permit wheel slip to occur, and then to attempt to send torque to the wheels with the best traction. If preventing all-wheel slip is a requirement, this

1264-422: Is a limiting design. The architecture of an AWD/4WD system can be described by showing its possible operating modes. A single vehicle may have the ability to operate in multiple modes depending on driver selection. The different modes are: In addition to these basic modes, some implementations can combine these modes. The system could have a clutch across the center differential, for example, capable of modulating

1343-413: Is described as "all-wheel drive" (AWD). However, "four-wheel drive" typically refers to a set of specific components and functions, and intended off-road application, which generally complies with modern use of the terminology. Four-wheel-drive systems were developed in many different markets and used in many different vehicle platforms . There is no universally accepted set of terminology that describes

1422-441: Is distributed to all four wheels, a third or 'center' differential can be used to distribute power between the front and rear axles. The described system handles extremely well, as it is able to accommodate various forces of movement and distribute power evenly and smoothly, making slippage unlikely. Once it does slip, however, recovery is difficult. If the left front wheel of a 4WD vehicle slips on an icy patch of road, for instance,

1501-458: Is exceeded at the low-traction side. A fairly recent innovation in automobiles is electronic traction control . It typically uses a vehicle's braking system to slow a spinning wheel. This forced slowing emulates the function of a limited-slip differential, and by using the brakes more aggressively to ensure wheels are being driven at the same speed, can also emulate a locking differential. This technique normally requires wheel sensors to detect when

1580-489: Is frequently used to refer to a class of vehicles in general. Syntactically, the first figure indicates the total number of axle ends and the second indicates the number of axle ends that are powered. Accordingly, 4×2 means a four-wheel vehicle that transmits engine torque to only two axle ends: the front two in front-wheel drive or the rear two in rear-wheel drive . Similarly, a 6×4 vehicle has three axles, two of which provide torque to two axle ends each. If this vehicle were

1659-460: Is much less acceptable for 4WD vehicles, because 4WD vehicles have twice as many wheels with which to lose traction, increasing the likelihood that it may happen. 4WD vehicles may also be more likely to drive on surfaces with reduced traction. However, since torque is divided between four wheels rather than two, each wheel receives roughly half the torque of a 2WD vehicle, reducing the potential for wheel slip. Many differentials have no way of limiting

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1738-407: Is shown below. A relatively simple design of differential is used in rear-wheel drive vehicles, whereby a ring gear is driven by a pinion gear connected to the transmission. The functions of this design are to change the axis of rotation by 90 degrees (from the propshaft to the half-shafts) and provide a reduction in the gear ratio . The components of the ring-and-pinion differential shown in

1817-545: Is typically designated for vehicles equipped with a transfer case that switches between 2WD and 4WD operating modes, either manually or automatically. All-wheel drive (AWD) was historically synonymous with "four-wheel drive" on four-wheeled vehicles, and six-wheel drive on 6×6s , and so on, being used in that fashion at least as early as the 1920s. Today in North America, the term is applied to both heavy vehicles and light passenger vehicles. When referring to heavy vehicles,

1896-470: The British Rail Class 03 and British Rail Class 04 diesel shunting locomotives. In a motor vehicle , the powertrain consists of the source of propulsion (e.g. the engine or electric motor) and the drivetrain system which transfers this energy into forward movement of the vehicle. The powertrain consists of the prime mover (e.g. an internal combustion engine and/or one or more traction motors) and

1975-553: The Canadian Military Pattern trucks , of which 4x4s were by far the most prevalent of their various driveline configurations. All told, North America built about 1 + 1 ⁄ 2 million 4x4 driven vehicles during the war, Availability of certain critical components, such transfer cases and especially constant-velocity joints affected development. Though not used much on commercial vehicles, all-wheel drive vehicles all needed these; and they would use two or three times

2054-483: The Oldsmobile Toronado American front-wheel drive car. Locking differentials have the ability to overcome the chief limitation of a standard open differential by essentially "locking" both wheels on an axle together as if on a common shaft. This forces both wheels to turn in unison, regardless of the traction (or lack thereof) available to either wheel individually. When this function is not required,

2133-564: The Soviet Union in 1938. "Civilian use" may be a bit of a misnomer, as most, if not all, were used by the Soviet government and military (as command cars), but the GAZ-61-73 version is the first four-wheel-drive vehicle with a normal closed sedan body. Elements of the chassis were used in subsequent military vehicles such as the 1940 GAZ-64 and the 1943 GAZ-67 , as well as the postwar GAZ-69 , and

2212-542: The Tesla Model S , which controls the torque distribution between its two motors electronically. According to the SAE International standard J1952, AWD is the preferred term for all the systems described above. The standard subdivides AWD systems into three categories. Part-time AWD systems require driver intervention to couple and decouple the secondary axle from the primarily driven axle, and these systems do not have

2291-529: The k. u. k. Hofwagenfabrik Ludwig Lohner & Co. in Vienna in 1899, presented to the public during the 1900 World Exhibition in Paris. The vehicle was a series hybrid car that used an electric hub motor at each wheel, powered by batteries, which were in turn charged by a gasoline-engine generator. It was clumsily heavy, and due to its unusual status, the so-called Lohner–Porsche is not frequently given its credit as

2370-449: The "correct" time, so an ordinary clock would frequently have to be readjusted, even if it worked perfectly, because of seasonal variations in the equation of time. Williamson's and other equation clocks showed sundial time without needing readjustment. Nowadays, we consider clocks to be "correct" and sundials usually incorrect, so many sundials carry instructions about how to use their readings to obtain clock time. Differential analysers ,

2449-646: The American Four Wheel Drive Auto Company (FWD) of Wisconsin , founded in 1908. (not to be confused with the term "FWD" as an initialism for front-wheel-drive ) Along with the 1 1 ⁄ 2 - and 2-ton Nash Quad (see below), the 3-ton FWD Model B became a standard military four-wheel-drive truck for the U.S. Army in World War I. Some 16,000 FWD Model B trucks were built for the British and American armies during World War I – about half by FWD and

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2528-557: The G1, the G4, and G4 following. Mercedes and BMW developed this further in 1937. The American Marmon-Herrington Company was founded in 1931 to serve a growing market for moderately priced four-wheel-drive vehicles. Marmon-Herrington specialized in converting Ford trucks to four-wheel drive and got off to a successful start by procuring contracts for military and commercial aircraft refueling trucks, 4×4 chassis for towing light weaponry, and an order from

2607-495: The Iraqi Pipeline Company for what were the largest trucks built at the time. The early Marmon-Herringtons proved to be the exception to the rule — 4WD cars and trucks developed in the 1930s were mainly built for governments, with (future) warfare applications in mind. Dodge developed its first four-wheel-drive truck in 1934 — a military 1 + 1 ⁄ 2 ton designated K-39-X-4(USA), of which 796 units were built for

2686-489: The J1952 standard notes secondary classifications resulting in a total of eight systems, designated as: Two wheels fixed to the same axle (but on the opposite axle ends) need to turn at different speeds as a vehicle goes around a curve. The reason is that the wheel that is located on the inner side of the curve needs to travel less distance than the opposite wheel for the same duration of time. However, if both wheels are connected to

2765-597: The Jeep, and also inline-four powered, the Land Rover appeared at the Amsterdam Motor Show in 1948. Originally conceived as a stop-gap product for the struggling Rover car company, despite chronic underinvestment, it succeeded far better than their passenger cars. Inspired by a Willys MB – the ubiquitous WWII "jeep" – that was frequently run off-road on the farm belonging to chief engineer Maurice Wilks , Land Rover developed

2844-424: The U.S. Army in several configurations. Timken supplied front axles and transfer cases, added to militarized a civilian truck. The Timken transfer case was the first part-time design, that allowed the driver to engage or disengage four-wheel drive using a lever inside the cab. In spite of the limited 1930s U.S. military budgets, the '34 truck was liked well-enough that a more modern 1 + 1 ⁄ 2 ton truck

2923-465: The ability to vary the torque to each half-shaft with an electronic system; or in rail vehicles which achieve the same using individually motored wheels. In the case of automobiles, it is used to augment the stability or cornering ability of the vehicle. Non-automotive uses of differentials include performing analogue arithmetic . Two of the differential's three shafts are made to rotate through angles that represent (are proportional to) two numbers, and

3002-480: The amount of engine power that gets sent to their attached output shafts. As a result, if a tire loses traction on acceleration, either because of a low-traction situation (e.g., driving on gravel or ice) or the engine power overcomes available traction, the tire that is not slipping receives little or no power from the engine. In very low-traction situations, this can prevent the vehicle from moving at all. To overcome this, several designs of differentials can either limit

3081-442: The amount of slip (these are called 'limited-slip' differentials) or temporarily lock the two output shafts together to ensure that engine power reaches all driven wheels equally. Locking differentials work by temporarily locking together a differential's output shafts, causing all wheels to turn at the same rate, providing torque in case of slippage. This is generally used for the center differential, which distributes power between

3160-560: The angle of the third shaft's rotation represents the sum or difference of the two input numbers. The earliest known use of a differential gear is in the Antikythera mechanism, c. 80 BCE, which used a differential gear to control a small sphere representing the Moon from the difference between the Sun and Moon position pointers. The ball was painted black and white in hemispheres, and graphically showed

3239-422: The axis of its input shaft). A spur-gear differential has an equal-sized spur gears at each end, each of which is connected to an output shaft. The input torque (i.e. from the engine or transmission) is applied to the differential via the rotating carrier. Pinion pairs are located within the carrier and rotate freely on pins supported by the carrier. The pinion pairs only mesh for the part of their length between

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3318-472: The complete front-engine, four-wheel-drive system. The AMC Eagle was offered as a sedan , coupe , and station wagon with permanent automatic all-wheel drive passenger models. The new Eagles combined Jeep technology with an existing and proven AMC passenger automobile platform . They ushered a whole new product category of "sport-utility" or crossover SUV . AMC's Eagles came with the comfort and high-level appointments expected of regular passenger models and used

3397-440: The design or use of differentials include: During cornering, the outer wheels of a vehicle must travel further than the inner wheels (since they are on a larger radius). This is easily accommodated when the wheels are not connected , however it becomes more difficult for the drive wheels , since both wheels are connected to the engine (usually via a transmission). Some vehicles (for example go-karts and trams ) use axles without

3476-408: The dial could be pointing in the wrong direction. The earliest verified use of a differential was in a clock made by Joseph Williamson in 1720. It employed a differential to add the equation of time to local mean time , as determined by the clock mechanism, to produce solar time , which would have been the same as the reading of a sundial . During the 18th century, sundials were considered to show

3555-417: The differential can be "unlocked" to function as a regular open differential. Locking differentials are mostly used on off-road vehicles, to overcome low-grip and variable grip surfaces. An undesirable side-effect of a regular ("open") differential is that it can send most of the power to the wheel with the lesser traction (grip). In situation when one wheel has reduced grip (e.g. due to cornering forces or

3634-409: The differential to the wheel, at different speeds. The differential does this by distributing angular force (in the form of torque ) evenly, while distributing angular velocity (turning speed) such that the average for the two output shafts is equal to that of the differential ring gear . When powered, each axle requires a differential to distribute power between the left and right sides. When power

3713-528: The driver of getting out to lock hubs and having to manually select between 2WD and 4WD modes, it dominated all other makes in FIA rally competition. Gene Henderson and Ken Pogue won the Press-on-Regardless Rally FIA championship with a Quadra Trac-equipped Jeep in 1972. American Motors introduced the innovative Eagle for the 1980 model year. These were the first American mass-production cars to use

3792-430: The drivetrain - all of the components that convert the prime mover's power into movement of the vehicle (e.g. the transmission , driveshafts , differential and axles ); whereas the drivetrain does not include the power source and consists of the transmission, driveshafts, differential and axles. Most passenger cars and commercial vehicles are powered by either an internal combustion engine , electric motor (s) or

3871-512: The drivetrain vary, according to the type of vehicle. Some typical examples: The final drive is the last in the set of components which delivers torque to the drive wheels . In a road vehicle, it incorporates the differential . In a railway vehicle, it sometimes incorporates the reversing gear. Examples include the Self-Changing Gears RF 28 (used in many first-generation diesel multiple units of British Railways ) and RF 11 used in

3950-572: The early years of the war, they relied significantly on Lend-Lease vehicles, provided by the western allies. In 1943, they launched a further-developed version: the GAZ-67 . By contrast, the Axis powers ' closest equivalent to the jeep, the VW Kübelwagen , of which only some 50,000 were built, though being equipped with portal gear hubs, only had rear-wheel drive. Willys introduced the model CJ-2A in 1945,

4029-484: The first four-wheel driven automobile. The world's first four-wheel-drive car directly powered by an internal-combustion engine, and the first with a front-engine, four-wheel-drive layout , was the Dutch Spyker 60 H.P., Commissioned for the Paris to Madrid race of 1903, it was presented that year by brothers Jacobus and Hendrik-Jan Spijker of Amsterdam . The two-seat sports car featured permanent four-wheel drive and

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4108-521: The first full-production four-wheel-drive vehicle for sale in the general marketplace. Due to the ubiquitous World War II Jeep's success, its rugged utilitarianism set the pattern for many four-wheel-drive vehicles to come. Dodge also started production of the civilian 4WD Power Wagon trucks, for the 1946 model year. Both the Willys and the Dodge were developed directly from their WW II predecessors. Equally boxy to

4187-688: The forerunner of the designs that followed from other manufacturers. The automobile press at the time tested the traction of the Eagles and described it as far superior to the Subaru's and that it could beat many so-called off-road vehicles. Four Wheeler magazine concluded that the AMC Eagle was "The beginning of a new generation of cars." The Eagles were popular (particularly in the snowbelt ), had towing capacity, and came in several equipment levels including sport and luxury trims. Two additional models were added in 1981,

4266-400: The front and the rear axles. While a drivetrain that turns all wheels equally would normally fight the driver and cause handling problems, this is not a concern when wheels are slipping. Some designs use gearing to create a small rotational difference that hastens torque transfer. A typical Torsen II differential can deliver up to twice as much torque to the high-traction side before traction

4345-451: The front axle torque from a full-time mode with the 30:70 torque split of the center differential to the 0:100 torque split of the 2WD mode. In 1893, before the establishment of the modern automotive industry in Britain, English engineer Bramah Joseph Diplock patented a four-wheel drive system for a steam-powered traction engine , including four-wheel steering and three differentials , which

4424-404: The inclusion or exclusion of a low-range gear. On-demand AWD systems drive the secondary axle via an active or passive coupling device or "by an independently powered drive system". The standard notes that in some cases, the secondary drive system may also provide the primary vehicle propulsion. An example is a hybrid AWD vehicle where the primary axle is driven by an internal combustion engine and

4503-414: The military on a large scale, four-wheel drive and all-wheel-drive vehicles had not found their place. The World War II Jeep , originally developed by American Bantam , but mass-produced by Willys and Ford, became the best-known four-wheel-drive vehicle in the world during the war. The American Dodge WC series and Chevrolet G506 4x4 variants were also produced by the hundreds of thousands, as well as

4582-455: The more refined yet still off-road capable luxury 4WD Range Rover in the 1970s. With the acquisition of the "Jeep" name in 1950, Willys had cornered the brand. Its successor, Kaiser Jeep , introduced a revolutionary 4WD wagon called the Wagoneer in 1963. Not only was it technically innovative, with independent front suspension and the first automatic transmission coupled to 4WD, but also it

4661-512: The number of driven axles, meaning more gears to cut for all the differentials. Produced up to the war by a few specialized firms with limited capacity, from spring 1942, Ford, Dodge, and Chevrolet joined in fabricating these in a quantity more than a 100-fold greater than in 1939. Although Russia had their own jeep-like vehicle (the GAZ-64) up and running in 1940, a year earlier than the American jeep, in

4740-424: The off-road technology for an extra margin of safety and traction. The Eagle's thick viscous fluid center differential provided a quiet and smooth transfer of power that was directed proportionally to the axle with the greatest traction. This was a true full-time system operating only in four-wheel drive without undue wear on suspension or driveline components. No low range was used in the transfer case. This became

4819-408: The phase of the Moon at a particular point in time. An equation clock that used a differential for addition was made in 1720. In the 20th century, large assemblies of many differentials were used as analogue computers , calculating, for example, the direction in which a gun should be aimed. Chinese south-pointing chariots may also have been very early applications of differentials. The chariot had

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4898-542: The properly civilian GAZ-M-72, based on the rear-wheel drive GAZ-20 "Victory" and built from 1955 to 1958. Soviet civilian life did not allow the proliferation of civilian products such as the Jeep in North America, but through the 1960s, the technology of Soviet 4×4 vehicles stayed on par with British, German, and American models, even exceeding it in some aspects, and for military purposes just as actively developed, produced, and used. Until "go-anywhere" vehicles were needed for

4977-539: The rest by other licensed manufacturers. Only about 20% of the trucks built were four-wheel drives, but the 4x4s were more often on the front lines. About 11,500 of the Jeffery / Nash Quad trucks were built for similar use between 1913 and 1919. The Quad not only came with four-wheel-drive and four-wheel brakes, but also featured four-wheel steering. The Quad was one of the first successful four-wheel drive vehicles ever to be made, and its production continued for 15 years with

5056-489: The same axle driveshaft, they always have to spin at the same speed relative to each other. When going around a curve, this either forces one of the wheels to slip, if possible, to balance the apparent distance covered, or creates uncomfortable and mechanically stressful wheel hop. To prevent this, the wheels are allowed to turn at different speeds using a mechanical or hydraulic differential . This allows one driveshaft to independently drive two output shafts, axles that go from

5135-431: The schematic diagram on the right are: 1. Output shafts ( axles ) 2. Drive gear 3. Output gears 4. Planetary gears 5. Carrier 6. Input gear 7. Input shaft ( driveshaft ) An epicyclic differential uses epicyclic gearing to send certain proportions of torque to the front axle and the rear axle in an all-wheel drive vehicle. An advantage of the epicyclic design is that it is relatively compact width (when viewed along

5214-412: The secondary axle is driven by an electric motor. When the internal combustion engine is shut off, the secondary, electrically driven axle is the only driven axle. On-demand systems function primarily with only one powered axle until torque is required by the second axle. At that point, either a passive or active coupling sends torque to the secondary axle. In addition to the above primary classifications,

5293-440: The slipping wheel spins faster than the other wheels due to the lower traction at that wheel. Since a differential applies equal torque to each half-shaft, power is reduced at the other wheels, even if they have good traction. This problem can happen in both 2WD and 4WD vehicles, whenever a driven wheel is placed on a surface with little traction or raised off the ground. The simplistic design works acceptably well for 2WD vehicles. It

5372-473: The subcompact SX/4 and Kammback. A manual transmission and a front axle-disconnect feature were also made available for greater fuel economy. During 1981 and 1982, a unique convertible was added to the line. The Eagle's monocoque body was reinforced for the conversion and had a steel targa bar with a removable fiberglass roof section. The Eagle station wagon remained in production for one model year after Chrysler acquired AMC in 1987. Total AMC Eagle production

5451-615: The term is increasingly applied to mean "permanent multiple-wheel drive" on 2×2 , 4×4, 6×6, or 8×8 drive-train systems that include a differential between the front and rear drive shafts. This is often coupled with some sort of antislip technology, increasingly hydraulics-based, that allows differentials to spin at different speeds, but still be capable of transferring the torque from a wheel with poor traction to one with better. Typical AWD systems work well on all surfaces, but are not intended for more extreme off-road use. When used to describe AWD systems in light passenger vehicles, it refers to

5530-471: The two spur gears, and rotate in opposite directions. The remaining length of a given pinion meshes with the nearer spur gear on its axle. Each pinion connects the associated spur gear to the other spur gear (via the other pinion). As the carrier is rotated (by the input torque), the relationship between the speeds of the input (i.e. the carrier) and that of the output shafts is the same as other types of open differentials. Uses of spur-gear differentials include

5609-412: The various architectures and functions. The terms used by various manufacturers often reflect marketing rather than engineering considerations or significant technical differences between systems. SAE International 's standard J1952 recommends only the term "all-wheel drive" with additional subclassifications that cover all types of AWD/4WD/4x4 systems found on production vehicles. "Four-by-four" or "4×4"

5688-446: The vehicle and so requiring a long propeller shaft or drive shaft . The operating speed of the engine and wheels are also different and must be matched by the correct gear ratio . As the vehicle speed changes, the ideal engine speed must remain approximately constant for efficient operation and so this gearbox ratio must also be changed, either manually, automatically or by an automatic continuous variation . The precise components of

5767-416: The wheels at each end of a drive axle to rotate at different speeds while cornering. Other uses include clocks and analogue computers . Differentials can also provide a gear ratio between the input and output shafts (called the "axle ratio" or "diff ratio"). For example, many differentials in motor vehicles provide a gearing reduction by having fewer teeth on the pinion than the ring gear . Milestones in

5846-461: Was almost 200,000 vehicles. Drivetrain In contrast, the powertrain is considered to include both the engine and/or motor(s) as well as the drivetrain. The function of the drivetrain is to couple the engine that produces the power to the driving wheels that use this mechanical power to rotate the axle. This connection involves physically linking the two components, which may be at opposite ends of

5925-819: Was also the first car equipped with a six-cylinder engine, as well as four-wheel braking. Later used as a hill-climb racer, it is now an exhibit in the Louwman Museum (the former Nationaal Automobiel Museum) in the Hague , the Netherlands. Designs for four-wheel drive in America first came from the Twyford Motor Car Company . The Reynolds-Alberta Museum has a four-wheel-drive vehicle, named " Michigan ", from 1905 in unrestored storage. The first four-wheel-drive vehicles to go into mass production were built by (what became)

6004-588: Was developed, and 1,700 RF-40-X-4(USA) trucks were produced in 1938, and 292 TF-40-X-4(USA) in 1939. Starting in 1936, Japanese company Tokyu Kurogane Kogyo built roughly 4,700 four-wheel-drive roadsters, called the Kurogane Type 95 reconnaissance car, used by the Imperial Japanese Army from 1937 until 1944, during the Second Sino-Japanese War . Three different bodystyles were manufactured –

6083-460: Was equipped and finished as a regular passenger automobile. In effect, it was the ancestor of the modern SUV . The luxury AMC or Buick V8 -powered Super Wagoneer produced from 1966 to 1969 raised the bar even higher. Jensen applied the Formula Ferguson (FF) full-time all-wheel-drive system to 318 units of their Jensen FF built from 1966 to 1971, marking the first time 4WD was used in

6162-442: Was relatively unchanged during its production through 1991, even after Chrysler 's buyout of AMC. Subaru introduced the category-expanding Leone in 1972, an inexpensive compact station wagon with a light-duty, part-time four-wheel-drive system that could not be engaged on dry pavement. In September, AMC introduced Quadra Trac full-time AWD for the 1973 model year Jeep Cherokee and Wagoneer. Due to full-time AWD, which relieved

6241-425: Was subsequently built. The development also incorporated Bramah's Pedrail wheel system in what was one of the first four-wheel drive automobiles to display an intentional ability to travel on challenging road surfaces. It stemmed from Bramagh's previous idea of developing an engine that would reduce the amount of damage to public roads. Ferdinand Porsche designed and built a four-wheel-driven electric vehicle for

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