Four-wheel drive 444649 225823135 2008-07-15T15:53:08Z CZmarlin 1606992 /* History */ rm - the added information is not even in the [[International Harvester Scout]] page {{Cleanup|date=March 2008}} {{otheruses4|the class of vehicles|other uses|Four by four/Four-wheel drive (disambiguation)}} [[Image:Jeep Wrangler TJ.jpg|thumb|right|The [[Jeep Wrangler]] is a 4WD vehicle with a transfer case to select low range or high range 4WD.]] '''Four-wheel drive''', '''4WD''', or '''4x4''' ("four by four") is a four-wheeled [[vehicle]] with a [[Powertrain|drivetrain]] that allows all four [[wheel]]s to receive torque from the [[engine]] simultaneously. In the [[United States]], these cars are often, but not always, included in the broader [[sport utility vehicle]] category. While many people associate the term with [[off-road vehicle]]s, powering all four wheels provides better control in normal road cars on many surfaces, and is an important part of [[rallying|rally racing]]. The first figure is the number of wheels. The second is the number of powered wheels. With a 4x2, engine power is transmitted to only two wheels, usually the rear.<ref>http://4wheeldrive.about.com/cs/offroadingtips/a/aa021401a.htm</ref> The term ''four-wheel drive'' describes [[truck]]-like vehicles that require the driver to manually switch between two-wheel drive mode for streets and four-wheel drive mode for low [[traction (engineering)|traction]] conditions such as ice, mud, snow, slippery surfaces, or loose gravel. ''All-wheel drive'' (AWD) is often used to describe a "full time" 4WD that may be used on dry pavement without destroying the drivetrain, although the term may be abused when marketing a vehicle. AWD can be used on dry pavement because it employs a center [[Differential (mechanical device)|differential]], which allows each tire to rotate at a different speed. ("Full-Time" 4WD can be disengaged and the center differential can be locked, essentially turning it into regular 4WD. On the other hand, AWD cannot be disengaged and the center differential cannot be locked.<ref>{{cite web | url=http://auto.howstuffworks.com/four-wheel-drive.htm | title=How Four-Wheel Drive Works}}</ref><ref>{{cite web | url=http://www.4x4abc.com/4WD101/def_turnpart.html | title=part time 4WD can not be used on pavement}}</ref>) This eliminates driveline binding, wheel hop, and other driveline issues associated with the use of 4WD on dry pavement. With vehicles with more than four wheels, AWD means all wheels drive the vehicle, to varying degrees of engagement, while 4WD means only four of the wheels drive the vehicle continuously. Identical drivetrain systems are commonly marketed under different names for [[upmarket]] and [[downmarket]] branding and, conversely, different drivetrain systems are commonly marketed under the same name for brand uniformity. [[Audi]]'s [[quattro (four wheel drive system)|quattro]], [[DaimlerChrysler]]'s [[4Matic]] used on [[Mercedes-Benz]] products, [[BMW]] with the [[BMW xDrive|xDrive]], and [[Volkswagen]]'s [[4motion]], for example, can mean either an automatically-engaging "on-demand" system with a [[Haldex Traction]] [[clutch]], or a continuously-operating permanent 4WD system with a [[Torsen]] (torque-sensing) [[differential (mechanics)|differential]]. There is often confusion as to the difference between 4x4s and SUVs. This leads to criticisms of 4x4 vehicles in the media that should actually be directed at SUVs (see [[SUV Criticism]]). ==Design== [[Image:En 4wd english.png|thumb|left|Sketch of 4WD (AWD)]] ===Differentials=== [[Image:Lamborghini Murciélago Roadster 2005.JPG|thumb|right|The [[Lamborghini Murciélago]] is a 4WD/AWD that powers the front via a [[viscous coupling unit]] if the rear slips.]] [[Image:Hmmwv-036.jpg|thumb|right|The [[HMMWV]] is a 4WD/AWD that powers all wheels evenly (continuously) via a manually lockable center differential, with [[Torsen]] differentials for both front and rear.]] [[Image:Car rally.jpg|thumb|right|A [[Subaru Impreza]] [[rally car]] uses AWD for traction on loose dirt.]] When powering two wheels simultaneously the wheels must be allowed to rotate at different speeds as the vehicle goes around curves. The problem is even more complicated when driving all four wheels. A design that fails to account for this will cause the vehicle to handle poorly on turns, fighting the driver as the tires slip and skid from the mismatched speeds. A [[differential (mechanics)|differential]] allows one input shaft to drive two output shafts with different speeds. The differential distributes [[torque]] (angular force) evenly, while distributing [[angular velocity]] (turning speed) such that the average for the two output shafts is equal to that of the input shaft. Each powered axle requires a differential to distribute power between the left and the right sides. When all four wheels are driven, a third differential can be used to distribute power between the front and the rear axles. Such a design handles well. It distributes power evenly and smoothly, and makes 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, the slipping wheel will spin faster than the other wheels due to the lower traction at that wheel. Although the amount of torque applied to each wheel will be identical, the amount of traction at each driven wheel will be limited to that of the wheel with the least traction (all four wheels on ice in this case). 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 is much less acceptable for 4WD vehicles because 4WD vehicles have twice as many wheels to lose traction, increasing the likelyhood that it will happen. 4WD vehicles may also be more likely to be driven on surfaces with reduced traction. ===Limiting slippage=== [[Traction control]] was invented to solve this problem for 2WD vehicles. When one wheel spins out of control the [[brake]] is automatically applied to that wheel. By preventing one wheel from spinning freely power is divided between the pavement for the non-slipping wheel and the brake for the slipping wheel. This is an effective solution, although it causes additional brake wear and may cause a sudden jolt that affects handling. By extending traction control to act on all four wheels the simple three-differential 4WD design will see limited wheel spin. This design is commonly seen on luxury [[crossover SUV]]s. [[Locking differential]]s temporarily lock 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 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. The two most common factory-installed locking differentials use either a computer-controlled [[multi-plate clutch]] or [[viscous coupling unit]] to join the shafts, while other differentials more commonly used on off-road vehicles generally use manually operated locking devices. In the multi-plate clutch the vehicle's computer senses slippage and locks the shafts, causing a small jolt when it activates, which can disturb the driver or cause additional traction loss. In the viscous coupling differentials the [[shear stress]] of high shaft speed differences causes a [[dilatant]] fluid in the differential to become solid, linking the two shafts. This design suffers from fluid degradation with age and from [[exponential]] locking behavior. Some designs use gearing to create a small rotational difference which hastens torque transfer. A third approach to limiting slippage is the Torsen differential. A Torsen differential allows the output shafts to receive different amounts of torque. This design does not provide for traction when one wheel is spinning freely, where there is no torque. It provides excellent handling in less extreme situations. A typical Torsen II differential can deliver up to twice as much torque to the high traction side before traction is exceeded at the lower tractive side. Finally, many lower-cost vehicles entirely eliminate the center differential. These vehicles behave as 2WD vehicles under normal conditions. When the drive wheels begin to slip, one of the locking mechanisms discussed above will join the front and rear axles. Such systems distribute power unevenly under normal conditions and thus do not help prevent the loss of traction, instead only enabling recovery once traction is lost. Most minivan 4WD/AWD systems are of this type, usually with the front wheels powered during normal driving conditions and the rear wheels served via a viscous coupling unit. Such systems may be described as having a 95/5 or 90/10 power split. ==History== [[Image:1903-Spyker-60-HP-1920x1440.jpg|thumb|The 1903 Spyker 60 H.P. 4WD]] [[Image:Center differential Jeep Grand Cherokee AWD.jpg|thumb|Center transfer case sending power from the transmission to two output shafts: to the rear axle (visible on the right) as well as to the front axle (on the left side).]] [[Image:Transfer lever 4wd gnangarra.jpg|thumb|Selection lever]] The true inventor of four-wheel drive is not really known; the history of such was not well recorded. In 1893, before the establishment of a modern automotive industry in Britain, [[England|English]] engineer Joeseph Bramah Diplock patented a four wheel drive system for a [[traction engine]], including four-wheel steering and three differentials, which was subsequently built. The development also incorporated Bramagh'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 the ''k. u. k. Hofwagenfabrik Ludwig Lohner & Co.'' at Vienna in 1899, presented to the public during the 1900 World Exhibition at Paris. The vehicle was powered by an electric [[hub motor]] at each wheel, a design later used by [[NASA]] in the [[Lunar rover]]. Although clumsily heavy, the vehicle proved a powerful sprinter and record-breaker in the hands of its owner E.W. Hart. Due to its unusual status the so-called ''Lohner-Porsche'' is not widely credited as the first four-wheel driven automobile. The first four-wheel drive car, as well as hill-climb racer, with internal combustion engine, the ''[[Spyker]] 60 H.P.'', was presented in 1903 by Dutch brothers Jacobus and Hendrik-Jan Spijker of [[Amsterdam]]. The two-seat sports car, which was also the first ever car equipped with a six-cylinder engine, is now an exhibit in the Louwman Collection (the former ''Nationaal Automobiel Museum'') at [[Geertruidenberg|Raamsdonksveer]] in The Netherlands. Designs for four-wheel drive in the U.S., came from the Twyford Company of [[Brookville, Pennsylvania]] in 1905, six were made there around 1906; one still exists and is displayed annually.<ref>[http://www.novak-adapt.com/knowledge/model_18.htm Novak Conversions&nbsp;&mdash; The Dana Spicer Model 18 Transfer Case<!-- Bot generated title -->]</ref> The second U.S. four-wheel drive vehicle was built in 1908 by (what became) the [[Four Wheel Drive]] Auto Company (FWD) of [[Wisconsin]]. FWD would later produce over 20,000 of its four-wheel drive Model B trucks for the [[United Kingdom of Great Britain and Ireland|British]] and [[United States|American]] armies during [[World War I]]. Thousands of the [[Thomas B. Jeffery Company|Jeffery Quad]] (1913-1919) were similarly used. The [[Reynolds-Alberta Museum]] has a four-wheel drive "[[List of cars#L-N|Michigan]]" car from about 1905 in unrestored storage. [[Daimler-Benz]] also has a history in four-wheel drive. In 1907 the [[Daimler Motoren Gesellschaft]] had built a four-wheel driven vehicle called ''Dernburg-Wagen'', also equipped with [[steering#four-wheel steering|four-wheel steering]], that was used by German colonial civil servant, Bernhard Dernburg, in [[Namibia]]. Mercedes and BMW, in 1926, introduced a rather sophisticated four-wheel drive, the G1, the G4 and G4 following. The 1937 Mercedes-Benz G5 and BMW 325 4x4 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 a four-wheel drive passenger vehicle. The modern G-series/Wolf such as the [[G-Class|G500]] and [[G-Class#Model|G55]] [[Mercedes-AMG|AMG]] still feature some of the attributes, with the exception of fully independent suspension since it hinders suspension articulation. The [[Unimog]] is another Mercedes truck. It was not until "go-anywhere" vehicles were needed for the military that four-wheel drive found its place. The [[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 [[World War II]]. [[Willys]] (since 1950 owner of the Jeep name) introduced the [[Jeep CJ#CJ-2A|CJ-2A]] in 1945 as the first full-production four-wheel drive passenger vehicle. Possibly beaten by the 1941 [[GAZ-61]]. The [[Land Rover]] appeared at the Amsterdam Motor Show in 1948, originally conceived as a stop-gap product for the struggling Rover car company, and despite chronic under-investment succeeded far better than the passenger cars. Land Rover developed a luxury 4WD with the [[Range Rover]] in the 1970s, which, unlike some offerings from other manufacturers, was capable of serious off-road use. The inspiration was a [[Willys MB]] that was frequently run off-road on the farm belonging to chief engineer [[Maurice Wilks]], and was felt that it needed some refinement. [[Kaiser Jeep]] introduced a 4WD wagon called the [[Jeep Wagoneer|Wagoneer]] in 1963. It was revolutionary at the time, not only because of its technical innovations such as an [[independent front suspension]] and the first [[automatic transmission]] with 4WD, but also because it was equipped and finished as a regular passenger automobile. The Super Wagoneer (1966 to 1969) was powered by [[Rambler (automobile)|Rambler]] or [[Buick]] [[V8 engine|V8s]]. Its high level of equipment made it the first "luxury" SUV. [[American Motors]] (AMC) acquired Kaiser's Jeep Division in 1970 and quickly upgraded and expanded the entire line of serious off-road built 4WD vehicles. The top range full-size Wagoneer Limited continued to compete with traditional [[Luxury vehicles|luxury cars]]. It was relatively unchanged during its production through 1991, even after [[Chrysler|Chrysler's]] buyout of AMC. [[Jensen Motors|Jensen]] applied the ''Formula [[Ferguson Research Ltd.|Ferguson]]'' 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 a production GT sports car.<ref>[http://auto.howstuffworks.com/1966-1971-jensen-ff.htm "1966-1971 Jensen FF" by the Auto Editors of Consumer Guide, not dated]. Retrieved on [[March 16]] [[2008]].</ref> [[Subaru]] introduced the mass-produced [[Subaru Leone|Leone]] in 1972 featuring a part-time four-wheel drive systems that could not be engaged on dry pavement. The American Motors Company introduced a full time AWD vehicle the same year as the Subaru in the Jeep Cherokee and Wagoneer with Quadra Trac (1973 model year first models sold in Sept 1972)<ref>[http://auto.howstuffworks.com/1963-1992-jeep-wagoneer-and-grand-wagoneer4.htm Howstuffworks "1967-1977 Jeep Wagoneer"<!-- Bot generated title -->]</ref>. It dominated all other makes in FIA rally competition, due to the performance of the full time AWD, which did not require the driver to get out of the vehicle to [[Locking hubs|lock hubs]] or manually select between 2WD and 4WD modes in the car like other American 4-wheel drive vehicles of the period. Drivers Gene Henderson and Ken Pogue won the FIA championship with a quadratrac equipped Jeep in 1972 <ref>[http://en.wikipedia.org/wiki/Press-on-Regardless_Rally]</ref> [[Image:1987 AMC Eagle wagon burgundy-woodgrain NJ.jpg|thumb|1987 AMC Eagle, the wagon was the most popular model]] [[Image:1981 AMC Eagle convertible beige NJ.jpg|thumb|1981 AMC Eagle AWD convertible]] American Motors introduced the innovative [[AMC Eagle|Eagle]] for the 1980 model year.<ref>[http://findarticles.com/p/articles/mi_m3012/is_2_181/ai_70935228 Sherman, Don. "All-Wheel-Drive Revisited: AMC's 1980 Eagle pioneered the cross-over SUV." Automotive Industries, February 2001], retrieved on [[March 16]] [[2008]].</ref> This was the world's first complete line ([[sedan]], [[coupe]], and [[station wagon]]) of 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 the off-road technology for an extra margin of safety and traction.<ref>[http://www.nytimes.com/2008/03/09/automobiles/collectibles/09EAGLE.html?_r=1&oref=slogin Sass, Rob, "A Breed of 4-by-4 Hatched on the Fly" The New York Times, March 9, 2008], retrieved on [[March 16]] [[2008]].</ref> The Eagle's thick [[viscous]] fluid center differential provided 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. There was no low range in the transfer case. This became 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."''<ref>[http://amxfiles.com/amc/eagle.html 1980-88 AMC Eagle 4wd (Autoweek)<!-- Bot generated title -->]</ref> 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, the sub-compact 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 top|targa bar]] with a removable fiberglass roof section. The Eagle station wagon remained in production for one year after Chrysler Corporation acquired AMC in 1987. [[Audi]] also introduced a permanently all-wheel driven road-going car, the [[Audi Quattro]], in 1980. Audi's chassis engineer, Jorg Bensinger, had noticed in winter tests in Scandinavia that a vehicle used by the German Army, the [[Volkswagen]] [[Iltis]], could beat any high performance Audi. He proposed developing a four-wheel drive car, soon used for ''[[rallying]]'' to improve Audi's conservative image, the resulting rally bred [[Audi Quattro]] was a famous and historically significant Rally car. This feature was also extended to Audi's production cars and is still available today. In 1987, [[Toyota]] also developed a car built for competition in rally campaigns.<ref>[http://www.alltrac.net/FAQ.html#origin Celica All Trac and Gt-Four FAQ<!-- Bot generated title -->]</ref> A limited number of road-going [[Fédération Internationale de l'Automobile|FIA]] [[Homologation]] Special Vehicle Celica GT-Fours (otherwise known as [[Toyota Celica]] Turbo All-Trac in some markets) were produced. The All-Trac system was later available on serial production [[Toyota Camry]], [[Toyota Corolla]], and [[Toyota Previa]] models. Some of the earliest [[mid-engined]] four-wheel drive cars were the various road-legal rally cars made for [[Group B]] homologation, such as the [[Ford RS200]] made from 1984-86. In 1989, niche maker [[Panther Westwinds]] created a [[mid-engined]] four-wheel drive, the [[Panther Solo|Panther Solo 2]]. Today, sophisticated all-wheel drive systems are found in many passenger vehicles and most exotic [[sports car]]s and [[supercar]]s. ==4WD in road racing== [[Bugatti]] created a total of three four-wheel drive racers, the [[Bugatti Type 53|Type 53]], in 1932, but the cars were legendary for having poor handling. [[Ferguson Research Ltd.]] built the front-engine P99 [[Formula One]] car that actually won a non-WC race with [[Stirling Moss]] in 1961. In 1969, [[Team Lotus]] raced cars in F1, and the [[Indy 500]], that had both turbine engines and 4WD, as well as the 4WD-Lotus 63 that had the standard [[Cosworth]] engine. [[Matra]] also raced a similar MS84, and [[McLaren]] entered their [[McLaren M9A|M9A]] in the [[1969 British Grand Prix|British Grand Prix]], while engine manufacturers Cosworth produced their own version which was tested but never raced. All these F1 cars were considered inferior to their RWD counterparts, as the advent of aerodynamic downforce meant that adequate traction could be obtained in a lighter and more mechanically efficient manner, and the idea was discontinued, even though Lotus tried repeatedly. ==Terminology== Although in the strictest sense, the term "four-wheel drive" refers to a capability that a vehicle may have, it is also used to denote the entire vehicle itself. In [[Australia]], vehicles without significant off-road capabilities are often referred to as All-Wheel Drives (AWD) or SUVs, while those with off-road capabilities are referred to as "four-wheel drives". This term is sometimes also used in [[North America]], somewhat interchangeably for [[SUV]]s and pickup trucks and is sometimes erroneously applied to two-wheel-drive variants of these vehicles. The term '''4x4''' (read either ''four by four'' or ''four times four'') was coined in the [[1950s]] to designate a vehicle, primarily a truck, which was equipped with a [[transfer case]] to drive the front wheels in addition to the rear wheels ([[rear-wheel drive]] was the norm) and a four-speed [[Manual transmission |transmission]] (three speeds were the norm). Usually the [[Gear stick|shifter]] was mounted on the [[floorpan]] (column shifters were the norm). Today, as the "norms" have shifted, the term has evolved with the times and may be used to denote the ''total'' number of wheels on a vehicle and the number of ''driven'' wheels; it is often applied to vehicles equipped with either full-time or part-time four-wheel-drive. The term '''4x4''' is common in North America and is generally used when marketing a new or used vehicle, and is sometimes applied as badging on a vehicle equipped with four-wheel drive. Similarly, a '''4x2''' would be appropriate for most two-wheel-drive vehicles, and is often used to describe them as a two-wheel drive. In Australia the term is often used to describe a [[ute]] that sits very high on its suspension. This is to avoid the confusion that the vehicle might be a 4x4 because it appears to be otherwise suited to off-road applications. Large American trucks with dual tires on the rear axles and two driven axles are officially designated as 4x4s, despite having six driven wheels, because the "dual" wheels behave as a single wheel for traction purposes and are not individually powered. True '''[[6x6]]''' vehicles with three powered axles such as the famous "[[deuce and a half]]" truck used by the [[U.S. Army]] has three axles (two rear, one front), all of them driven. This vehicle is a true '''6x6''', as is the [[Pinzgauer High Mobility All-Terrain Vehicle|Pinzgauer]], which is popular with defense forces around the globe. Another related term is ''[[4-wheeler]]'' (or ''four-wheeler''). This generally refers to [[all-terrain vehicle]]s with four wheels and does not indicate the number of driven wheels; a "four wheeler" may have two or four-wheel drive. (In [[CB slang]], truckers refer to any two-axled vehicle as a "four-wheeler," sometimes in a derogatory sense, as distinguished from an "eighteen-wheeler" or [[semi-truck|tractor/trailer]].) ==Unusual four-wheel drive systems== Prompted by a perceived need for a simple, inexpensive all-terrain vehicle for oil exploration in North Africa, the [[France|French]] motor manufacturer [[Citroën]] developed the [[Citroën 2CV|2CV]] Sahara. Unlike other 4x4 vehicles which use a conventional [[transfer case]] to drive the front and rear axle, the Sahara had two engines, each independently driving a separate axle, with the rear engine facing backwards. The two throttles, clutches and gear change mechanisms could be linked, so both {{Convert|12|hp|kW|0|abbr=on}} {{Auto cc-cu in|425|0}} engines could run together, or they could be split and the car driven solely by either engine. Combined with twin fuel tanks and twin batteries (which could be set up to run either or both engines), the redundancy of two separate drive trains meant that they could make it back to civilization even after major mechanical failures. Only around 700 of these cars were built, and only 27 are known to exist today.<ref>[http://www.ultimatecarpage.com/frame.php?file=car.php&carnum=1870 Citroën 2CV Sahara - Ultimatecarpage.com - Images, Specifications and Information<!-- Bot generated title -->]</ref> Enthusiasts have built their own "new" Saharas, by rebuilding a 2CV and fitting the modified engine, gearbox and axle onto a new, strengthened chassis. [[British Motor Corporation|BMC]] experimented with a twin-engine [[Mini Moke]] (dubbed the "Twini Moke") in the mid-1960s, but never put it into production. This made advantage of the [[Austin Mini|Mini's]] 'power pack' layout, with a transverse engine and the [[gearbox]] in the engine [[sump]]. Simply by fitting a second engine/gearbox unit across the rear, a rudimentary 4x4 system could be produced. Early prototypes had separate gear levers and clutch systems for each engine. Later versions sent for evaluation by the [[British Army]] had more user-friendly linked systems. [[Suzuki Motors]] introduced the [[Suzuki Escudo]] Pikes Peak Edition in 1996. The engine is a twin-turbocharged 2.0&nbsp;L V6, mated to a sequential 6-speed manual transmission. [[Nissan Motors]] has developed a system called [[Nissan e4WD|E4WD]], wherein the rear wheels, in a car that is normally front-wheel drive, are driven by electric motors. This system was introduced in some variants of the [[Nissan Cube]] and [[Nissan Tiida|Tiida]]. Chrysler's [[Jeep]] Division debuted the twin engine, {{Convert|670|hp|kW|0|abbr=on}} [[Jeep Hurricane]] concept at the 2005 [[North American International Auto Show]] in [[Detroit]]. This vehicle has a unique "crab crawl" capability, which allows it to rotate 360° in place. It also has dual [[Chrysler Hemi engine|Hemi]] V8s. Some [[hybrid electric vehicle|hybrid vehicles]] such as the [[Lexus]] [[Lexus RX400h|RX400h]] provide power to an AWD system through a pair of electric motors, one to the front wheels and one to the rear. In the case of the AWD model version of the Lexus RX400h (and its Toyota-branded counterpart, the [[Toyota Highlander|Highlander]] hybrid), the front wheels can also receive drive power directly from the vehicle's gasoline engine as well as via the electric motors, whereas the rear wheels derive power only from the second electric motor. Transfer of power is managed automatically by internal electronics based on traction conditions and need, making this an all-wheel drive system. ==4WD and AWD systems by design type== [[Image:Mercedes M-Class at a carshow in Chicago 2005.jpg|thumb|right|The [[Mercedes-Benz M-Class]] is a 4WD that powers all wheels evenly (continuously) via an open [[differential (mechanics)|differential]], and uses [[traction control]] to recover from wheel spin]] [[Image:04-05 Honda CR-V.jpg|thumb|right|Honda CR-V uses a dual pump differential and lockup torque converter]] ===Center differential with mechanical lock, or other torque transfer features=== * [[Alfa Romeo 164]] Q4 (central viscous coupling, epicyclic unit and Torsen rear differential) * [[Alfa Romeo 155]] Q4 (central epicyclic unit, Ferguson viscous coupling and Torsen rear differential) * [[Audi]] - [[Audi Quattro|Quattro]] Coupé, 4000, 5000 (locking center and rear differentials) * [[Audi Q7]] -double pinion 50/50 with lockup clutch pack * Ford - Escort (RS 2000 16v 4x4 models and RS Cosworth), Sierra Cosworth, Sierra and Granada 4x4 models * [[GL-Class|Mercedes GL-Class]] * H1 & [[HMMWV]] NVG 242HD AMG open center differential, locked center differential, Neutral, low range locked. Also [[Torsen differential|Torsen1 differential]] at the front and rear axle, The H1 moved to Torsen2 when ABS was added. The H1 Alpha had optional locking differentials in place of torsens * Hummer H2, H3 40/60 planetary with lock * Jeep Grand Cherokee, Commander ([[Quadra-Drive]] 2 version only for both vehicles) * Jeep Liberty, [[Jeep Cherokee]], [[Dodge Durango]] ([[Select-Trac]])- NV 242 transfer case- rear drive, open center differential, locked center differential, Neutral, low range * [[Jeep SJ|Full size Jeeps]] with Borg Warner QuadraTrac: limited slip center differential, 50/50 locked center differential. Low range could be used in locked or unlocked mode, allowing for use of low range on pavement. * [[Land Rover]] Defender (and [[Land Rover Series|Series III]] [[Rover V8 engine|V8 models]]) * [[Land Rover]]/[[Land Rover Discovery]]/LR3 * [[Lada Niva]] - full-time 4WD using open center diff with manual lock * Lexus LX470 -open with lock * Lexus RX300 -[[viscous coupling unit|viscous coupling]] across the otherwise open center differential. * Mercedes-Benz Unimog (locking center and rear with up to 10 low range gears). * [[Mercedes-Benz G-Class]] (locking center and lockers on both front- and rearaxle) * Mitsubishi Pajero (also known as Montero or Shogun) * Nissan Pathfinder/Armada (All-Mode) multi clutch based with locking center differential * Porsche Cayenne ([[Porsche Traction Management]]) 38/62 planetary with lockup clutch pack * [[Range Rover]] * Suzuki Grand Vitara -full-time 4WD using limited-slip center differential, off-road 4WD with selectable center differential lock and low range transfer case, [[traction control]] and [[electronic stability control]] * [[Subaru]] Basic manual transmissions have a 50/50 center differential with viscous clutch, performance models have a planetary differential with computer regulated lockup. Automatic transmission models have ~45/55 planetary with computer controlled lock up * Toyota Sequoia ([[Multi-mode]]) * [[Toyota Land Cruiser]] * [[Volkswagen Touareg]] -double pinion 50/50 with lockup clutch pack ===Torsen center differential=== * [[Alfa Romeo]]s: [[Alfa Romeo 156|156 Crosswagon]], [[Alfa Romeo 159|159]], [[Alfa Romeo Brera|Brera]], [[Alfa Romeo Brera|Spider]] Q4 ([[Torsen]] T-3) * [[Audi]]s with ([[quattro (four wheel drive system)|quattro]]) - [[Audi 80|80 & 90]], [[Audi 100|100 & 200]], [[Audi A4|A4]], [[Audi S4|S4]], [[Audi RS4|RS4]], [[Audi A5|A5 & S5]], [[Audi A6|A6]], [[Audi S6|S6]], [[Audi RS6|RS6]], [[Audi A8|A8]], [[Audi S8|S8]], [[Audi R8|R8]], [[Audi Q7|Q7]] (center) - various iterations of Torsen, including the latest T-3 * [[Bentley Continental GT]], [[Bentley Continental Flying Spur (2005)]] Torsen T-1 * [[Chevrolet Trailblazer]] SS (center)(limited slip rear) Torsen T-3 * [[Lexus GX]]470, [[Toyota Landcruiser]] 120/Prado (center) (with limited slip rear) Torsen T-3 with lock * [[Toyota FJ Cruiser]] (center) (only manual models) (also locking rear) Torsen T-3 with lock * [[Toyota Hilux]] Surf or 4Runner (center) (also locking rear) Torsen T-3 with lock * [[Toyota Landcruiser]] 200/2008/V8 Torsen T-3 with lock * [[Volkswagen Passat]] 4motion Torsen T-2 (not latest model with transverse engine) * [[Volkswagen Phaeton]] (center) Torsen T-2 ===Non-locking center differential=== * Cadillac Escalade, STS AWD, SRX AWD (The first two generations had a viscous clutch on the center differential) * Chrysler 300C AWD * Dodge Magnum, Charger AWD * GMC Yukon Denali, XL Denali, Sierra Denali * Mercedes [[4MATIC]] cars, R class, and ML class (note some MLs had low range) The above systems function by selectively using the traction control system (via ABS) to brake a slipping wheel. ===Multiple-clutch systems=== * [[Acura]] RL, RDX ([[SH-AWD]]) Right and left axle shaft * Acura MDX [[SH-AWD]] & VTM4 * [[Honda]] Ridgeline * Honda Pilot * Mitsubishi GTO MR/3000GT VR-4 * [[Mitsubishi Lancer Evolution]] Series * [[Nissan GT-R]] (ATTESA E-TS) * Nissan Skyline GT-R (ATTESA E-TS and ATTESSA E-TS-PRO) front axle coupling, rear differential locking * Nissan Skyline GTS4 ([[ATTESA E-TS]]) * Nissan A31 Cefiro SE4 ([[ATTESA E-TS]]) * [[Porsche 959]] PSK front axle coupling, rear differential locking * [[Saab 9-3]], [[Saab 9-4X]] ([[Saab XWD]]). ===Clutch pack coupling=== *[[Subaru]] low powered automatic transmission models *[[Subaru]] [[Legacy]], [[Outback]], [[Impreza]], [[Forester]], [[Tribeca]] automatic transmission models: mechanical front drive, clutch coupled rear axle. * [[Audi A3]] quattro, [[Audi TT]] quattro (with [[Haldex Traction]]) * [[BMW]]: 3series, 5series, X3, X5 (the initial X5's had a 38/62 planetary center differential) * [[Chevrolet Equinox]] (GMPCA) * [[Chrysler Pacifica]] ([[BorgWarner]] ITM3e) (on 2007 model) * [[Dodge Nitro]] ([[Quadra-Trac]] 1) * [[Dodge Caliber]] * [[Ford]]: Escape, Freestyle, Edge, Fusion, Five Hundred (Freestyle, FiveHundred [[Haldex Traction]] based)(Escape [[Control Trac II]], based) * [[Honda CR-V]], HR-V, Element * [[Infiniti]]: G35x, M35x * [[Jeep Compass]] ([[Freedom Drive]]) * [[Jeep]]: Grand Cherokee and SRT8 NVG 249, 247 * [[Land Rover]]: LR2 (also [[Haldex Traction]])<ref>according to Car and Driver Vol52No8 Feb 07 page 110</ref> * [[Lamborgini]]: AWD variants VT series (viscous traction) * [[Lincoln (automobile)|Lincoln]]: MKS, MKZ * [[Mazdaspeed6]] (a power takeoff unit linked to clutch pack with torque sensitive rear differential.) * [[Mazda]]: Tribute, CX-7, CX-9 (tribute [[Control Trac II]], based) * [[Mercury (automobile)|Mercury]]: Milan, Montego, Mariner (Montego [[Haldex Traction]] based) * [[Mitsubishi Outlander]] (current generation) * [[Nissan Murano]] automatic with manual lockup switch * [[Porsche 911]] AWD variants (a version of [[BorgWarner]] ITM3e)&nbsp;&mdash; excluding the 964-series Porsche 911 Carrera 4 31/69 planetary center differential * [[Pontiac Torrent]] (GMPCA) * [[Suzuki]]: SX4, XL7, Aerio * [[Toyota RAV4]] (latest model, not older generations) * [[Volvo]]: S40, S60, S80, V50, V70, XC70, XC90 (all [[Haldex Traction]]-based) * [[Volkswagen]] [[4motion]] cars with transverse mounted engine: [[Volkswagen Golf|VW Golf]] ([[Haldex Traction]]) Note the above all function like 2WD when clutch pack not engaged, and like 4WD highrange in a part time 4WD system when the clutch is engaged (usually by computer although some allow manual control). Some in this category have varying degrees of control in the torque distribution between front and rear via allowing some of the clutches in a clutch pack to engage and slip varying amounts. An example of a system like this is the BorgWarner [[i-Trac]](TM) system. Note: the [[Haldex Traction]] based car list was created from the list on Haldex Traction corporate web site: [http://www.haldex-traction.com/awdclub/carmodels.htm | Haldex Cars]. Interestingly, a version of the [[BorgWarner]] ITM3e system is used on 2006 and up Porsche 911TT's. These Borg Warner systems were the forerunner of the popular [[Volkswagen Group]] [[Direct-Shift Gearbox]] (DSG) gearbox. ===Off-road drive=== These are vehicles with no center differential, also known as selectable 4WD. Off-road drive systems may not be driven in 4WD mode on dry pavement, as damage to the transfer case will occur. * Chevrolet Trailblazer and GMC Envoy * Chevrolet Tahoe Z71, Suburban Z71, Silverado Z71, Colorado Z71, s-10 series ZR2 * Chevrolet Tracker * Dodge Power Wagon (a Ram version with front and rear differential locks) * Dodge Ram, Dakota * Dodge Nitro (Quadra-Trac 2) * Ford F series FX4, Explorer, Expedition, Sport Trac (all control Trac 1) * Ford Ranger (Torsen rear differential) * Geo Tracker * GMC Yukon Z71, Sierra Z71 * Infiniti QX56 (All-mode 4WD) Auto-engages 4WD with slip * Isuzu i-series * Jeep Cherokee (Quadra-Trac 2) * Jeep Cherokee, Jeep Wrangler, Jeep Comanche, Jeep Grand Cherokee (ZJ), Jeep Liberty (Command-Trac) * Jeep Wrangler (Rubicon has a locking front as well as rear) * [[Land Rover Series]] (except [[Rover V8 engine|V8]] models) * Lincoln Navigator (slip sensing can shift automatically into 4-high) * Lincoln Mark LT * Mazda B-series * Mitsubishi Raider * Nissan Patrol * Nissan Armada, Pathfinder (All-mode 4WD) Auto-engages 4WD with slip * Nissan Titan, Xterra, Frontier (rear locker an option) * Subaru [[Loyale]], GL/DL, [[Brat]] Front/4wd/4wd lo, [[Justy]] * Suzuki Sidekick * Toyota Tacoma (rear locking differential optional) * Toyota Tundra TRD * Toyota FJ Cruiser (automatic transmission models) == Common 4WD clearance dimensions == {| class="wikitable" |- ! Vehicle Name ! Ground Clearance (in) ! Approach Angle ! Departure Angle ! Ramp Over Angle |- |Land Rover Defender 90 | 10 | 47° | 47° | 33° |- |Land Rover Defender 110 |12 |49° |35° |30.3° |- |Hummer H1 |16 |72° |37.5 |29 |- |Hummer H2 |10.8 |40.8° |40° |27.5° |- |Hummer H3 |8.8 |39.4° |35.5° |25.0° |- |Mitsubishi Pajero |8.9 |36.6° |25° |22.5° |- |Mitsubishi Pajero R |8.8 |36.7° |34.8° |25.2° |- |- |Jeep Wrangler Rubicon |10.2 |44.3° |40.4° |25.3° |- |Jeep Wrangler Rubicon UL |10.1 |44.4° |40.5° |20.8° |- |Jeep Liberty |9.4 |37.2° |31.5° |21.8° |- |Jeep Grand Cherokee |9.1 |34.1° |27° |20° |- |Jeep Commander |8.5 |34.6° |27.2° |21.2° |- |Nissan Xterra |9.5 |33.2° |29.4° |24.6° |- |Nissan Pathfinder |9.2 |32.6° |24° |22.3° |- |Nissan Frontier |10.1 |32.6° |23.3° |22.3° |- |Lada Niva |8.8 |40° |35° |40° |- |Toyota FJ Cruiser |9.6 |34° |30° |27.4° |- |Toyota HiLux Surf or 4Runner |9.1 |30° |26° |?? |- |Toyota Tacoma (TRD4x4) |9.4 |35° |26° |21° |- |Range Rover |11.3 |35° |29° |150° |- |Land Rover Discover series3 |9.5 |37° |29° |?° |- |VW Touareg |9.3 to 11.8 |33° |33° |27° |- |Mercedes GL class |7.9 to 10.9 |33° |27° |° |- |Ford Expedition EL |8.7 |24.1° |20.9° |18.7° |- |Subaru Outback 2.5xt |8.7 |19° |23° |21° |- |Mercedes [[Unimog]] 132in |17 |27° (bumper dependent) |47° |38° |} (Table information was derived from the maximum values as reported by manufacturer. Trim options and age may change actual values per vehicle) ==See also== * [[:Category:All wheel drive vehicles]] * [[Limited slip differential]] * [[Off-road vehicle]] * [[Sport utility vehicle]] * [[Dune bashing]] * [[Rock crawling]] * Audi [[quattro (four wheel drive system)]] * [[Jeep four wheel drive systems]] * [[SH-AWD]] * [[BMW xDrive]] ==References== {{reflist}} ==External links== {{commonscat|4WD Vehicles}} {{Automobile layouts}} [[Category:Off-road vehicles]] [[Category:Automobile layouts]] [[Category:Automotive technologies]] [[de:Allradantrieb]] [[es:Tracción a las cuatro ruedas]] [[fr:Transmission intégrale]] [[ko:4륜구동]] [[id:Penggerak 4 roda]] [[it:Trazione integrale]] [[ja:四輪駆動]] [[nl:Vierwielaandrijving]] [[nn:Firehjulsdrift]] [[no:Firehjulstrekk]] [[pl:AWD]] [[ru:Полный привод]] [[simple:Four-wheel drive]] [[sk:4x4]] [[fi:Neliveto]] [[sv:Allhjulsdrift]] [[zh:四轮驱动]]