question: What are the purpose of 4WD and 2WD in vehicles? As well as each having their own Hi and Low buttons?
comment: 2WD stands for Two-Wheel Drive, either Front or Rear, depending on your car. Most likely, FWD. In Two-Wheel Drive mode, the power of your engine will be sent to a single axle, and split among both wheels on that axle. This is the most common way you'll use your car. The unpowered wheels will roll passively, like the front wheel on a bicycle. In 4WD (Four-Wheel Drive) mode, the engine can deliver power to all four wheels simultaneously, if it detects a loss of traction. Hi and Lo modes refer to the gear ratio being used: Lo provides much more torque at low speeds, which is useful for navigating hazardous situations, such as snow and terrain.
passages: Both "Four High mode" and "Four Low mode" cannot be used on pavement as "driveline binding" and "torque windup" can occur, causing damage to the four-wheel-drive system.
  
  Section::::AdvanceTrac.
   1995 was the first model year to comply with the new US Department of Transportation "high mount brake light" regulation requiring all trucks to have a brake light in the center of the rear at the top of the cab, though a temporary light was added to the 1994 models.
  
  In late 1995, a driver's side airbag was added as well as compliance with the new US safety rules. Rear wheel ABS came with both 2WD and 4WD models beginning in 1990.
   Command-Trac was first introduced using the NP208 transfer case in the full-size Jeeps (SJ series) in 1980. The drive modes are the same as with the Dana 18 and 20 transfer cases: 2Hi, 4HI PT, and 4LO PT. The 4WD modes are not for use on high-traction surfaces such as dry roads. The NP208 was used through at least 1987.
   In 2001, due to the introduction of S.T.E.M., Mini 4WD has been used extensively for educational purposes in schools around the world, for teaching science, technology, engineering and math.
   Predominantly, Explorer was not equipped with "Two High mode" except in the 1995-1996 model years. In model years 1998-up no Two High was available. Only Auto, Four High and Four Low modes were offered. Two High mode was unique to the Expedition, though it was discontinued between the 1999–2002 model years. Two High mode was reintroduced on the redesigned second generation Expedition (U222) for the 2003 model year and featured a new full front axle disconnect system with vacuum operated front locking hubs that would disconnect the front axle, front differential, and front drive shaft when not needed for quieter, more fuel-efficient operation on pavement. Ford claimed that the improved "Two High mode" could help increase fuel economy up to half-a-mile per gallon of gasoline. In Two High mode, torque is routed to the rear drive wheels only, imitating rear-wheel drive.
   Some models fitted with the ATTESA E-TS system (such as the Nissan RS4 Stagea) have a "S" button on the dash. This will bypass the control system of the ATESSA E-TS computer and lock the transfer case into full 4WD. This is to be used at low speeds in snowy/icy conditions only as understeer is greatly increased in this mode.
  
  Section::::Variations.:ATTESA E-TS Pro.
   1984 saw an introduction of 4WD cars that offered better traction thus 2WD car owners found themselves being forced to compete against its all-wheeled counterpart, resulting in the unlimited/modified category being split into its respective drivetrain classes. This division was first adopted by Remotely Operated Auto Racers (ROAR) and Japan Model Racing Car Association (JMRCA) in 1986 to become used in the Worlds in 1987 then became widely used.
   In addition to these basic modes there could be implementations that combine these modes. The system could have a clutch across the center differential, for example, capable of modulating 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
  
  Section::::History.
  
  Section::::History.:Late 1800s.
   The early Marmon-Herringtons proved to be the exception to the rule — 4WD cars and trucks developed in the 1930s were mainly going to be built for governments, with (future) warfare applications in mind.
   Section::::Active Drive.:Active Drive Low.
  
  Active Drive Low includes all of the features of Active Drive I but denotes a greater possible crawl ratio. When in "4-Low" mode the front and rear axles are locked together and power is sent to all four-wheels through the power transfer unit although no low range gear reduction occurs. Active Drive low relies on shorter axle gear ratios while holding first gear in the ZF9HP transmission to achieve a crawl ratio of 20:1; similar in effect to Freedom Drive II.
  
  Applications:
  
  BULLET::::- 2015–present Jeep Renegade (BU)
  
  BULLET::::- 2018-present Jeep Compass (MP)
  
  Section::::Active Drive.:Active Drive Lock.
   Section::::Race Categories, Classes & Types.:Circuit Endurance Racing.
   In 1990, the BBC authorised licencees to manufacture models capable of being bi-wired, but stipulated that the performance in single-wired mode must meet the original specification. KEF started making the bi-wire crossover, designated SP2195, available in 1991.
  
  Section::::Product revisions.:2005 – birth of LS3/5A ""V2"".
   In December 2013, beginning with the model year 2014 D-Max changes in the exterior included daytime running lamps replacing the fog lamps and updates to the rear lamp in L, Z and Z-Prestige model.
  
  Available in 4 models line-up, 3 body type, 3 drivetrains; 2WD, High-ride 2WD (Hi-Lander) or 4WD (V-Cross) in Single cab (Spark), Space Cab and Crew Cab (Cab4) [Spark available only in the 2WD drivetrain. Spark 4WD became available in 2014MY]
   Section::::Types.
  
  Transfer cases used on "part-time" four-wheel-drive off-road vehicles such as trucks, truggies, rock-crawling vehicles, and some military vehicles generally allow the driver to select 2WD or 4WD, as well as high or low gear ranges. Those used in sports cars and performance sedans are usually "transparent" to the driver; there is no shifter or select lever.
  
  Section::::Types.:Drive type.
  
  Section::::Types.:Drive type.:Gear-driven.
   Groups are split according to car specifications, mainly regarding severity of modifications and aerodynamics. With more powerful classes, safety regulations are also tighter. Classes range from "Club"-class, being close-to-production, via the "Pro"-class, with more allowed aerodynamics and allowed engine swaps, to the "Extreme"-class in which everything is allowed, that is not forbidden explicitly. While in lower classes a distinction between 2WD and 4WD is made, this is neglected in the Extreme-class.
  
  The series is independent and not connected to any larger organization like the DMSB. 
  
  Section::::Video games.
   Most series models feature leaf-sprung suspension with selectable two or four-wheel drive (4WD), however series I's produced between 1948 and mid-1951 had constant 4WD via a freewheel mechanism, and the Stage 1 V8 version of the series III featured permanent 4WD. All three models could be started with a front hand crank and had the option of front & rear power takeoffs for accessories.
  
  Section::::Development.
   In the 1960s, as patents on the technology expired, tractor and implement manufacturers agreed on the three-point hitch as the one standard, interchangeable, full-featured system to hitch implements to tractors. With the advent of nonproprietary status, the manufacturers were able to refine the system and create useful modifications. Now, nearly all manufacturers have adopted some standardised form of the modern three-point hitch system; many companies also offer safe adaptation kits for converting the non-standard hitch systems to the three-point hitch system.
  
  Section::::See also.
  
  BULLET::::- Overrunning clutch
  
  BULLET::::- Power take-off
  
  Section::::External links.
  
  BULLET::::- The inventor, Harry Ferguson
  
  BULLET::::- Three-point linkage model
   Quadra-Trac II was introduced in 1999 and it employs a two-speed chain-driven transfer case featuring three modes of operation, "4-All Time", "N" or neutral, and "4-Lo". Two different transfer cases were used, the NV247 in 1999-2004 WJs and the NV245 in 2005-2010 WKs and 2006-2009 XKs.
   BULLET::::- Certain software, anime production companies and some regions in Japan also collaborated with Tamiya to merchandise the main and/or secondary characters of their anime, software mascots or even tourism icons for limited edition Mini 4WD kits through licensing as these companies believed that Mini 4WD is cheaper for them to invest in bulk quantities compared to R/C cars which are four to six times the price per kit in bulk.
  
  Section::::Mini 4WD Design.
   BULLET::::- 2016-present Jeep Compass (MP)
  
  BULLET::::- 2018-present Jeep Grand Commander
  
  Section::::Active Drive.:Active Drive II.
  
  Active Drive II includes all of the features of Active Drive I but adds a low gear range. When in "4-Low" mode the front and rear axles are locked together and power is sent to all four-wheels through a 2.92:1 gear reduction in the power transfer unit; providing a crawl ratio of 56:1 for four cylinder Jeep Cherokees and a 47.8:1 crawl ratio for six-cylinder Cherokees. All Cherokees with this system have a raised ride height of one inch.
  
  Applications:
  
  BULLET::::- 2014–present Jeep Cherokee (KL)
   Section::::Race Categories, Classes & Types.:Street Mini 4WD.
  
  The Street Mini 4WD is an unofficial race category where the mini 4WD cars runs in the open space without circuit with the racer following them and guides the car with the guide stick. One of the basic concepts that the Street Mini 4WD regulation imposes is to be able to develop a mini 4WD car as much as possible similar to a real racing car.
   "Four High" and "Four Low" modes were also featured on both Explorer and Expedition. "Four High mode" tells the intelligent locking multi-disc differential to lock, providing a permanently locked 50:50 torque distribution. The front and rear drive shafts are fully locked, forcing them to rotate at the same speed regardless of tractive conditions. "Four Low mode" also tells the intelligent locking multi-disc differential to lock, however it instructs the BorgWarner transfer case to select low range off road reduction gearing. Reduction gearing is utilized to reduce the vehicle’s speed to a manageable crawl, and to increase (multiply) the supplied torque coming from the engine. Thus the drive wheels have ample torque to move the vehicle at low speeds. It is also used to control downward speeds while descending steep gradients and to improve the vehicle’s off road crawl ratio.
   OKA started in 1986 when a group of Australian mine executives discussed that each of them needed an off-road truck with a three-ton payload and nothing on the market at the time filled those requirements. Those executives formed a consortium and the OKA brand was born.
   During early versions of the game, the 2WD vehicle was not a part of the car roster. In its place was a three-wheeled vehicle called the 3WD, bearing a color scheme very close to the 4WD's blue paint job.
  
  Section::::History.:Marketing.
   The Haldex 4WD system is currently used in the following vehicle models:
  
  BULLET::::- Volkswagen Group (Volkswagen AG)
  
  BULLET::::- Audi A3 quattro
  
  BULLET::::- Audi S3
  
  BULLET::::- Audi RS3
  
  BULLET::::- Audi Q3
  
  BULLET::::- Audi TT quattro
  
  BULLET::::- SEAT León 4
  
  BULLET::::- SEAT Altea Freetrack 4
  
  BULLET::::- SEAT Alhambra 4
  
  BULLET::::- Škoda Octavia 4x4
  
  BULLET::::- Škoda Superb 4x4
  
  BULLET::::- Škoda Yeti 4x4 (Haldex Fourth Gen)
  
  BULLET::::- Škoda Yeti Outdoor 4x4 (Haldex Fifth Gen)
  
  BULLET::::- Škoda Kodiaq 4x4 (Haldex Fifth Gen)
  
  BULLET::::- Škoda Karoq 4x4 (Haldex Fifth Gen)
  
  BULLET::::- VW Golf R
  
  BULLET::::- VW Bora 4motion
  
  BULLET::::- VW New Beetle RSi
  