4WD and AWD EXPLAINEDPosted On: July 15, 2014 By : AutoLife Team
Whether you drive a hatchback or an SUV, all that power under your vehicle’s hood is useless if the engine’s torque doesn’t get to the drive-wheels. Many drivers have common misconceptions about 4WD and AWD systems. New innovations in four-wheel and all-wheel drive have only made that confusion worse for new drivers. So, we’ve decided to help explain the hype surrounding the 4WD and AWD systems.
What is 4WD?
Most cars on the road today move by using two wheels, either through the rear (RWD) or the front (FWD). 4WD, on the other hand, uses all four wheels to move the car forward. By mobilizing all four wheels, it can move the vehicle even if one of the wheels doesn’t have traction. This system powers all four wheels at all times and aids in stable driving off-road – on sandy, muddy or slippery surfaces. The 4WD system is normally used on large SUV Four-Wheel Drive (4×4) vehicles.
In this system, power goes from the transmission to a transfer case where it is divided between front and rear axles. There are two types of 4WD systems:
Part-Time 4WD – It refers to a system that can only be used part of the time in four wheel drive. The part-time 4WD was created to provide a vehicle with more traction to either carry maximum loads or to travel in rough terrains. Part-time 4WD systems have to be used in 2WD mode on pavement, cement or other hard, sticky surfaces. They are designed to be engaged only in specific situations when you need extra traction and damage can occur if driven on hard surfaces. Part-Time 4WD usually includes 2WD and two speeds range Hi and Lo. Some vehicles with part-time 4WD are Jeep Wrangler and Toyota Tundra etc.
Full-Time 4WD – It refers to a 4-wheel-drive system that can be operated at all times on all surfaces. In full time 4WD, the torque is supplied to all four wheels at all the time. It can be used on all surfaces including the pavement. Typical lever or switch settings available on full-time 4WD are 4WD Hi and 4WD Lo. The additional feature of a differential incorporated into the transfer case makes it possible to use 4WD all the time. Some vehicles with full time 4WD are Land Rover, Range Rover, Toyota Prado etc.
What is AWD?
All-Wheel Drive (AWD) is similar to full time 4WD because it also powers the all four wheels of a vehicle at all times. They work on all surfaces but due to the lack of “low range”, AWD vehicles are much less robust as compared with 4WD. They are less effective in off-road settings. In an AWD system, each system has a different front-to-rear power delivery ratio.
In this system, sensors monitor traction, speed and other data. Computers determine power to be generated on each wheel. There are two types of AWD systems:
Full time AWD – It is similar to the full time 4WD but it lacks the slow speed torque enhancing low range feature. It is not intended for off-road conditions. The focus of full-time AWD is to impose on-road stability and performance. Some examples of full time AWD vehicles are recent Mercedes M-Class, Subaru Forester etc.
Automatic AWD – It was created mainly as a stability enhancing system. Automatic AWD can be used full time on all surfaces. However, they lack off-roading capabilities. Some examples include the new-generation Toyota RAV4, Honda CRV, etc.
Some 4WD Facts
- The first 4WD vehicle was designed by Ferdinand Porsche (founder of Porsche cars). He designed the vehicle when he was 25 years old.
- First mechanical 4WD was built by the Dutch company Jacobus Spyker in 1902.
- Four Wheel drive auto company (FWD) built the first US vehicle in 1911. FWD supplied 4WD trucks to both British and US Marines during WW1.
- The first 4WD Formula 1 racing car was the Ferguson P99 Climax. It was the first 4WD car and the last front-engine car to ever bag a spot in a F1 event.
- The most radical 4WD vehicle is one made by a Russian armour-car builder Russo Baltique called Dartz Prombron Monacco Red Diamond Edition which was claimed to be the world’s most expensive vehicle at a time.
- World’s first pedal powered 4WD vehicle was created by a German fellow, Frank Fraune and called it the Trailcart. The Trailcart is a metamorphosis of a mountain bike and 4WD with 290 Nm of torque.
- Australians are the world’s biggest buyers of 4WD vehicles.
Different Drive-Line Setups
4×4 (four by four)
It refers to vehicles with 4 wheels powered by 4 wheels. It can either by 4WD or AWD. “4×4” in a 4WD vehicle means there are 4 wheels total and 4 wheels that are driven. Some examples include Honda CR-V, Range Rover, Kia Sportage, Tata Safari Storme, etc.
6×6 (six by six)
It refers to vehicles with 6 wheels powered by 6 wheels. Mercedes-Benz G63 AMG 6X6 is a 6WD vehicle.
4×2 (four by two)
It refers to vehicles that have two-wheel drive with four wheels. It’s basically a 2WD (two wheel drive) system. “4×2” in a 2WD vehicle means there are 4 wheels total and 2 wheels that are driven. Some examples include the Dacia Duster, Toyota Hilux, Nissan Navarra, etc
8×8 (eight by eight)
It refers to vehicles with 8 wheels powered by 8 wheels. Usually military vehicles are 8WD drive.
Basics of Off-road Driving
2WD H2: Lever at “H2”
Use this for normal driving on dry, hard-surfaced roads. This position provides better economy and a smooth ride
4WD H4: Lever at “H4”
Use this for normal driving on wet, icy or snow-covered roads. This position provides greater traction than two-wheel drive.
Use this for maximum power and traction. Use “L4” for climbing or descending steep hills, off-road driving, and hard-pulling in sand, mud or deep-snow