The drive system is one of the most important features of a car and it is designed to prompt its dynamic movement. There are three main drive systems that are utilized in modern cars: All-Wheel Drive, Front-Wheel Drive, and Four-Wheel Drive.
All-Wheel Drive (AWD)
The All-Wheel Drive system functions by distributing torque between the front and rear axles, which helps avoid slip and loss of traction. AWD is a recent technological innovation. Most modern cars that employ this system use sensors to monitor traction and wheel speed.
There are two different types of AWDs, full-time AWD, and part-time AWD. AWD is always engaged and provides varying amounts of power to the axles depending on traction conditions. All-wheel drive systems primarily power one set of axles, either front or rear. When the car feels traction loss in one axle, it will automatically divert more power to the other axle to compensate.
However, not all AWD systems utilize the same power ratio. Some systems exclusively power the front axle and only rebalance engine output to the rear when the front tires are losing traction.
Front-Wheel Drive (FWD)
The Front-wheel drive system, or FWD, is arguably the most common drivetrain and can be found in vehicles of different makes. FWD cars are designed to send maximum power to the front wheel.
Front-wheel drive vehicles are known for their simplicity, and the system is designed to help save cabin space. FWD vehicles typically get better fuel efficiency and also produce fewer emissions. Most of the cars on the road today are front-wheel drive vehicles, including almost all models of SUVs.
Front-wheel drive SUVs come equipped with additional parts that automatically route some of the engine's power to the rear axle when necessary. Since the drivetrain is positioned in the front and pulls the weight of the vehicle, the effect of oversteer (rear end of the vehicle sliding out and causing a tighter turn than intended) is limited. FWD cars are good at climbing hills and perform well in slippery conditions.
From a manufacturer's standpoint, FWD vehicles are beneficial because they are cheaper to manufacture and use space more efficiently.
Four-Wheel Drive (4WD/4X4)
The Four-wheel drive system, or 4WD, or 4X4 is designed to transfer power to the transmission and then to the transfer case, which is divided between the front and rear axles. 4WD cars equally distribute power to all four wheels. 4X4 is usually offered on vehicles with truck-type platforms. Drivers who want to save fuel can turn off their 4X4 system and operate the vehicle in RWD. Furthermore, 4WD vehicles can be driven on almost any terrain.
Some people mistake all-wheel drive with four-wheel drive. Both systems are designed to engage all four wheels of a vehicle, but there are some notable differences between them. All-wheel drive is designed to help maintain traction when driving on wet roads and it is typically used in vehicles with car-type platforms.
Four-wheel drive cars are mostly intended for all terrain and off-road use. This system is useful for climbing steep inclines which requires more traction, driving across deeper water and other non-typical surface requirements. Enabling 4WD systems sends power to all four wheels using front and rear differentials, plus a transfer case that provides equal distribution of power, regardless of traction. Certain 4WD vehicles have two gear ranges, high and low.
The low gear range is quite handy when low-speed climbing power is required. There are three different mode toggle options in modern four-wheel drive vehicles. Full time, automatic and part-time.
- Full-time systems - are always engaged
- Automatic systems - switch between 2WD and 4WD automatically, and
- Part-time systems - require the driver to switch between two-wheel drive and four-wheel drive modes manually. It is important to note that driving a part-time 4WD vehicle on the pavement with 4WD enabled can damage the vehicle's drivetrain.
Do you need All-Wheel Drive or Four-Wheel Drive?
This depends on what your particular set of driving circumstances is. If you use your vehicle in moderate weather and surface conditions, like regular intensity rain and light snow, a Front-Wheel Drive system will suffice. All-wheel drive vehicles are useful if you need it for light off-road driving and moderate winter conditions. But if extra power is required to, for example, conquer harsh winter conditions and heavy snow, or you need a vehicle that can handle off-road terrain driving, a four-wheel-drive vehicle with high ground clearance and a low gear range is what will get the job done, with no major issues.
Keep in mind that AWD and 4WD systems add extra weight to the vehicle so your fuel consumption is bound to go up. These systems may also cause an increase in drag and thereby reduce the performance efficiency of your vehicle.