[ 13 min read ]
There are 4 types of vehicle drivetrain
If you’re searching for a new vehicle, chances are the terms front-wheel drive (FWD), rear-wheel drive (RWD), all-wheel drive (AWD) or four-wheel drive (4WD) will be somewhere on the listing. These are 4 types of the drivetrain of the vehicle. The drivetrain is the system that connects the transmission to the drive axle. It transfers the power generated by the engine to the wheels.
What exactly do they mean and are there any major differences between them?
There are significant differences that exist beyond which wheels receive power. All four drivetrains have their advantages and disadvantages that affect the way the vehicle behaves and defines its handling, especially in inclement weather. We’re covering the basics before we dive into which layout is best suited to a given situation and different types of driving. Let’s take a closer look at what they are and help answer any questions you may have.
Front-Wheel Drive (FWD)
In a front-wheel-drive vehicle, the transmission channels the engine’s power to the front wheels only. This means that the engine, at the front, is connected to the front wheels, which negates the use of mechanical components to send power to the rear.
FWD is nowadays common in daily driven vehicles because of its stability and efficiency. It has less weight which means better fuel economy. The engine is mounted either sideways or longitudinally which puts weight on the front wheels and because of this there is better traction while driving. The transmission and differential are connected with one unit called a transaxle. Complex universal joints connect the wheels to the axle, allowing a smooth transmission of power while the wheels turn. This does cause increased wear on tires and suspension, as the front wheels are responsible for steering.
There is no driveshaft going from the front of the vehicle to back cause all the powertrain is a single unit in the engine compartment, this increases interior space as there is no space occupied by the rear differential.
Advantages:
- more room in the rear seats for occupants
- cheaper to make, as there are fewer components involved
- in slippery conditions, like in snow, the weight of the engine over the front wheels means that there is more grip
- low weight, because all the components are in front and one additional differential and driveshaft which transfers the power to the rear axle is removed
- better fuel economy
Disadvantages:
- generally less fun to drive - essentially 'pull' rather than push
- usually less-well made
- inherently nose heavy, as the engine and all the mechanical parts relaying the power are kept in the same location
- chances of oversteer at a high-speed cornering
- in low traction conditions, the front wheel will lose traction making steering ineffective
Rear-Wheel Drive (RWD)
Rear-wheel-drive vehicles rely, as the term implies, on their rear wheels for motion. It is the oldest drivetrain used in vehicles, today most vehicles have RWD cause it provides better handling on dry surfaces. RWD systems use a long driveshaft that transmits power from the engine in the front of the vehicle to the differential at the rear axle. The driveshaft is connected to transmission and differential via universal joints which helps the driveshaft rotate easily. The rotation motion of driveshaft rotates the differential and the differential rotates the wheels RWD allows you to “steer with the throttle” and control how much the vehicle rotates with the gas pedal. This also lets you power out of corners better than FWD and carry more speed through longer turns. Get it wrong, though, and you’ll spin out. Especially for novices not used to RWD, slides can be difficult to recover from.
RWD vehicles are most suited to those looking for the most sporty driving experience both on the street and the track. Looking for a little extra fun that If these characteristics don’t seem particularly appealing to you, it may be best to stick to front or all-wheel drive vehicles.
Advantages:
- better handling in dry conditions, because the rear wheels will have more grip on a dry surface
- better weight distribution - more balanced
- can handle more power
- usually better-made vehicles
- better driving experience
Disadvantages:
- more expensive
- less compact
- easy to oversteer
- the overall weight of the is increased because the components are increased
- handling can be tricky if the driver is new
- traction on slippery condition is not good
All-Wheel Drive (AWD)
All-wheel drive it's a drivetrain that employs a front, rear and center differential to provide power to all four wheels of a vehicle. Due to less torque steer, it provides better traction and can feel more stable which is important if you live in snowy climates or regularly drive on wet roads or sand. This makes driving in the snow or rain a less stressful experience, however, in case of a slide happening - all four tires lose traction in this scenario.
AWD system helps the vehicle to have a good launch, power out of corners quicker than the other two drivetrains, has better handling, and also utilizes complete power from the engine.
Advantages:
- better acceleration
- increased grip and control under all road conditions
- sportier handling and traction to a broader range of vehicles
- works all the time (mostly the computer decides according to the condition)
- higher re-sale value
Disadvantages:
- higher price
- complexity - more parts to potentially service
- reduced fuel economy
- increased weight and complexity of vehicles
- not as good in extreme off-road conditions
4-Wheel Drive (4WD)
In a nutshell, it’s a system that sends power to all four wheels equally and without vectoring (controlling the division of power delivery between the wheels or axles), meaning each wheel will spin at the same constant rate as all the others. Power flows from the engine, through the transmission, and normally into a device known as a transfer case that divides it between the front and rear axles.
The equal split of power is great for maneuvering through tough and low-traction situations, but it isn’t very friendly on the pavement. Driving a four-wheel-drive vehicle on solid ground can make simple actions like turning around in a tight street very difficult because the wheels are no longer in sync. Imagine yourself doing a u-turn. In a 4WD vehicle, the inside wheel has to turn more slowly than the outside wheel, which is covering more ground. You might hear a rubbing noise or feel the vehicle hopping when you approach full lock. This is why most 4WD systems are part-time systems that can be disabled by the driver allowing the vehicle to operate in two-wheel drive in normal conditions to improve on-road drivability, but still offers four-wheel traction when you need it.
Advantages:
- best traction in off-road conditions
- more power
- it can be switched to two-wheel drive to improve fuel economy
- proven, rugged technology
- additional weight contributes to better grip on the road
Disadvantages:
- complexity
- it can’t be used in all conditions
- more expensive to purchase
- higher maintenance cost
- added weight increases the braking distance
The difference between AWD and 4WD
Both drive all four wheels so in one sense there is no difference except that AWD has become an accepted description for a vehicle that drives all of the wheels, all of the time. 4WD is generally accepted as a vehicle that uses a driver-selectable system that mechanically engages the drive to all four wheels.
All-wheel drive is a much more recent innovation, and it’s a little bit more complicated, but also considerably more user-friendly. While a four-wheel-drive system tries to send as much power to the four wheels as equally as possible for maximum traction, all-wheel drive is all about varying the amount of power sent to each wheel, either mechanically or electronically.
At this point, you might be wondering why there's a need for both of these types of systems, since the aim of both is to distribute power to all four wheels. The difference between the two layouts is relatively minor, but it has a big effect on what you can tow, and how far off the beaten path you can go.
All-wheel drive is often associated with road-going vehicles while four-wheel drive is more for regular off-road use.
AWD isn’t quite as robust as 4WD, and it can’t match the acute power delivery necessary for low-speed off-roading like rock crawling. AWD does have some clear advantages over 4WD, though. These days, computers are involved in most AWD systems. Sensors on each wheel monitor traction, wheel speed, and several other data points hundreds of times per second. An engine control unit (ECU) analyzes traction conditions and decides which wheel receives power. This type of system, usually called torque vectoring, has allowed massive improvements in handling and all-weather capability.
Ultimately, the system you choose largely depends on your driving needs and where you live. Four-wheel drive is your best bet if you plan on using your vehicle off-road and in difficult terrain on a regular basis. It’s normally found on SUVs and pickup trucks that boast the durability to match the ruggedness of a four-wheel-drive system. All-wheel drive is often associated with road-going vehicles - and for most people, AWD makes more sense.
Summary
If you are rookie driver FWD is probably the best choice for you considering ease of driving, reliability and fuel efficiency. RWD is a good choice if you need more powerful vehicle and you're an experienced driver as it tends to sideway if you accelerate harder. If you looking for regular road and occasional off-road driving, AWD is best as it has the most grip. 4WD is strictly for offloading only can not be used in day-to-day road driving.