Types of car drivetrains

When you’re considering a buying new vehicle there are several things to take into consideration, like should I get a small sedan or an SUV? How much technology do I want it to have? What kind of safety features are best? Vehicles come in many different sizes and styles with lots of different features, so there are many things to consider when you’re ready to buy your next ride. One of the most important is to find the right drivetrain for you to find new roads. You most probably have heard the terms drivetrains or powertrains when shopping around for a new car.

What is a drivetrain and powertrain?

Simply put, a drivetrain is the series of parts in your car that work together to make your wheels turn. A powertrain, on the other hand, is basically a drivetrain plus the engine and some other parts.

Types of vehicle drivetrains

When you talk about drivetrain it’s possible that most of us know the types of drivetrains in cars today, but what do they do exactly? What’s the difference? Which one is better out of those? Each has advantages and disadvantages and it’s important to understand each in order to make the right decision in your purchase. The different types of drivetrains are:

1. Front Wheel Drive (FWD)
2. Rear Wheel Drive (RWD)
3. 4 Wheel Drive (4WD)
4. All Wheel Drive (AWD)

For off-roading and getting out of sticky situations 4 Wheel Drive and All Wheel Drive may be your best choice. In nearly all cases, however, Front Wheel Drive and Rear Wheel Drive get the job done, but you’ll want to consider the pros and cons of Front Wheel Drive and Rear Wheel Drive options before making a decision.

1. Front Wheel Drive (FWD)

Front Wheel Drive refers to a car in which the transmission sends the engine’s power to the front wheels. If a vehicle features Front Wheel Drive, the transmission transfers power from the engine to the front wheels. The majority of cars today have a FWD layout. This setup transfers power to the front wheels, giving them the responsibility of moving and steering the vehicle. With Front Wheel Drive, the front wheels are pulling the car and the rear wheels don’t receive any power on their own. A great thing about FWD is that it’s cheaper to design and make than other drives which means the vehicle may be less expensive for consumers.

How does FWD work?

In these vehicles the engine occupies space near the front axle, it later meets to transmission or the transaxle. This is because of the fact that it combines the functions of transmission, driveshaft and differential, thus with the help of a transaxle the engine supplies power only to the front wheels of the vehicle. Starting in 1895, the car manufacturers experimented with front wheel driven vehicles.

Front Wheel Drive surfaced during the 1900s on various prototypes and it emerged into the mainstream during the 1930s when French automaker Citroen released the traction avant which means literally Front Wheel Drive. The most famous and most influential Front Wheel Drive is undoubtedly the original Mini. Small economy cars began shifting to FWD during the 1970s and most new cars sold today use this configuration.

Advantages of FWD

The pros of Front Wheel Drive vehicles are:

• They typically get better fuel economy.
• They emit less carbon dioxide.
• Front Wheel Drive cars are usually more stable. The engine and transmission are located directly above the front wheels which can provide better traction when climbing hills and driving on slippery roads. They can also maintain better traction over small hills or over light snow or ice because the weight of the engine is over the front wheels.
• Front Wheel Drive has fewer components than any other drivetrain setup making the vehicle lighter and improving its gasoline mileage, that’s why most economy type cars are FWD.
• More efficient packaging and usually more passenger space. With Front Wheel Drive all of the mechanics are in the front of the vehicle that means there’s more passenger and cargo space inside the car.
• Front Wheel Drivee is a simpler system so it’s easier and less expensive to maintain.

Disadvantages of FWD

The cons of Front Wheel Drive vehicles are:

• The handling suffers somewhat. Since all the weight is located in the front of the vehicle FWD cars tend to understeer, this means it makes handling more difficult.
• Front Wheel Drive has worse acceleration than Rear Wheel Drive which is why most sporty and race cars use RWD. If you do a lot of driving on winding roads, you’ll likely notice a difference between the two different types.

2. Rear Wheel Drive (RWD)

Rear Wheel Drive is basically the opposite of Front Wheel Drive. RWD is the transmission that sends the engine’s power to the rear wheels. This drive is most commonly found on sports cars and performance sedans. Vehicles that feature Rear Wheel Drive are a bit more complicated. Vehicles handle much better than Front Wheel Drive vehicles and you will notice the difference in curves, turns, and when navigating through traffic situations.

Traction won’t be as good, especially in wet or snowy road conditions. A rear-wheel-drive car of the same weight, power, gearing, and tire size and type will accelerate faster than a Front Wheel Drive car, as the weight of the vehicle is transferred off the front wheels and onto the rear wheels to improve traction. FWD cars typically lose traction in these situations.

How does RWD work?

Rear Wheel Drive means that the power from the engine is delivered to the rear wheels and the rear wheels push the car forward. The front wheels do not receive any power and are free to maneuver the vehicle. The propeller shaft works to transfer the torque from the transmission to the rear wheels through a differential that distributes power between the two wheels. A RWD arrangement needs the engine and the transmission to be mounted longitudinally.

Rear Wheel Drive vehicles are better for towing because the front wheels have better steering without a ton of weight on them, plus with the power transfer and the tongue weight of the trailer the rear of vehicle squats which gives the rear wheels more traction. If you get stuck, adding weight over the rear wheels may help. The Rear Wheel Drive system has been around for many years now with the first example dating back to 1885. Yes, we’re talking of the time when the world’s first car was invented by none other than Karl Benz.

The 1885 Benz Patent Motor Wagon, which is often considered the very first car was Rear Wheel Drive. Rear Wheel Drive cars tend to have a better balance due to a more evenly spread out weight throughout the vehicle. RWD vehicles have more flexible designs as the engine can sit in the front, middle or back of the car, whereas FWD vehicles require the engine to sit at the front.

Rear Wheel Drive can also handle larger engines because the weight and power of that larger powertrain are less likely to burden the front wheels. You’ll find that RWD cars typically feature less interior space than its FWD equivalent, but manufacturers typically install a performance oriented cockpit with seats that offer more support and extra gauges to better monitor the performance of the vehicle.

Advantages of RWD

The pros of Rear Wheel Drive vehicles are:

• Rear Wheel Drive improves handling due to load transfer and acceleration.
• Maintenance cost is less.
• Towing load is easier because the pulling wheels are located closer to the load.

Disadvantages of RWD

The cons of Rear Wheel Drive vehicles are:

• There is less interior space due to more room needed for the transmission and drive shaft.
• It is difficult maneuvering in wet and snowy conditions.

3. 4 Wheel Drive (4WD)

4 Wheel Drive means the power from the engine is delivered to all 4 wheels all of the time when Four-by-Four (4×4) is engaged. The 4WD vehicles are usually equipped with a transfer case which allows the car to change to Rear Wheel Drive transmission in order to save fuel and get back to 4WD mode if and when required. This means you can operate your vehicle in two wheel drive mode in normal driving conditions. 

4WD equipped cars are called Four-by-Fours (4x4s) as the first digit here represents the number of wheels, and the second figure shows the total number of powered wheels. For example, trucks with 6×4 configurations have 6 wheels, out of which only 4 receive power. Most off-road-ready SUVs come with the 4WD system as they offer more traction. It allows you to drive over boulders or steep hills and through deep water.

How does 4WD work?

There is usually a mechanical connection between the front and rear axles. The 4 Wheel Drive system has three main components; the differentials, transfer case and locking hubs.

• Differentials: It is located between the two front wheels and one between the two rear wheels. They send the torque from the drive shaft or transmission to the drive wheels. They also allow the left and right wheels to spin at different speeds when you go around a turn. The differentials enable the speed difference between the inside and outside wheels.
• Transfer case: It is the device that splits the power between the front and rear axles. The transfer case in an All Wheel Drive system contains a device that allows for a speed difference between the front and rear wheels. The transfer case on a part-time 4 Wheel Drive system locks the front axle drive shaft to the rear axle drive shaft so the wheels are forced to spin at the same speed.
• Locking hubs: When 4 Wheel Drive is not engaged the locking hubs are used to disconnect the front wheels from the front differential. Simply from half shaft and dry shaft, the locking hub allows the differential half shafts and drive shaft to stop spinning when the car is in two wheel drive, saving wear and tear on those parts and improving fuel economy. Let’s take the instance of a corner, when you are approaching a corner then in making the turn all four wheels spin at different speeds, but if you were to put the 4WD system on, then the system would try to get all wheels spinning at exactly the same speed, which would basically make on road cornering difficult.

You shouldn’t drive in 4 Wheel Drive mode all the time, only turn it on when it’s needed such as in rain or snow or when you’re off-roading. Specialty of these vehicles is the option to shift to high and low ratios ranges. Low provides maximum traction in an off-road environment and high is for slippery on road conditions like snow ice loose sand or gravel.

Using these, one can have a higher torque output to get out of a sticky situation. The 4 Wheel Drive system was patented back in 1893 by an English engineer Bramah Joseph Diplock. He even made a four wheel drive equipped vehicle to showcase the higher capability in off-road terrain. Of course, there was no looking back ever since and to this day car makers opted for this layout for vehicles meant to go off the road.

Should you buy a 4WD vehicle?

4 Wheel Drive vehicle depends entirely on your driving conditions and how you intend to use the vehicle. Drivers who go off-roading or live in areas with a lot of snow may want to think about the added benefit of 4WD and how comfortable they feel driving in snow without the assistance of 4 Wheel Drive or All Wheel Drive. 4×4 vehicles are known for their ruggedness and versatility. However, due to its Rear Wheel Drive nature a 4WD vehicle might have less traction than its AWD counterparts.

Advantages of 4WD

The pros of 4 Wheel Drive vehicles are:

• Inherent traction advantage in all conditions especially accelerating through turns and as engine power approaches or exceeds a level that can overwhelm two driven tires.

Disadvantages of 4WD

The cons of 4 Wheel Drive vehicles are:

• Added cost weight and friction reduce efficiency in all driving situations.

4. All Wheel Drive (AWD)

An All Wheel Drive arrangement works on pretty much the same principle as 4WD, but in most Front Wheel Drive or Rear Wheel drive as the primary drive mode. The general misconception is that AWD and 4×4 are the same thing. While both of them have all 4 wheels running, and they run on the same principle, there are some key differences that set the two apart. 

While most of the 4×4 send power to the rear wheels if and when required, the AWD cars are mostly FWD or RWD, depending upon the situation. This drive train employs a front, rear, and center differential to provide power to all four wheels of a vehicle. All Wheel Drive is a more expensive option and uses more parts.

How does AWD work?

The big thing that an All Wheel Drive system usually includes is center differential, which is a set of gears that divides the transmission power to the rear and front axles. The engine runs into a transmission and then back to the differential. Usually the engine is longitudinally mounted. Instead of connecting to the rear differential like in Rear Wheel Drive vehicles, the drive shaft connects to the center differential.

All Wheel Drive system will usually have will sensor that can tell if the tires are losing speed or traction, if the sensors detect that a wheel is not performing correctly it will say to the vehicle’s computer to provide extra power as needed. All Wheel Drive cars aren’t as capable off the road as 4 Wheel Drive ones but they do help increase the traction which is something that leads to improved handling capabilities on the tarmac.

Again, AWD isn’t too good off the road but it can definitely help a vehicle get out of a sticky situation. In the best case scenario all-wheel drive suvs can be used for mild off-roading. All Wheel Drive system was invented in 1903, a few years after the 4 Wheel Drive model broke covers. It was the invention of Dutch Brothers Jacobus and Henrik-Jan Spyker and was unveiled through a hill climb racer called Spyker 60 H.P 4WD. While it was promoted as a 4 Wheel Drive it was nothing but an All Wheel Drive layout.

Is AWD the same as 4WD?

While All Wheel Drive system is very similar to 4 Wheel Drive system, they are not exactly the same, but both systems do activate all four wheels simultaneously but differ on how they get to that point. To be classified as AWD cars both axles must be able to rotate simultaneously but at different speeds, while 4WD vehicles have a transfer case AWD vehicles have a center differential that forces both axles to spin at the same speed. The gear and transfer case usually divide the power between the front and rear axles, so both axles deliver the maximum possible amount torque.

Advantages of AWD

The pros of All Wheel Drive vehicles are:

• Better acceleration. With all four wheels putting power usually gaining more speed is easier.
• Better grip in slippery condition. Whether there is snow on the ground or heavy rain coming down, All Wheel Drive will make the wheel grip more when accelerating or maintaining speed.

Disadvantages of AWD

The cons of All Wheel Drive vehicles are:

• Less fuel efficient. Sending power to both axles make the vehicle less fuel efficient.
• More parts mean more weight. Weight makes the vehicle perform worse and use more fuel, more parts mean more things that can break.
• All Wheel Drive vehicles generally cost more to maintain, as services and repairs may cost more down the road.

Which drivetrain is best?

That’s one of the most loaded questions in the automotive world and the answer largely depends on who you ask. The truth is it largely depends on the situation and the application of the system and there is no right or wrong answer. While front wheel driven cars provide better traction due to the weight in the front they also tend to understeer more often.

The RWD vehicles have less costly maintenance than their counterparts but then the additional materials lead to a higher purchase price. Any type of 4WD system is perceived as superior in low traction situations. That makes it most favorable for those who live in regions where it snows quite a bit or where paved roads or a luxury. More recently AWD has become more prominent in performance applications as a way to increase traction.