The basics guide to drivetrain layouts
Your car’s engine produces a lot of power, but without a system to send that power to the wheels, you wouldn’t really get anywhere. A drivetrain, quite simply, works to send power from the engine to the wheels. It includes parts like the transmission, driveshaft, axles and wheels. As you’ll see, they come in many configurations, each of which affects your driving experience in a different way.
What are the four types of drivetrain layouts?
Since an engine would never be able to move the wheels without them, drivetrains have been around as long as cars have. Naturally, they’ve evolved quite a bit over time. Today, there are four main types, each with their own unique characteristics:
Rear-wheel drive (RWD) was the first drivetrain system used in an automobile. As the name suggests, it transfers the engine’s power to the rear wheels. A vehicle’s weight naturally shifts to the rear as it accelerates. By transferring engine power to the rear wheels, the weight on the rear is increased even further, resulting in better traction during acceleration.
Front-wheel drive (FWD) cars are the opposite of rear-wheel drive — they transfer power to the two front wheels instead. Since many vehicles have engines up front, running a drivetrain to the front wheels typically requires a much more compact setup. A smaller drivetrain weighs less, which improves fuel economy. This has helped popularize it in modern cars.
A four-wheel drive (4WD) powers all four wheels simultaneously. Four-wheel drive automobiles have better handling and traction, so they're well-suited for rough terrain and off-roading. Four-wheel drive often needs to be engaged manually.
An all-wheel drive (AWD) is very similar to a four-wheel drive in that power is applied to all four wheels. Traditionally, these were designed for increased traction on pavement as opposed to outright off-roading, though newer models have more rugged capabilities. Usually, all-wheel drive is engaged automatically.
Is all-wheel drive the same as four-wheel drive?
Not quite, though the terms are increasingly becoming interchangeable. As technology advances, the lines between them get blurry. Traditionally, an all-wheel drive was always on automatically while four-wheel drive required manual activation. These days, both types might offer different modes of activation and levels of traction control. Generally, four-wheel drive cars are better for intense off-roading while all-wheel drive vehicles were designed more with pavement or gravel in mind.
Pros and cons of different drivetrains
Each type of drivetrain has advantages and disadvantages. Knowing the differences can help you make an informed decision.
Rear-wheel drive pros
When you punch the gas, a rear-wheel drive transfers power and weight to the back of the car. This allows for maximum acceleration on a dry surface. Additionally, this frees the front wheels to be used purely for steering. Skilled racetrack drivers can even use this to slide their way through tight corners, but this is a risky maneuver even for pros.
Rear-wheel drive cons
On the other hand, cars with rear-wheel drive tend to be at a disadvantage in harsher weather. Modern innovations like traction control have helped improve performance, but rear-wheel drive cars don’t usually perform as well as other drivetrains in inclement weather. You may also lose out on interior cabin space — if the car’s engine is up front, a large driveshaft will be needed to connect the engine to the back wheels.
Front-wheel drive pros
Front-wheel drive has become increasingly popular over time. Since most cars keep the engine up front, powering the front wheels (located directly underneath) requires a much shorter drivetrain. This reduces weight, as well as the energy loss inherent to transferring power further away from the engine. Both of those advantages further serve to increase fuel economy — a growing concern for buyers and manufacturers. Finally, front-wheel drive cars often boast better traction while driving since the weight of the engine bears directly down onto the driven wheels.
Front-wheel drive cons
A frequent performance disadvantage that front-wheel drive suffers from is a phenomenon called “torque steering.” This occurs when unequal power gets applied to one wheel over another, causing the car to veer to one side when accelerating. Additionally, the weight of the engine bearing directly down on the driven wheels increases wear and tear on them.
Four-wheel and all-wheel drive pros
Transferring power to all four wheels results in improved handling, especially in slippery conditions. This advantage makes four-wheel drive and all-wheel drive cars ideally suited for rough terrain, and popular choices in places where inclement weather regularly makes driving difficult. Some cars may even have different modes or levels of torque to offer even more control.
Four-wheel and all-wheel drive cons
The flipside? The added complexity and weight make these drivetrain systems less fuel-efficient and add significantly to the cost, both up-front and over time.
What is the best drivetrain?
Given all your options, it makes sense to wonder which is best. When it comes to drivetrains, however, it’s like asking which car is the best. Everyone will have a different answer. As you’ve seen, each one has a distinct offering. A helpful way to find your answer is what you’re doing now — learning about the options.
A note on tires
Most experts agree that your tires will have a greater impact on your car’s handling than its drivetrain. You may not always be able to choose your car’s drivetrain, but you can make the choice to drive on the most appropriate tires.
Rear-wheel drive and front-wheel drive cars have been popular for a long time, but other drivetrain types are catching up. What you decide to go with is up to you. Combining your newfound knowledge with the help of a trusted dealer can help determine what drivetrain best meets your needs.