Transmission Comparison - FWD, RWD, AWD

The transmission of a car consists mainly of an engine and a transmission. The rest, the parts that take power from the transmission and send it to the wheels, are the parts that really determine how the car behaves on the road. Different mechanisms work for different environments, and they all provide a different experience for the driver. Manufacturers and brand-loyal enthusiasts love to rant about numbers and performance, but what do the different powertrain options actually offer?

Front-wheel drive

It is known that front-wheel drive cars are on average lighter than their counterparts. The transmission layout also leaves plenty of room under the car, where the driveshaft, center differential, etc. would normally be placed. This means manufacturers can fit the transmission in a neat little package at one end of the car, giving passengers more legroom and trunk space.

How does it work?

Without going into too much detail, all the usual transmission components are present in a front-wheel drive vehicle, the only difference being their orientation and location. You will find the engine, transmission and differential connected to a transversely mounted engine.

Longitudinally mounted engines that send power to the front wheels do exist, but they are very rare and in any case have a layout similar to XNUMXWD cars, meaning that the power is usually returned to the transmission under the car between the driver and passenger before moving. to the differential in the same housing, directing it to the front wheels. It's like Subaru's symmetrical all-wheel drive without power transfer from the driveshaft to the rear axle.

In a transverse engine, the cylinders are arranged from left to right instead of front to back.

While this arrangement may seem counter-intuitive, it actually allows many important components to take up a small footprint, while still operating like a much more complex transmission most of the time. With a transversely mounted engine, the transmission can be located mostly next to it (still between the front wheels), transferring power to the front differential and then to the axles. The assembly of a gearbox, differential and axles in one housing is called a gearbox.

This type of installation can be found on rear or mid engine vehicles, the only difference being the location (on the rear axle).

This lightweight and simple device allows manufacturers to fit smaller, more fuel-efficient engines under the hood.

Front wheel drive benefits

• Front wheel drive vehicles tend to be lighter and carry more weight than front wheel drive vehicles. This provides a good balance for reliable traction. It also helps with braking.

• Fuel efficiency is an important argument in favor of vehicles with this type of transmission. While superior traction allows them to use fuel more efficiently regardless of engine size, smaller engines use less gasoline, and lighter weight means the engine has to haul less.

• Rear wheel traction is significantly better when they are not transferring power to the ground. When cornering, the car is subjected to a large side load, which is why the rear wheels struggle to maintain traction. When the rear wheels fail to maintain traction, oversteer occurs.

  • Oversteer is when the rear of the car wobbles due to the rear wheels losing traction, and this can cause the car to lose control.

• Drivetrain components that take up a lot of space are not under the car, allowing the body to sit lower and giving passengers more room.

• Handling characteristics are predictable and less aggressive than other transmission layouts. New drivers or cautious drivers benefit from this.

Disadvantages of front-wheel drive

• With front-wheel drive, the front wheels take on a lot of the work. They are responsible for steering, most of the braking and all the power that goes to the ground. This can cause traction problems and understeer.

  • Understeer is when the front wheels lose traction when cornering, causing the car to go out of bounds.

• The front wheels can only handle a certain amount of horsepower before they are no longer useful for fast cornering. While everyone loves cars with a little bump, too much power causes the front wheels to abruptly lose traction. This can make a dry paved road look like ice.

Is front wheel drive right for your needs?

• Cities and urban environments are ideal for front-wheel drive. Roads are generally well maintained and there are not many open areas for high speed driving and cornering.

• Commuters and other long-haul drivers will appreciate the ease of maintenance and economy of front-wheel drive vehicles.

• Novice drivers should start with a front-wheel drive car. This can allow them to learn how to drive an easy-to-handle car and keep them from doing too many dangerous stupid things like donuts and power slides.

• Front-wheel drive vehicles have better traction on slippery roads compared to rear-wheel drive vehicles. Anyone who lives in an area with little snow or a lot of rain will benefit from a front wheel drive car.

Rear drive

A favorite of automotive purists, rear-wheel drive still has a lot to offer the modern driver. Currently, this arrangement is mainly used in sports and luxury cars, it was used in almost every car produced in the first half of the twentieth century. The main draw is the intuitive layout and precise handling characteristics that rear-wheel drive offers. The rear wheel drive layout is often seen as the standard vehicle layout.

How does it work?

The simplest transmission layout, rear wheel drive puts the engine at the front of the car and sends it back through the transmission to the rear differential. The differential then sends power to the rear wheels. Simple models and books aimed at young people and children almost always portray it as "how a machine works", and for good reason. On top of the fact that front-to-back power flow is visually easy to understand, having one axle control power while the other steers makes a lot of sense.

In the standard layout, the engine is located longitudinally in front, and the transmission is located under the car between the driver and passenger. The cardan shaft passes through a tunnel built into the housing. A few sports cars, such as the Mercedes SLS AMG, have a transmission at the rear in the form of a rear gearbox, but this arrangement is technically complex and only found on high-end sports car racing cars. Rear-engined, rear-wheel drive vehicles also use a rear gearbox that puts all of the weight on the drive wheels for superior traction.

Handling is the most important factor for those who love rear-wheel drive. Handling characteristics are predictable but very much alive. Rear wheel drive vehicles can usually be made to turn into corners relatively easily. Some see it as a problem, others like it so much that the whole motorsport is based on this principle. Drifting is the only motorsport where drivers are judged on style rather than speed. Specifically, they are judged on how well they can control their car's oversteer in corners and how close they can get to walls and other obstacles without completely hitting them.

Oversteer is like espresso. Some people cannot live without it, while others feel completely out of control. Plus, too much will give you a stomach ache, and the crash that follows when you overdo it can really make you rethink your priorities.

Large luxury sports cars like the BMW M5 or Cadillac CTS-V use rear wheel drive to make the big cars more agile. While all-wheel drive also works to improve performance, it also contributes to understeer more than rear-wheel drive. This is a big problem for heavier vehicles that need extremely sharp handling in order to quickly turn corners without difficult maneuvering.

Rear wheel drive benefits

• Precise handling as the front wheels don't transfer power to the ground and lose traction.

• The lighter weight at the front, combined with the lack of power at the front wheels, means there is very little chance of understeer.

• Intuitive layout makes troubleshooting easy. The location of noise or vibration is easy to determine when the entire transmission is moving back and forth along the line.

Disadvantages of rear wheel drive

• Poor traction on slippery roads due to very low weight on the drive wheels. Some drivers put sandbags on their rear wheels in winter to reduce gas mileage and provide better traction.

• Some people argue that rear-wheel drive is obsolete, citing advances in all-wheel drive and front-wheel drive that make them perform the same way. In some cases, rear wheel drive cars are made to capture nostalgia. Such is the case with the Ford Mustang and Dodge Challenger.

• If a rear-wheel drive car has a live axle at the rear, that is, an axle without independent suspension, then steering can be clumsy and uncomfortable.

Is rear wheel drive right for your needs?

• Drivers who live in a warm area that doesn't get particularly heavy rainfall won't experience most of the disadvantages of rear-wheel drive.

• Those who want a sporty feel can achieve this even in a rear wheel drive non-sport car.

• Powering only the rear wheels, rather than all wheels, provides better fuel economy than four-wheel drive and provides better acceleration at speed.

Four-wheel drive

Four-wheel drive has been gaining popularity over the past two decades. Initially, manufacturers thought that all-wheel drive would mainly appeal to those who wanted to travel off-road. Instead, they found that many people like the way 200xXNUMXs perform on pavement and dirt roads at higher speeds. Rallies, which take place most of the time off-road, have adopted four-wheel drive very quickly. Because rally racing was created to race cars that normal people could buy from the lot, manufacturers had to make sporty XNUMXWD cars available from the factory to meet homologation requirements. This means that in order for a car to compete in rally racing, the manufacturer would have to produce a certain number of cars per year for consumers. Sedans such as the Mitsubishi Lancer and Subaru Impreza were produced in large numbers, while faster Group B cars such as the Ford RSXNUMX were produced in fairly small numbers.

This has really pushed automakers to implement all-wheel drive in their sports cars. It also meant that better, lighter all-wheel drive systems were developed to stay competitive. These days, all-wheel drive is a standard feature on everything from station wagons to supercars. Even Ferrari has used four-wheel drive in the last two cars.

How does it work?

Four-wheel drive is commonly used in front-engined vehicles. While Audi and Porsche are producing all-wheel-drive models that don't have a front-mounted engine, the number of cars that this description applies to is still small. In front-engined vehicles, there are two common ways four-wheel drive works:

The system that distributes power most evenly involves transferring power through the transmission to the center differential. This is similar to a rear wheel drive layout, only with a driveshaft running from the center differential to the differential at the front axle. In the case of the Nissan Skyline GT-R, a rare car in the US, the base model was actually a rear wheel drive car. The Audi Quattro system also uses this layout. The power distribution between the two axles is usually 50/50 or in favor of the rear wheels up to 30/70.

The second type of all-wheel drive layout is more like a front-wheel drive car. The engine is connected to the transmission, which is in the same housing as the front differential and axles. From this assembly comes another driveshaft going to the rear diff. Honda, MINI, Volkswagen and many others use similar systems with excellent results. This type of system generally favors the front wheels, with a 60/40 ratio being the average for higher performance vehicles. Some systems send as little as 10% of the power to the rear wheels when the front wheels are not spinning. Fuel economy is improved with this system and it weighs less than the alternative.

All-wheel drive benefits

• Traction is greatly improved by sending power to all wheels. This greatly improves performance off-road and on rough roads. It also improves acceleration in high performance applications.

• Perhaps the most versatile transmission layout. The main reason why XNUMXxXNUMXs are popular with tuners and weekend enthusiasts is that they can perform a variety of functions both on- and off-road.

• The weather is less of a concern when your car can send power to the wheels that have the most traction. Snow and rain are easier to ride.

Disadvantages of all-wheel drive

• Better traction on slippery roads can make the driver overconfident in their ability to stop or turn, often resulting in an accident.

• Fuel economy is worse than alternatives.

• Heavy. More detail means more weight no matter how you cut it.

• More details means more things that can go wrong. To make matters worse, there is no true standard all-wheel drive system, so parts are not as replaceable as they are in rear-wheel drive cars.

• Unusual handling characteristics; each manufacturer has its own quirks in this department. However, some XNUMXWD systems are ridiculously easy to handle, while others are terribly unpredictable (especially after modification).

Is all-wheel drive suitable for your needs?

• Anyone who lives in a very snowy area should seriously consider getting a four wheel drive vehicle. Getting stuck in the snow can be especially dangerous in rural areas.

• Those who live in warm, dry places don't need all-wheel drive for extra traction, but I still like the performance aspect. Although fuel economy is worse.

• Usually four-wheel drive in the city is redundant. However, smaller XNUMXxXNUMXs can be great in snowy cities like Montreal or Boston.