Rear-wheel drive

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Rear-wheel drive (RWD) is a form of engine and transmission layout used in motor vehicles, in which the engine drives the rear wheels only. Until the late 20th century, rear-wheel drive was the most common configuration for cars. Most rear-wheel drive vehicles feature a longitudinally-mounted engine at the front of the car.

Layout

The most common layout for a rear-wheel drive car is with the engine and transmission at the front of the car, mounted longitudinally.

Other layouts of rear-wheel drive cars include front-mid engine, rear-mid engine, and rear-engine.

Some manufacturers, such as Alfa Romeo, Lancia, Porsche (944, 924, 928) and Chevrolet (C5, C6, and C7 Corvettes), place the engine at the front of the car and the transmission at the rear of the car, in order to provide a more balanced weight distribution. This configuration is often referred to as a transaxle since the transmission and axle are one unit.

History

1890s to 1960s

Many of the cars built in the 19th century were rear-wheel drive, often with the engine mounted at the rear of the car. The first rear-wheel drive car with the engine mounted at the front was an 1895

to be placed in-line with the engine output shaft, spreading weight under the vehicle. In comparison, a vehicle with the engine over the driven wheels eliminates the need for the drive shaft (replacing this with the transaxle of lighter combined weight), but has the disadvantage of concentrating all the weight in one location.

In order to reduce the relative weight of the drive shaft, the transmission was normally split into two parts: the gearbox and the final drive. The gearbox was normally produced with its highest gear being 1:1, which offers some mechanical advantages. The final drive, in the rear axle, would then reduce this to the most appropriate speed for the wheels. As power is the product of torque and angular velocity, spinning the shaft faster for any given power reduces the torque and allows a lighter shaft construction.

In an era when petrol was cheap and cars were heavy, the mechanical advantages of the front-engine, rear-wheel-drive (FR) drivetrain layout made up for any disadvantage in weight terms. It remained almost universal among car designs until the 1970s.

1970s to present

After the

In Australia, FR cars remained popular throughout this period, with the

forgo a centre rear seat and divide both seats by a centre tunnel.

In the 21st century, most cars are FF, including all front-engined economy cars, though FR cars are making a return as an alternative to large sport-utility vehicles. In North America, GM returned to the production of FR-based luxury vehicles with the 2003

in 2011 and the Australasia-only Falcon in 2016. Excluding trucks, vans, and SUVs, the Mustang is the only FR vehicle remaining in their lineup.

See also

• All-wheel drive
• Individual wheel drive
• Four-wheel drive
• Front-wheel drive
• Drive wheel
• Rear mid-engine, rear-wheel drive layout
• Rear-engine, rear-wheel drive layout

References