The location of the driving axle determines whether the vehicle is classified as
Rear-wheel-drive vehicles can use a conventional layout with the engine at the front of the vehicle. The torque from the engine is transmitted to the rear-mounted driving axle by propeller, or drive shaft. This spreads the weight of components throughout the vehicle.
Some rear-wheel-drive vehicles have the engine at the rear, driving the wheels through a combination transmission and rear axle called a transaxle. The transaxle is lighter than a separate transmission and rear axle.
Moving the engine to the rear allows a lower bonnet line, which improves aerodynamics. The increase in weight over the rear wheels can improve their traction.
A vehicle which has the engine located behind the operator’s cabin, but forward of the rear driving axle is called a mid-engine, rear-wheel-drive vehicle.
A mid-engine design locates the mass of the engine behind the driver but forward of the rear axle. This allows for a low bonnet profile, and good handling.
Most goods-carrying, rigid commercial vehicles locate the engine near the front, and drive the rear axle by a 2-piece propeller shaft. The rear axle supports most of the goods, or payload.
Mini-buses commonly locate the engine at the front of the vehicle, beneath the operator’s cabin, and drive the rear axle by a propeller-shaft.
Larger buses and coaches locate the engine at the rear. This allows the vehicle to have a low floor, and removes much of the noise and vibration from the passenger compartment.
Front-wheel-drive vehicles use the front wheels to pull the vehicle along. In light passenger vehicles it gives lighter body weight, and increased interior room.
The engine and transaxle are at the front, and can be mounted laterally, that is, the engine is parallel to the front axle, or longitudinally where the engine is inline with the centre line of the vehicle.