Rear-wheel-drive layout with engine positioned longitudinally under the hood.

The Engine's Mandate Driving the Rear Wheels Let us speak plainly about the arrangement of machinery. An engine produces force. That force must reach the wheels to move the vehicle. In a rear-wheel-drive configuration, the engine's directive is clear: transmit power to the wheels situated at the back.
Typically, this involves an engine positioned longitudinally – crankshaft pointing front-to-back – often located under the hood at the front of the chassis. This orientation facilitates a direct path for power, channeled through a transmission, down a spinning driveshaft, into a differential nestled between the rear wheels, and finally out through the axles to turn those wheels.
The front wheels, in this fundamental layout, are left solely with the task of steering. It is a separation of duties, engineered. This mechanical layout is not arbitrary; it brings inherent physical characteristics. Placing the engine at the front and driving the rear wheels allows for a *potential* distribution of weight that can approach equilibrium, particularly when accelerating, as load transfers rearward onto the driven wheels.
This can enhance traction during launch. Furthermore, divorcing the steering function from the propulsion function at the front wheels eliminates the phenomenon known as torque steer – that tugging sensation felt through the steering wheel under hard acceleration in some front-wheel-drive cars. The demands on the front tires are purely directional control and braking.
The architecture, however, dictates certain spatial realities. The driveshaft requires a tunnel, often intruding into the passenger compartment, reducing footwell or central console space. Compared to a compact front-wheel-drive transaxle unit, the separate transmission, driveshaft, and rear differential add component count, complexity, and mass.
In conditions of low traction, such as snow or ice, an unladen rear-wheel-drive vehicle can struggle for grip compared to a front-wheel-drive counterpart where the engine's weight sits directly over the driven wheels, unless aided by modern traction control systems, appropriate tires, or skillful driver input. The engine itself, while the source of power, is intrinsically linked to the drivetrain choice by its placement and orientation.
A longitudinal mounting, common in front-engine, rear-wheel-drive vehicles, simplifies the routing of exhaust systems and provides space alongside the engine block for steering mechanisms and suspension components. While mid-engine and rear-engine layouts driving the rear wheels also exist, altering the vehicle's weight balance and handling dynamics significantly, the fundamental principle remains: the engine's rotational energy is conveyed specifically to the rear axle.
* System Specifications & Characteristics:

Power Delivery** Engine output directed exclusively to the rear axle via transmission, driveshaft, and differential.

Engine Orientation Typically longitudinal (front-to-back crankshaft) in front-engine configurations.

Component Layout Separate transmission, driveshaft, rear differential, and rear drive axles.

Weight Distribution Potential for near 50/50 front-rear static balance; dynamic load shifts rearward under acceleration.

Steering/Propulsion Front wheels manage steering; rear wheels manage propulsion.
Eliminates torque steer.

Packaging Requires central tunnel for driveshaft, potentially impacting interior volume.

Traction Dynamics Can exhibit reduced traction on low-friction surfaces compared to FWD unless compensated by weight, tires, or electronic aids.

Load Capacity Often favored for trucks and towing applications due to load transfer characteristics.