Four-wheel drive

Four-wheel drive (4WD) /for-wheel dryve/ noun (uncountable)

Four-wheel drive is a vehicle drivetrain system that powers all four wheels, typically featuring a manually selectable transfer case with high and low gear ranges for optimised off-road capability. This is the original, uncompromising method for conquering the planet's least hospitable terrain. It is a system of rugged, mechanical honesty, involving chunky levers, whining gears, and a complete disregard for on-road refinement. Unlike its more sophisticated cousin, all-wheel drive, four-wheel drive is not a subtle safety aid for a wet roundabout; it is a blunt instrument for dragging a vehicle out of a bog or up the side of a mountain. For Britain, it is the technology that gave the world the Land Rover.

The Full Story of Four-Wheel Drive

While the concept of powering all four wheels is as old as the car itself, its legend was forged in the mud and chaos of the Second World War. The American Willys Jeep was a masterpiece of military utility, a tough, simple, go-anywhere vehicle that became an icon of Allied victory. It was this humble Jeep that would directly inspire Britain's greatest contribution to the world of off-roading.

The story goes that Maurice Wilks, the chief designer at Rover, was using a surplus Jeep on his farm in Anglesey and wondered if Rover could build a British equivalent. In 1948, the Land Rover was born. It was an exercise in pure, unadorned function. Due to a post-war steel shortage, its simple, slab-sided body panels were made from an aluminium alloy called Birmabright, which had been used for aircraft. It was built on a sturdy box-section chassis and equipped with a simple, robust, selectable four-wheel-drive system. It was designed as a "go-anywhere, do-anything" tool for farmers, and it was a runaway success.

Thanks to the remnants of the British Empire, the Land Rover spread across the globe, becoming the default vehicle for explorers, aid agencies, and armies. For many people in the developing world, a battered, endlessly repairable Land Rover was the first car they ever saw.

For decades, four-wheel drive remained the preserve of such utilitarian workhorses. The moment it became civilised was in 1970, with the launch of the Range Rover. This was another stroke of Land Rover genius: a car that combined the unstoppable off-road capability of its sibling with the comfort and performance of a luxury saloon. With its powerful V8 engine, long-travel coil spring suspension, and a permanent four-wheel-drive system, it created the luxury SUV market out of thin air.

Today, traditional, selectable four-wheel drive is a rarity, found mostly on serious off-road vehicles and pickup trucks. Its principles, however, live on in the sophisticated, computer-controlled systems that give modern SUVs their impressive, if rarely used, all-terrain ability.

For The Record

What is a transfer case?

It is a secondary gearbox that takes the drive from the main gearbox and splits it between the front and rear axles. It is the heart of a traditional 4WD system and typically contains a set of low-range gears for multiplying the engine's torque at very low speeds, essential for climbing steep hills or crawling over rocks.

What is the real difference between 4WD and AWD?

Traditionally, 4WD is a part-time, selectable system with a low-range gear option, intended for serious off-road use and not for continuous driving on dry tarmac. All-wheel drive (AWD) is typically a full-time system designed for on-road use to improve traction in all conditions, and it usually lacks a low-range option. Marketing departments have now blurred these lines almost completely.

Why can't you use traditional part-time 4WD on a dry road?

Because it lacks a centre differential, the front and rear axles are locked together and forced to rotate at the same speed. When a car turns a corner on a high-grip surface, its wheels need to rotate at different speeds. A locked system fights this, creating immense strain in the drivetrain, a phenomenon known as "wind-up" or "binding," which can cause serious damage.

Was the Land Rover really made from aircraft material?

Yes. In the post-war steel shortage, Rover had access to a large supply of Birmabright, an aluminium alloy used for aircraft skin. This was perfect for body panels as it was lightweight and corrosion-resistant. The original light green paint was also said to be surplus aircraft cockpit paint.

Is a modern Land Rover Defender a "proper" 4x4?

Yes, but in a very different way. While the original was a purely mechanical affair of levers and gears, the new Defender uses a highly sophisticated, computer-controlled permanent four-wheel-drive system with a selectable low range and electronically locking differentials. It is vastly more capable and comfortable than its ancestor, but it achieves this with silicon chips rather than brute mechanical simplicity.