MOTORING NEWS - Despite the increasing number of online resources and shifting dealer strategies, car shopping is still a headache. 

Add in all the new car segments, vehicle features and technology acronyms and the process becomes daunting.

There's a long list of confusing topics when choosing the right car, but all-wheel drive (AWD) and four-wheel drive (4WD) seem to consistently confound salespeople and car shoppers alike.

Often, these terms are used interchangeably, but are they really the same? In the motoring world, they actually refer to very different systems, which can produce radically different results on and off-road. How does 4WD - or AWD - impact your daily driving life, and which badge belongs on your car?

Four-Wheel Drive (4WD)
Lets start with the old-school version. 4WD, sometimes referred to as Four by Four or 4×4, is typically used on off-road vehicles - or at least vehicles with all-terrain capabilities.

Unfortunately, 4WD doesn't fit neatly in a one-sentence explanation, but we'll stick to the basics.

Power goes from the engine to the transmission, to what is known as a transfer case. 

This system splits power between the front and rear axles so that torque is evenly applied to each wheel. 

This process is nothing new, and is still used in modern Jeeps to tackle just about any off-road obstacle. It isn't perfect, though.

When the transfer case splits power evenly, it ensures that each wheel turns at the same speed. 

This is deeply problematic when doing things like turning. You see, for a car to make a turn, the inside wheel has to turn more slowly than the outside wheel, which is covering more ground. 

If the vehicle can't do this, the inside wheel loses traction and spins freely.

This, as you might be able to guess, isn't great for maintaining momentum.

There are a couple of ways that modern 4WD systems get around this. For starters, most modern 4WD systems are only on when you activate them. 

This can be done electronically or by using that protruding lever that sits somewhere between your radio and the centre console. 

That way, you can use 4WD at low speeds when traction is at a minimum (for example, in snow or mud), but you can enjoy the efficiency of two-wheel drive in normal conditions. 

When left in 2WD, there are fewer moving parts, and therefore fewer restrictions to forward motion. Said differently, you'll save fuel when you don't need to engage 4WD.

More contemporary 4WD systems are activated with buttons or switches rather than a manual lever, and include multiple settings for the 4WD system.

These systems usually have two 4WD gears. "4WD High" splits power less evenly and allows what's called 'limited slip' between the inside and outside wheels. This corrects the problem of a locked, spinning inside wheel by channeling more power to the wheel with traction (in our example, the outside wheel).

4WD High limits available power to the wheels so you can move quickly over slippery surfaces. For the most available power, however, you'll want "4WD Low". The low gear limits wheel speed but is perfect for arduous terrain. A word of advice: you really don't want to go fast in 4WD Low … things start breaking.

All-Wheel Drive (AWD)
All-Wheel Drive is a much more recent innovation and more complicated. It crops up on everything, from supercars like the Audi R8 to sedans like the Subaru. 

In fact, a good rule of thumb might be to think of AWD as the "car" system while 4WD is the "truck" system. 

This isn't always the case, as some vehicle segments overlap with drivetrains. Consider crossovers like the Honda CR-V, Toyota RAV-4, Mazda CX-3 and others to fall under the "car" category, while bigger SUVs from Toyota for example, are in the "truck" or "bakkie" category.

The main difference between 4WD and AWD is that an AWD drive system is on all the time. 

There are two types of all-wheel drive: mechanical and electronic.

The most common way of creating a capable, mechanical AWD system is by using three differentials.

A differential is a box of gears that can take power from the transmission and split it at different levels between two wheels (the front or rear axle) or four wheels (the front and rear axle).

In AWD, this system works to get power to the wheels with the most traction by splitting torque between the front and rear axles on the centre differential, and to the individual wheels by way of the front and rear differentials.

This is useful in slippery conditions when different wheels might be getting different amounts of grip from moment to moment. 

The Mercedes-Benz E63 AMG is a perfect example. It is now sold only in AWD in the United States because its power can overwhelm the traction of the rear wheels alone. 

Even when we aren't talking about 500+ horsepower cars, splitting power evenly means added stability in all types of weather.

AWD isn't quite as robust as 4WD and it can't match the acute power delivery necessary for low-speed off-roading. However, AWD does have some clear advantages. 

The pioneer and industry standard for AWD systems, Audi Quattro, distributes torque mechanically. Quattro allowed Audi to dominate rallying for nearly a decade in the 1980s.

These days, computers are involved in most AWD systems. Sensors on each wheel monitor traction, wheel speed, and several other data points hundreds of times a second. 

An ECU (engine control unit) dictates where power is sent and to which individual wheel, depending on whichever has the most grip.

This type of system, usually called torque vectoring, appears on everything from the Subaru WRX to the Dodge Charger these days. 

Torque vectoring has allowed massive improvements in handling and all-weather capability.

Source: www.digitaltrends.com