Difference Between All Wheel Drive and 4WD

When looking to buy a car, you normally come across the phrases “all wheel drive” and “ four wheel drive (4wd)” thrown around and frequently interchangeably. If you are not a boorish car nerd, then kudos to you if you are not, you may actually not know that these two phrases are not interchangeable. The phrases actually refer to different systems, which provide drastically different results.

So you will wonder, what the heck are these differences and why at all should they matter to you? In this article we’ll briefly give an overview of both these automobile systems and how the function.

Four-Wheel Drive

Let’s begin with the old school version. Four wheel drive also referred to as 4WD, 4×4 or Four by Four, is normally used to describe off road vehicles.

Power is transferred from the transmission to a transfer case. This gear system splits power between the rear and front axles to make maximum torque reach every wheel. This piece of engineering was good enough to beat the German Nazis, and it still remains good enough to take your Jeep over a pile of rocks and rough terrain. Despite having a heroic heritage, it does come with its fair share of drawbacks.

When power is evenly split by the transfer case, it makes sure that each wheel rotates at the same velocity. This can be very problematic when you are doing turns. For instance. For a car t turn, the inner wheel has to rotate slower than the other wheel, which covers more ground. If the vehicle fails to do this, the inner wheel will lose traction and spin freely. This, as you may guess is not a great feature for moving the vehicle forward efficiently.

All-Wheel Drive

An All-Wheel Drive is a recent innovation, and as you may guess, more complex. This feature appears in just about everything like supercars with super performance such as the Audi R8, SUVs and crossovers like the Volvo XC90.

One major difference between four wheel drive and all-wheel drive is the all-wheel drive system is always on every time you drive. Well, mostly. And there are two types of AWDs: electronic and mechanical.

An ideal of achieving a competent mechanical all-wheel drive system is by making use of three differentials. A differential is box that contains gears as well as other engineering magic that allow power to be drawn from transmission and split at different levels between the rear and front axles. In an all-wheel drive, the systems works to distribute power to wheels that have the most traction by evenly splitting power between the rear and front axles on the middle differential as well as the separate wheels by rear and front differential.

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