by Mario

Created on: February 21, 2007   Last Updated: January 29, 2012

The main difference between 4WD (Four Wheel Drive) and AWD (All Wheel Drive) is AWD has a center differential, and is designed to be used all the time.

Every car has, at least, one differential. This is to allow a "differential" of speed between two wheels. This is very important because, when a car is turning, the inside wheel turns slower than the outside wheel. This is because the inside wheel has a shorter distance to travel. Because of this, there has to be a mechanism that will allow the wheels to spin at different speeds, i.e. a differential. (The car would "hop" if it didn't have this).

4WD cars do not have a center differential. That means, there is nothing to let the front wheels spin faster or slower than the rear wheels. They turn the same speed, no matter what. Not a good thing when you're turning. This is why 4WD cars must only be used when it's slippery, because it will put too much stress on the transfer case (the part of the transmission that transfers power to the front or rear wheels, depending on whether you have rear wheel drive or front wheel drive normally). So, 4WD is good for off road and when it's slippery (ice, snow). Also, because you usually use only 2WD, you don't waste as much petrol (gas) as you would if an AWD car.

AWD cars have a center differential. This is why they are AWD all the time. All four wheels can spin at different speeds when they need to, and you have power to all four wheels, which helps keep the car very stable. However, AWD is not good for off-road driving.

So, to summarize, 4WD is good for off-road and saves on petrol, AWD is good for all weather but not for off-road.

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