What Every Student in Automotive Mechanic Training Should Know About Four-Wheel Drive

become an auto mechanic

For most vehicles, and under most driving conditions, standard two-wheel drive is more than sufficient. In some cases, though, having only two wheels powered by the engine might not be enough: if you spend a lot of time driving on unpaved dirt roads, for example, or through heavy snow. In these situations, having four-wheel drive or not might be the difference between getting home and staying stuck in a snowbank on the side of the road.

This is why graduates of automotive mechanic training know a thing or two about four-wheel drive. Read on to learn the differences between four-wheel drive and all-wheel drive, how they work, and what the advantages and disadvantages are.

The Difference Between Four-Wheel Drive and All-Wheel Drive

The terms four-wheel drive and all-wheel drive are often used interchangeably, but students in automotive training should understand the difference between the two.

Four-wheel drive (4WD) generally refers to a part-time system. In part-time 4WD systems, the vehicle runs like a standard two-wheel drive whenever the 4WD is not engaged. When there is a lot of snow or ice on the road, or when a driver is going off-road, they can engage the 4WD. Gears inside of the transfer case split the torque being produced by the engine between the front and rear differentials, sending power to all four wheels.

In an all-wheel drive (AWD) vehicle, power from the engine is similarly split between the front and rear differentials, but in this case, it can’t be turned off. This is also the case in what’s known as fulltime four-wheel drive vehicles, though fulltime 4WD generally features a locking centre differential, while AWD does not.

Most Jeep Hummers are 4WD, though AWD is also available in some models
Most Jeep Hummers are 4WD, though AWD is also available in some models

If You Want to Become an Auto Mechanic, Here’s how 4WD Works!

As students in automotive mechanic training will know, the rotational power produced by an engine is called torque. The drivetrain in your car transfers that torque to the wheels, but in order for the torque to move your car, the wheels need to have traction on the road, otherwise the wheels will simply spin in place.

With two-wheel drive, it’s the two wheels that are receiving power from the engine that need to have sufficient traction. If they’re stuck in snow or sand, for example, and can’t gain traction, then you won’t be able to move. With four-wheel drive, each wheel is receiving power from the engine, so as long as one or more of those four wheels can gain traction, you can keep moving.

The benefits should be obvious to anyone who’s ever gotten just two of their wheels stuck in mud or snow and been unable to drive, despite the other wheels being planted firmly on dry ground. With four-wheel drive, this doesn’t happen.

With two-wheel drive, having just some of your tires stuck in mud or snow can be a serious problem
With two-wheel drive, having just some of your tires stuck in mud or snow can be a serious problem

There Are Some Disadvantages to Four-Wheel Drive As Well

For those pursuing auto careers, it’s important to note that four-wheel drive comes with some disadvantages as well. The main disadvantages are cost and fuel consumption. Four-wheel drive will add costs to the purchase price of a vehicle, and unsurprisingly, an engine requires more fuel to power four wheels than two. It can also add weight to a vehicle, which can increase its stopping distance.
Nonetheless, for anyone regularly driving in low-traction conditions, four-wheel drive can be a tremendous benefit.

Are you interested in training for a career in the auto industry?

Contact Automotive Training Centres for more information about how to become an auto mechanic.

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