All wheel drive and four-wheel drive: Explained

The demand for four-wheel drive and all-wheel drive cars in India is not as much when compared to other countries as they cost a lot in our market because they have more mechanical parts than the conventional SUVs and have less fuel efficiency. These drive trains help in acceleration, provides more traction and can get you out of sticky situations but they have their downside too. These systems decrease the fuel economy, add to the cost of the vehicle and increase the maintenance cost.

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Many people think that all-wheel drive and four-wheel drive is the same thing. However, that is not the case both the systems are different and work differently. Today we explain what is all-wheel drive and four-wheel drive.

Four-wheel drive

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A four-wheel-drive mechanism is usually used in pick-up trucks and proper off-roading SUVs. It can be divided into two types: full-time four-wheel drive and part-time four-wheel drive. The power from the engine goes from the engine to the clutch/torque converter then to the transmission and finally to a transfer case. The transfer case is that equipment that divides the power between the axles. Four-wheel drive cars come with a front differential, a rear differential and a transfer case which sits between both differentials.

The full-time 4×4 transfer case has a limited-slip differential that splits the torque between the front and rear wheels whereas the part-time 4×4 transfer case can send all the power to either all the wheels or just the rear wheels. The driver has to manually choose that he wants to send the power to all the four wheels or just rear wheels from the transfer case. Also, the power is divided equally between all the four wheels which helps in tackling surfaces with less traction. However, the four-wheel-drive system is not so great on the road as it is off the road. Driving all the four wheels at the same time and making tight turns at the same time causes the mechanical parts to suffer from a strain.

You may hear a rubbing noise or your car may hop when you reach steering’s full lock. This is known as binding or wind-up. To avoid this strain on the mechanical parts, most of the four-wheel-drive cars come with a part-time switch that allows you to shift the car to the rear-wheel-drive configuration at a flick of a switch. When the drive flicks the switch the front wheels are disconnected from the power train which means they are not getting any power from the engine. This saves a little bit of fuel and wear and tear of the mechanical parts of the four-wheel-drive system.

All-wheel drive

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The all-wheel-drive system is a more recent invention and more complicated when compared to four-wheel-drive systems. But it does come with its advantages as the driver does not have to worry about the complexity of the system as it is fully controlled by a computer. The power from the engine travels to the clutch/torque converter then to the transmission and then to the central differential. Then, that central differential sends the power to one of the axles all the time.

The biggest advantage of all-wheel drive is that a computer decides that the power should be sent to which of the axles so the driver does not have to do any thinking. One other advantage is that the all-wheel-drive system does not suffer from binding or wind-up. The power is usually sent either to the front axle or the rear one and if the system detects a slip then only it sends the power to the other axle to gain traction back. This also helps in fuel efficiency because it is not necessary that all the four wheels are being powered all the time.

So, this is how a four-wheel drive and an all-wheel-drive system works. For most people all-wheel drive makes more sense as it is cheaper to maintain and the driver does not have to worry about anything. Four-wheel drive is made for the people who go for proper off-roading in woods.