Front Wheel Drive, Rear Wheel Drive, All Wheel Drive and 4x4

Whether or not you drive something right-off-the-lot brand new, something preowned, or your driving your friend’s Jeep and don’t know anything about it – its always a good idea to have a basic idea of the assortment of drivetrains that are out there for most automobile situations. We’re going to talk about the four main drivetrains you might see throughout your car, truck, SUV, sports car or convertible driving life.

Front Wheel Drive (FWD or 2WD)
Some examples of vehicles with 2WD; Grand Caravan, Chrysler Pacifica, 2WD Jeep Compass,  FWD Jeep Cherokee, Fiat 500.

This is what you’ll most likely encounter in small cars, some smaller SUVs and minivans. A front wheel drive powertrain system routes the power from the engine and is amplified in the transmission then supplies it to the front wheels of the vehicles – usually called an axle or a differential. Forward motion is generated from the FRONT wheels.  Front wheel drive systems are typically the most common as they are economical to build into a vehicle. It also requires less physical space on the vehicle and weighs less than a 4x4 or AWD system – simply because you have fewer components involved. They also use the weight of the engine pressing down the front of your car to create the best traction possible when the wheels are spinning.

 

Rear Wheel Drive (RWD)
Some examples of vehicles with RWD; Dodge Viper, 2WD RAM trucks, Fiat Spider 124 Convertible, Dodge Challenger, Dodge Charger.

Like the front wheel drive system; A rear wheel drive powertrain system routes the power from engine and is amplified in the transmission then supplies it to the rear wheels of the vehicles. Forward motion is generated from the REAR wheels. This may not provide the best traction but does enhance certain things like steering and handling. You will almost only ever see this on performance vehicles, sports cars and trucks. Therefore, you usually see some vehicle manufacturers build their convertibles/sports cars with the engine in the rear. The weight presses down on the rear of the vehicles, causing the spinning tires to better grip the road.

 

All Wheel Drive (AWD)
Some examples of vehicles that can have AWD; Dodge Charger, Dodge Durango, Fiat 500X.

You’ll usually see AWD systems in SUV’s, crossovers and some cars. AWD is handy, because it really is a decision-less system. It provides maximum traction during acceleration and handles well on sloppy road conditions and moderate off-road terrain. Majority of AWD systems provides power to one set of wheels on a full-time basis. When the vehicle detects slippage or resistance, it will automatically transfer power to the other set of wheels as well. Essentially, transferring a FWD to a 4x4 when needed. Not all systems are the same – some vehicles always have percentage of power transferred to the secondary set of wheels, like Subaru for instance. Then adjusts power output as needed, to compensate for slippage, traction etc.

 

Four Wheel Drive (4x4 or 4WD)
Some examples of vehicles that can have 4x4; 4WD RAM trucks, Jeep Grand Cherokee, Jeep Renegade, Jeep Wrangler, Jeep Compass, Jeep Gladiator.

The biggest reason 4x4 differs from all wheel drive is that the driver has complete control over when the 4x4 system is engaged and disengaged. When you’re in a situation that may require extra traction and you don’t want the computer to decide when or how long you need if for, this is the advantage to a complete 4x4 system. Some vehicles do come with an auto mode, which automatically engages the 4x4 system when the vehicle detects traction or slippage issues.

 

Let’s talk about some other options that may be a selection on your 4WD dial or lever.
4x4 High – A general rule of thumb, 4x4 high is used for a vehicle that’s moving faster than a steady parking lot speed. Usually used when driving through snow, ice, muddy conditions or other slippery situations you might anticipate. Please keep in mind, you usually don’t want to drive much fast than 80km/hr – even in 4-high as it can cause damage to your transfer case.
4x4 Low - 4-Low generates a greater amount of torque than the aforementioned 4-High. You’d typically use this setting in more dire situations. To avoid damage - you don’t want to drive faster than 20-30km/hr on this setting.

 

A little about the Mechanics

There is something called a transfer case which is the main power distributor to most 4x4 and AWD systems. After the transfer case (t-case) receives power from the transmission, it sends it to the axles and the wheels are turned, causing movement. It also synchronizes the difference between the rotation of the front and rear wheels.

 

 

 

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Here’s a generalized image of a transfer case. Without going into a tonne of detail, here’s the basics.

 

You’re cruising along with power being supplied from your car’s transmission via the input shaft. Energy is transferred to one end of your vehicle, causing either the front or rear output shaft to spin – providing power to the single axle being used to propel your vehicle.

 

Either you or your vehicle decides it/you need some extra traction. The clutch level is disengaged when the 4x4 system is activated causing power to also transfer to the second output shaft. Causing it to spin, and in turn, causing the other set of wheels to propel.

 

 

There’s a variety of sensors and other pieces of mechanics and technology in order for the vehicle to properly and safely run a 4x4, AWD, FWD or RWD system.

Some Maintenance tips;

Transfer cases have fluid in them. It’s VERY important to make sure you service them at their regular service intervals as set out by your product’s maintenance guide. If you are 4x4, towing or use your 4x4 system regularly – it is a good idea to do them a little more often. A transfer case can be very expensive to repair or replace and it’s a shame to have to perform a major repair when it could have been prevented by some relatively simple maintenance. Most people couple their transfer case service around the same time their transmission and/or their differentials/axles may need servicing. Also, just to clarify, your axles are probably due for servicing more often than your transfer case.

Most FCA vehicles; such as RAM 1500, RAM 2500, RAM 3500, Jeep Compass, Jeep Renegade, Jeep Grand Cherokee, Jeep Cherokee and others that require such maintenance are generally due around 96,000KMs – but this varies on the type of vehicle. That’s why it is imperative you check your vehicle’s maintenance guide.