Tap to Read ➤

Types of All Wheel Drive Vehicles

Stephen Rampur
The types of all wheel drive (AWD) vehicles are generally classified as per the technology that drives all wheels on a part-time or full-time basis. In this story, you will find some basic information about the types of AWD vehicles.
A very useful and most prominent technology used in automobiles is All Wheel Drive, sometimes also known as Four Wheel Drive (4WD), if the technical working is not considered. The primary use of this system is to provide power and traction to all wheels when the need arises. The fundamental differences between 4WD and AWD is that the former one offers a facility to be activated from a two wheel control mode.
On the other hand, AWD runs on a full-time basis and can't be engaged or disengaged manually. By ruling out the technicalities of these systems, car brands may use AWD and 4WD interchangeably for marketing vehicles. The main difference found in the types of all wheel drive vehicles is the manner in which the drive setup functions.
Though the technical functioning of 4WD and AWD is different, the basic concept to run all axles and wheels remains the same. In order to understand the types of AWD vehicles, let us assume AWD and 4WD to be the same.

All Wheel Drive Vehicles

The AWD or 4WD technology can be incorporated in any kind of vehicles such as hatchbacks, sedans, coupes, SUVs and crossovers, pickup trucks, minivans, military trucks, and so on. As cars like sedans and coupes are mostly to be driven on standard roads, they are fitted with a simple four wheel control technology.
But when it comes to SUVs or pickups, complex systems are considered, owing to off-road potential of the vehicle. Car brands normally have a trademarked name for their 4WD and AWD systems that come in different setups which are discussed in the following paragraphs.

All Wheel Control Patterns

Part-time All Wheel Control

As the name suggests, a part-time 4WD system is one in which the all-axle control can be activated when required. The driver starts with two wheel control at first, but when there is a slippery or snowy road ahead, he can manually shift to all wheel control.
This shift is generally done using a lever or a switch in modern vehicles. The wheel control change can simply be done while driving. In a part-time 4WD, both front and rear driveshafts are connected, which is why all the wheels spin at a constant speed.
The Command-Trac I is a similar kind of system on the Jeep Wrangler. It allows the driver to drive in two wheel drive mode, and shift to a four wheel traction manually when needed.

Full-time All Wheel Control

Next comes the full-time 4WD system, which is a permanent all wheel and axle control, unlike in part-time system. In vehicles fitted with this type of setup, the driver cannot manually control the engine powering the axles and wheels. So, no matter which surface you are driving on, the system will always be active.
Automobiles with full-time 4WD system necessarily have a center differential, which does the job of enabling all wheels to spin at variable speeds. This is actually how AWD works. A suitable example would be the Symmetrical All Wheel Drive system set up in Subaru vehicles, wherein the all wheel control cannot be activated or deactivated manually.

Automatic All Wheel Control

Automatic 4WD is associated with a computerized system that activates all wheel control when required, much in the case of a wheel slip.
When the driver drives on a smooth surface, the vehicle runs on two wheel mode; but when the car gets on a slippery surface and a wheel slip occurs, the electronic system automatically detects loss of traction and activates AWD control. Some advanced systems even get activated before there is a wheel slip.
Once the car is in traction, the system is deactivated and gets back to two wheel drive. Automatic 4WD functions much in synchronization with the Electronic Stability Control system. The automatic activation of the system is beneficial for the driver to concentrate more on road and his driving, instead of worrying about manually switching drive controls.
A similar technology can be found in the Honda CR-V, named as 'Real Time Four Wheel Drive System'. Power to all wheels is supplied by the car's computer system only on the occasion of a wheel slip.

Selectable All Wheel Control

A selectable all wheel drive system is not so popular, but is considered useful and convenient for drivers. This system incorporates more than standard technology for rendering and distributing power to all wheels. In this system, the driver has to manually select if he wants a two wheel drive or a four wheel drive.
One major aspect is that it also enables to select between two types of all wheel control. The driver can select between all wheels being powered with the same amount of torque or the power being automatically distributed to all wheels individually when required.
Technically put, you can select between a part-time four-wheel drive or a full-time AWD. This working pattern can be found in the Suzuki SX4 Crossover. It is termed as the intelligent All-Wheel-Drive (i-AWD).
In this system, the driver can choose three drive modes; viz., standard, i-AWD Auto, and i-AWD Lock. The first mode is for two wheel drive, the second is for all wheel control with each wheel getting different levels of torque, and the third being the front and rear wheel axles getting equal power.
This is some brief information of types of all wheel control working patterns. Car companies might use any of the formats mentioned above for AWD systems in their vehicle offerings.
A notable technical difference between 4WD and AWD is that the former system is a part-time, four-wheel control, whereas the latter is a permanent powering of all wheels. Be it any kind of all wheel control, these systems truly help the driver to safely control the car on challenging surfaces.