The terms 4WD (four-wheel-drive) and AWD
(all-wheel-drive) are similar technologies- which involve the transmission of power to all four wheels,unlike that of normal vehicles in which either the front or rear wheels are driven. Most SUVs and Pick-up trucks offer 4WD or AWD systems, some compact cars like the Audi A4, Mercedes C-class,Toyota matrix and Mitsubishi Lancer have AWD variants as well.
Many manufacturers have ended up confusing consumers with obscure names like 'Active 4WD’, ‘Real-Time 4WD’, ‘Quattro’,‘4matic’,‘Xdrive’ ‘Quadra-drive’ etc.
It is important to know the optimal type required prior to the purchase of a vehicle.
There are different types of 4WD and AWD systems,which are optimized for different terrains – hence,it is important to know which
one best suits ur need(s).
4WD types
1. PART-TIME 4WD:This is a system that can only be used part of the time in four-wheel
drive mode. It is designed
to be used in adverse terrain conditions and can not be used on a dry pavement (Doing so will wear out the transfer case and
result in serious mechanical
damage). The settings range from 2WD,4WD High and
4WD Low. Vehicles with this type of
4WD transfer about 25% of the torque to the driven wheels
when in 4WD High or 4WD Low setting. In some older systems, the vehicle must come to a
complete stop before the 4WD
mode is engaged, but in newer variants ,it could be done while the vehicle is in motion (this is called ‘Shifting-on-the-fly’) as
long as the speed of the vehicle does not exceed 50km per
hour. The 4WD ‘Low’ setting should only be engaged in extreme terrain conditions.
This type of 4WD system is best for people who don’t need 4WD, but occasionally encounter terrains that need the extra grip. Examples of
vehicles with such systems
are the Toyota Hilux,Mitsubishi Montero Sport,Nissan Xterra, Jeep Wrangler, Pre-1999 Toyota 4Runner and Mitsubishi
L200 Pick-Up,
2. FULL-TIME 4WD: This is also called permanent 4WD. The additional feature of a
differential incorporated into the transfer case makes it possible to use 4WD at all times. This more advanced form of 4WD allows you choose between 4WD ‘High’ or 4WD ‘Low’ setting, but can remain engaged while on dry pavement. Some Full time 4WD systems like that of the Range Rover don’t have the traditional 4WD High or 4WD Low settings; instead a rotary knob is used to pre-select a setting. Vehicles with this type of 4WD system
are very good off-roaders. Examples are the Toyota Land cruiser, first generation Mercedes ML, Mercedes G-class,Lexus GX470 and Land Rover Defender,Range Rover/Range Rover Sport.

AWD Types.
1. FULL-TIME AWD: The main difference between full-time AWD and Full-time 4WD is that full-time AWD lacks the ‘Low Range’ gearing
feature. Vehicles with these feature can be used on all surfaces (including dry pavement). AWD was designed to improve traction on all road surfaces and as a result, has an added safety advantage because of the extra grip. Certain performance cars like
the Bugatti Veyron, Audi
R8, Nissan Skyline GTR,Lamborghini Murcielago, Aventador and Gallardo possess permanent AWD to improve traction and overall handling.
It should be noted that these systems often have varying torque-distribution ratios – some use a 45-55 ratio
(45% to the front, 55% to the rear),which could be described as a rear-biased permanent AWD setup, some have a 50:50 ratio while some others have a 60:40 distribution ratio.
Some variants have ‘smart’
systems which vary torque
distribution depending on the road conditions being encountered.
While most vehicles with permanent AWD lack serious off-roading ability, some Vehicles possess AWD systems that perform well off-road
despite the absence of a
‘low-range’ e.g 2006-2011
Mercedes ML,1st generation VW Touareg and Porsche Cayenne. Some AWD Dodge Durangos and Toyota 4runners have ‘low-range’ settings – and are also good off-road.
2. AUTOMATIC AWD:
This AWD systems are
passive in nature, vehicles
with these form of AWD
run in 2WD (either front-
wheel-drive or rear-wheel-drive) most of the time. When the onboard electronics detect
any loss of traction or slippage at the primary driven wheel, the AWD system locks and
automatically distributes
power to all four of the wheels until normal traction is restored, after which it reverts to the default 2WD mode. These activities are often imperceptible to the driver and take milliseconds to engage. Vehicles with this form of AWD have absolutely no adverse terrain capabilities and are meant for on-road driving. Examples are the Toyota RAV4, Honda CRV, Nissan X-Trail, Nissan
Murano, Lexus RX and the
Infiniti EX, FX and JX cross-overs.

Summary: The main difference between the two drive systems is the 'low range' gear in the 4WDs. The Low range gear slows down the vehicle and increases the torque available at the
axles. Low-range gears
are used mainly during extreme off road maneuvers, such as
rockcrawling, or when
pulling a heavy load. This
particular feature is often absent on vehicles equipped with AWD.

*BMW SUVs equipped with the 'xdrive' AWD system are terrible offroaders (X3,X5 and X6). They were designed for onroad driving and were never intended for challenging trail conditions.

Very educative.
In addition, 4wd almost always have a switch or flip that the driver must manually engage.
AWDs don't have such. They transmit power to each individual tyre based on feel and road conditions.
Well done

zyl_kenny: Very educative.
In addition, 4wd almost always have a switch or flip that the driver must manually engage.
AWDs don't have such. They transmit power to each individual tyre based on feel and road conditions.
Well done

In most systems, yes...

platinumricky haz said it all. depends on wat u using it for though in a place like naija u need 4wheel drive. in advanced countriez u need awd.

Very gud we have that AWD system in Hyundai ix35

What about Mercedes-Benz 4matic system? How cool is it?