Majority of the old car models come with part-time 4WD systems, which unfortunately rarely get engaged while on the other hand, the technology for has changed overtime offering a wider variety of systems.
Some of the vehicle manufacturers offer two or even more choices on a single vehicle line with some coming with part-time 4WD or full time 4WD or permanent 4WD or part time AWD or full time AWD or permanent AWD and, therefore, l believe it is important for you the motorist to understand the functionalities of the different systems.
What is the difference between 4WD and AWD?
The difference is 4WD systems have extra low gearing in a separate gearbox for more torque when off-roading while the All Wheel Drive (AWD) do not have this separate low range gearbox.
The benefit of the AWD is that it saves on system complexity and weight with fewer components to wear out and better fuel economy.
So if you don’t plan on doing any serious off-roading or towing, l advice you to stick with a vehicle with all-wheel-drive system because it is idle for the motorist driving around in cities and towns who may require off-roading once in a while.
Let me explain the various terminologies of the various systems for easy of understanding on their functionalities that helps you to pick the vehicle with the systems that favours your driving terrains and the locality whether patents;
Part-time 4WD:
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This is the most basic system out there that gives the driver the choice to engage two wheel or four-wheel drive modes. However, most part-time 4WD systems cannot be engaged unless it is very slippery because the system locks both the front and rear axles together.
Using these systems on dry roads, especially around corners, will cause binding and potential damage to the system.
This is the system that l know many drivers hardly engage as a result of not encountering the need to use it although they bought the car for that purpose.
Full-time 4WD
This system offers the driver selectable two-wheel-drive mode for dry-road or summertime driving, an “auto 4WD” or full-time 4WD mode for unfavorable or constantly changing weather conditions, and a 4WD Low or Lock mode for low range gearing and off-roading.
Permanent 4WD
These permanent systems send power to all wheels at all time, typically with a fixed power split ratio between front and rear wheels.
Many permanent systems can be dynamic in nature, computer controlled with the ability to transfer power back and forth between front and rear axles depending on slippage or upon acceleration and cornering. Being a “4WD” means that there is low range gearing for off-roading or tougher conditions.
Part-time AWD: These systems are typically 100% front-wheel drive based, transferring power to the rear wheels only after slippage to the front wheels occurs.
They require no driver intervention but are less sophisticated than permanent or full-time AWD systems.
Full-time AWD: They can either be a front wheel drive or rear wheel drive biased system until slippage occurs.
Better systems will send a small amount of power to front or rear axles (depending on which the main set of drive wheels are) upon acceleration, not just after slippage happens, to prevent loss of traction before it occurs.
These systems tend to be more intelligent as they can also vary the torque between front and rear axles, and possibly side-to-side depending on the manufacturer. However, they have no low range gearing.
Permanent AWD: These systems are fully automatic with no driver activation or intervention necessary.
The power sent to front and rear wheels is typically set at a fixed ratio (typically 50/50 or 40/60) so all wheels are powered at all times for neutral handling and all time traction before slippage occurs.
Being AWD, there is no low range gearing for off-roading.
Different manufacturers offerings
Mercedes Benz 4MATIC system: This is the generic name for Mercedes-Benz’s 4WD or AWD vehicles with four powered wheels.
It can refer to either a full-time AWD system, a permanent AWD system, or a Mercedes-Benz’s permanent 4WD system, depending on the model.
BMW xDrive: BMW’s permanent all-wheel-drive system that is typically rear wheel drive based.
This allows for the typical rear wheel drive sporty BMW feel that customers and owners expect.
This system is dynamic in nature and has the ability to transfer power fore and aft, side-to-side, and before slippage occurs.
The xDrive is available on over 20 different BMW models: from the BMW 3 Series Sedan, 4-series Coupé, to the BMW 5 and 7 Series Sedans, as well as their X3, X5 and X6 Sports Activity Vehicles including the BMW X5M and BMW X6M.
Subaru Symmetrical all-wheel drive: Subarus all use a permanent AWD system.
With over three decades of all-wheel-drive experience, including multiple wins in the World Rally Championships, Subaru has a lot of experience in this field.
Their dynamic system actively distributes engine torque to individual wheels in everyday driving, as well as in extreme conditions.
With a combination of equal length driveshafts and the boxer engine layout, Subaru’s claim to fame is that their system is better balanced and is more efficient than others on the market.
Audi Quattro system: This is perhaps the best branded permanent or full time all-wheel-drive system for passenger vehicles.
When people think of all-wheel-drive for passenger vehicles, Audi’s Quattro probably springs to mind. And as it should too, as Audi, partly as a way to win multiple World Rally Championships in the 1980’s, is largely responsible for popularising all wheel traction in cars that we can all enjoy these days.
These days there are several different types of Quattro systems varying on which vehicle you choose in Audi’s model range.
Honda Real Time 4WD: Honda’s part-time AWD system that is a bit of a misnomer as it does not have a low range gearbox.
This system only engages only when slippage occurs. The hydraulically actuated system is 100% front wheel drive until the wheels slip in which case the rear wheels receive power.
Overall system operation is completely automatic; no electronics or driver action is involved.
The greater the degree of front-wheel slippage, the greater the amount of torque fed to the rear wheels.
Mazda Active-Torque-Split AWD: Mazda’s full-time all-wheel-drive system that adjusts traction needs by monitoring wheel slippage, steering angle, yaw rate, lateral acceleration, and available driveline torque.
In normal driving, 100-percent of the driving torque is delivered to the front wheels.
During aggressive acceleration or when one front wheel is on the verge of slip, a controlled percentage of the available torque (up to 50%) can be directed to the rear axle.
The cost of adding 4WD or AWD system on a brand new vehicle ranges between $1,000 to $4,000 depending on the car model, system complexity and some specific features.
The difference in price on brand new vehicles between those with 4WD or AWD compared to those with 2WD is on average $3,000.00.
The same will be the case on the used vehicle models and hence it is old fashioned to just buy a vehicle because it has 4WD or AWD when you are not sure whether that system is of use to you or not.
*Stanley Makombe has 25 years’ experience in the motor industry, currently handling vehicle imports from Japan, Thailand, UK and South Africa into African countries. He is writing in his own capacity and can be contacted on +254 743 900 590, on X @Stan_Carsales, email: stanley@stanleymakombe.com, www.stanleymakombe.com
