Today’s 4WDs are full of high-tech features, buttons, and accessories and for prospective 4WD owners, it can be a little confusing trying to decipher all the marketing jargon. One source of confusion arises between the concepts of part-time and full-time 4WDs and how the technologies used in both types of vehicles differ. The problem is, there are no strict definitions or specifications and a variety of technologies are used to power all four wheels. At the end of the day, a 4WDs classification as either a part-time or full-time 4WD is largely determined by the manufacturer.
If you’re interested in buying a 4WD then it’s vital to understand the basic difference between part-time and full-time 4WDs to ensure the vehicle can meet your individual requirements. To guide you in the right direction, today we’ll be comparing the two types of vehicles to give you a better understanding of how they fundamentally differ so you can choose the right vehicle for your needs.
In the early days, almost all 4WDs were based on the part time system whereby the rear wheels were powered by a conventional transmission and differential in a similar fashion to how a 2WD is operated. To engage 4WD, the driver needed to get out of the vehicle and turn the locking hubs on the front wheels by engaging the transfer case which then deliversidentical power via a front differential to the two front wheels. The transfer case is also used to change between low-range and high-range 4WD so it essentially has three different configurations – high-range 2WD, high-range 4WD, and low-range 4WD.
The idea behind the part-time system is to reduce the moving parts in the front of the vehicle which allows the driver to save fuel as powering four wheels naturally consumes more fuel than powering just two. Modern part-time 4WDs sold today have a range of features including traction control, descent control, anti-lock braking, along with a multitude of other attributes (such as steering dampers) which helps drivers traverse rough terrain. Instead of engaging the transfer case and using a second gear stick to operate 4WD, modern part-time 4WDs have buttons which does this automatically.
It’s important to note that part-time 4WDs can only operate as a 4WD when off-road and never when driving on sealed roads. Every vehicle requires all four wheels to rotate at different speeds when turning (outside wheels slower than inside wheels, rear wheels slower than front wheels), and driving with all four wheels spinning at the same ratecauses transmission wind-up which can lead to serious drive-train damage.
To meet the demand of buyers looking for a safer, more user-friendly 4WD, manufacturers decided to release the full-time 4WD concept. Many part-time 4WDs required the driver to stop the vehicle to lock the front hubs and thus engage 4WD which is a little inconvenient considering that these vehicles have high-tech gadgets and accessories such as heated seats and entertainment systems. For most buyers though, the idea of using 4WD on the highways was the most appealing aspectto improve the vehicle’s traction, handling, and cornering.
As stated earlier, the only problemin using 4WD on the highway is transmission wind-upso to overcome this issue, a differential was installed between the front and rear differentials which allows each wheel to receive 25% of the torque from the engine. Essentially, the centre differential allows ‘slippage’ between the front and rear wheels and the front and rear differential allows slippage between their respective wheels. When traveling over rough terrain, the driver simply locks the centre differential (using a button or lever) which enables the car to act as a true 4WD by delivering equal torque to both the front and rear wheels of the vehicle.
Of course, full-time 4WDs also have the ability to switch between low-range and high-range 4WD for improved off-road ability, however unlike part-time 4WDs, there is no 2WD drive option. Full-time 4WDs can be operated in high-range 4WD, ‘locked’ high-range 4WD, and ‘locked’ low-range 4WD. It’s important to remember thatfull-time 4WDs can never be driven on the bitumen with the centre differential locked as it will cause transmission wind-up and damage the drive-train.
Which type of vehicle is better?
The type of vehicle which is better for you really boils down to your personal preferences and driving needs. While modern part-time 4WDs have a button to lock the front hubs which saves you the hassle of getting out of your vehicle, full-time 4WDs are generally viewed as safer because of the improved handling and traction. If you don’t travel off-road often and wish to save money on fuel, then a part-time 4WD might be best for you. On the other hand, if you spend most of your time off-road then a full-time 4WD may be the best alternative.
In any case, having an understanding of how these two types of vehicles differ is the first step in choosing the right vehicle for you!
If you have any further questions about part-time or full-time 4WDs, simply reach out to the experienced team at TJM Australia. For more information, phone our head office directly on 07 3865 9999.