In principle, four-wheel drive is a pretty simple concept. Power from the engine is sent through the transmission to a transfer case that sends power to the front and rear wheels.
In the last couple years, traction control, antilock brakes and stability control programs have become integrated into modern four-wheel drive vehicles, vastly improving their capability.
Instead of a traditional transfer case that you engage with a lever, many modern 4x4s allow the driver to tailor the driving experience with the push of a button or the turn of a dial.
Niecie’s Renegade, for example, features the company’s Selec-Terrain system. This dial allows the driver to cycle through several driving modes to enable the vehicle to tackle a wider variety of obstacles ranging from sand and snow to rocks and mud.
When the Renegade is shifted into rock mode, the four-wheel drive system locks into low range, disables electronic stability control and adjusts the throttle response for improved control.
Land Rover’s Terrain Response system works the same way. The driving modes may have different names, but the idea is the same to make driving on or off-road a lot easier.
In my mind, it also makes the vehicle a whole lot safer. These systems allow the driver to worry about where they are going and getting there safely.
Today, manufacturers are doing their best to take the human element out of their 4×4 systems.
In Jeep’s Selec-Terrain, “Auto” delivers power to the wheels that need grip. On high grip surfaces the Jeep can perform like a traditional part-time 4×4 sending power to just two wheels.
If the front wheels lose grip or the driver accelerates suddenly, power is automatically delivered to the rear wheels. Once the extra traction is no longer needed, the vehicle will automatically return to two-wheel drive for improved fuel savings.
These computer-controlled 4×4 systems have significant advantages over traditional part-time drives, in particular for those who want to stay on the road rather than go venturing off it.
The old school
For those heading off the tarmac into part’s unknown, part-time four-wheel drive is still king.
In a traditional part-time four-wheel drive vehicle, a gear or chain driven transfer case evenly splits power between the front and rear tires. When engaged, the front wheels will spin at the same speed as the back no matter what surface you’re going over.
Part-time 4x4s are ideal for off-road applications because if a rear wheels slip the front wheels will keep pulling the vehicle forward.
Jeep’s Command Trac and Rock Trac systems are prime examples of part-time four-wheel drive systems.
However, these systems have few drawbacks. One of the largest limitations is they can’t be engaged on dry, high grip surfaces, i.e., pavement.
Capability vs. Safety
Part-time four-wheel drive’s limitations introduce another argument regarding safety. For many customers, four-wheel drive has become analogous with safety. They don’t buy a 4×4 because they never intend to go off-road; they’re getting it because they have to get to work in a blizzard a few times a year.
Here, modern 4x4s are the clear winners. If the driver doesn’t have to decide when to enable four-wheel drive, they can focus more time and energy on where they are going, and this makes driving safer.
It also means the car doesn’t have to stay in four-wheel drive any longer than it needs to be. This is actually how Niecie’s Renegade works when the Selec-Terrain system is left in “Auto.”
Unfortunately, these so-called “slip-n-grip” 4×4 systems aren’t so great when you start to venture off the pavement and into the rough stuff.
Manufacturers have attempted to get around this dilemma with the use of computers which help to make up for the compromises made to improve the vehicle’s on-road performance.
No right answer
Neither 4×4 system is perfect. 4x4s have long been the Swiss army knives of the automotive world, jack of all trades master of none.
Off-road, old-school 4x4s like the Jeep Wrangler or the Land Rover Defender are unmatched, but to achieve this level of capability, huge compromises have to be made to their on-road performance.
Modern 4x4s aim to provide better on-road handling at the cost of off-road performance. Manufacturers make up for these compromises with fine-tuned computer-controlled terrain management systems that direct power to the wheel that needs it most, and for the most part it works beautifully.
At the end of the day, it comes down to how you’re going to use your vehicle most. If you rarely venture onto anything more challenging than a rutted-out fire road, a modern 4×4 is going to suit you best. It’ll offer you civilized handling on the pavement and plenty of capability off it if you know its limits.
If you’re one to push the limits or you just want a vehicle that can go anywhere no matter how challenging, an old-school 4×4 will probably suit you best.advertisement
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