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Is It Time For A Four-Wheel Drive?
written by Keith Sutton

Four-wheel-drive trucks have changed tremendously in recent years.
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Four-wheel drive
New 4x4s are more comfortable and have better feeling and responsiveness.

Not long ago, four-wheel-drive (4WD) vehicles were considered nothing more than specialty machines. Their exceptional performance in rugged backcountry and hard-to-reach jobsites made them the ideal choice for farmers, ranchers, hunters, fishermen and other outdoors-oriented individuals. But in the minds of the masses, the downsides of 4WDs often outweighed their advantages. Four-wheel drives were gas-guzzlers, prohibitively expensive, noisy, inconvenient to operate, uncomfortable to travel in and rough riding.  Not anymore.

     

Four-wheel-drive trucks have changed tremendously in recent years. You don't get the buckboard ride you once did. There's no whining or excessive noise. Lighter systems have improved fuel efficiency. Four-by-fours are more comfortable and have better feeling and responsiveness. And people are learning they have applications on the highway as well as in the backcountry.

     

Many people still purchase 4x4s for one primary reason: They can get you places a two-wheel drive vehicle can't.

     

A 4WD can take you to prime hunting and fishing areas away from improved roads better and quicker. Access to good lakes and hunting areas often is by unpaved roads and two-track trails that may be difficult to travel even in summer. Getting into these areas in a 2WD vehicle can be next to impossible, especially during the peak of hunting season when rain and snow are more likely to be falling. With a 4x4, though, you can get where you need to be, without as much worry about getting stuck or stranded. They're great, too, when you have to launch a boat on a slippery ramp or unpaved launch site. They're the vehicle of choice for most avid outdoorsmen.

     

Other people are joining the ranks of 4WD owners because of the advantages 4x4s offer in inclement weather conditions.

     

No vehicle can drive you safely on black ice. But in states that receive heavy amounts of snowfall, a 4WD is great for getting around on unplowed roadways. When snow is piled high, you need the extra ground clearance and traction of a 4x4. When it's raining, a vehicle with full-time 4WD drive is an asset.

     

Gone are many of the inconveniences once associated with 4WD vehicles. New and more sophisticated systems are featured on many. No more getting out in the mud to lock in the hubs. Just pull a lever or a switch, and you're in 4WD. Independent front suspension and rack-and-pinion steering make for smoother rides and better handling. Some systems control torque on each wheel independently. The mechanism looks for wheels that have traction and transfers the torque to those wheels to get you going quicker. Innovations such as these are making 4WD vehicles the right choice for more people.

     

There are several types of 4x4 systems, and you may find it useful to understand the variety available, along with some of their advantages and disadvantages. Here's a rundown:

 

Part-Time 4WD

     

This system, the most basic, operates after a driver either moves a shift lever or presses a button inside the vehicle. Otherwise, the part-time 4WD vehicle travels in 2WD mode. In recent years, automakers have been offering fewer vehicles with part-time systems, but some are still available.

     

If you try driving one of these vehicles on dry pavement with 4WD activated, you will likely feel an awkward, binding sense as you turn a corner. It's also possible to damage drive system components on these vehicles and cause premature tire wear if you travel in four-wheel drive on dry pavement.

     

This system is less complicated and less costly to build than some other systems, resulting in a lower vehicle price for car shoppers. And in rough off-road terrain, a driver can engage an extra-low gear for improved torque while in 4WD, another advantage. Part-time 4x4s also are durable under heavy stress.

     

Older vehicles with part-time four-wheel drive may require drivers to stop their vehicles before shifting from two-wheel drive to four-wheel drive. Some older vehicles also mandated that the driver get out and manually lock the front hubs at each of the front wheels. But most, if not all, of today's part-time 4WD vehicles are no longer built with manually-locking front hubs.

     

A disadvantage is that part-time four-wheel-drive systems make the driver responsible for deciding whether road conditions warrant engaging four-wheel drive. The driver also must decide when to deactivate four-wheel drive.

 

Permanent 4WD

     

The number of vehicles offered with permanent 4WD has remained steady in recent years. These systems, also known as full-time 4WD, have no 2WD mode. They always operate with power going to all four wheels, so drivers benefit all the time from four-wheel traction and don't have to shift or push a button to activate it. There also is no way to turn off the four-wheel drive. In rigorous off-road terrain, however, a driver can engage low range for improved torque.

      

Because drivers in vehicles with permanent 4WD don't need to activate the system, they can concentrate on driving, not judging road conditions and pushing buttons or shifting into four-wheel drive. There is no lag time for 4WD activation in these vehicles, as there could be in vehicles with automatic 4WD systems that engage only after sensing that road conditions have changed.

     

On the downside, vehicles with permanent 4WD can have less attractive fuel economy than you'd get from a comparable vehicle with part-time or automatic 4WD. And in some circumstances, driving with the center differential locked may make steering more strenuous because the vehicle will tend to want to travel straight forward, rather than turn.

 


Four-wheel drive is showing up in more vehicles each year.

Automatic or Full-Time 4WD

     

 Automatic, or full-time, 4WD has been a growing offering on vehicles. This system is designed to automatically decide for drivers when and where to apply torque to different wheels when added traction is needed. The driver engages a button on the dashboard, and the vehicle decides when to activate and deactivate 4WD, as necessary; the driver has no further input. A driver also can switch to low gear for improved torque in rigorous off-road terrain.

     

The appeal of these automatic four-wheel-drive vehicles is they monitor and sense their own traction needs as they travel, and automatically adjust how the power is delivered to the wheels. The driver can concentrate on driving, rather than having to decide whether to shift into four-wheel drive.

     

However, some 4WD experts say that in severe off-road conditions, the automatic system can hamper a driver's efforts. For example, because the system is quick and automatic, a driver may find the power shifting from one axle to another abrupt and unsettling while the vehicle attempts to climb over rocks or traverse a gulch. In this case, a driver should set the vehicle in 4WD high or 4WD low, rather than automatic 4WD.

 

The automatic system is more complex, typically with more components, than a part-time 4WD system, and it can be more costly.

 

All-Wheel Drive

     

All-wheel drive is showing up in more vehicles each year. It works like a permanent four-wheel-drive system by providing continuous power to front and rear axles. There is no way to turn off the all-wheel-drive feature, and a driver doesn't have to do anything to activate it. However, these vehicles can't be geared down to a low range for rigorous off-roading.

     

All-wheel-drive systems tend to be lighter and less bulky, and thus are suitable for use in a variety of smaller, lighter-weight vehicles such as cars and minivans. This also explains why all-wheel-drive vehicles don't necessarily have to be positioned higher above the road as 4WD vehicles are.

     

All-wheel-drive vehicles tend to offer respectable fuel economy compared with other types of 4WD vehicles. The systems also can be less pricey than those in vehicles with heavy-duty 4WD equipment.

     

The biggest drawback is the lack of a transfer gearbox that provides a low range to gear down the engine torque for the extra control that off-road enthusiasts often demand.

     

In the final analysis, there's no "best" drive-train layout. There are just different designs with different characteristics, and what's best is what's right for you. After reading this column, however, hopefully you'll have a better idea whether or not a four-wheel-drive vehicle is the right one for you, and if so, which type of system you'll need.

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