Four Wheel Drive How-to
By Wayne Scraba/autoMedia.com
Get to Know Your Four-Wheel Drive Vehicle -
Plenty of folks buy a 4X4 pickup truck or SUV and never intend to take it off-road. In fact, plenty of those same folks never even think about actually using the vehicle's capabilities to its fullest. They simply want the peace of mind that comes with the fact they can switch from two-wheel drive (2WD) to four-wheel drive (4WD) with either the tug of a lever or (even more common today) the turn of a switch. If you're in that same group, have you ever wondered what the controls for the 4WD system actually do? And, equally important, when and where you should use them? If so, you're not alone.
|Here's a 4WD how-to to help you get to know your four-wheel-drive vehicle:|
here are several different types of 4WD systems. The two most common include full-time 4WD and part-time 4WD.
There are also certain automatic 4WD systems offered that allow the vehicle to operate in 2WD until the system senses a need for 4WD, or all-wheel drive (AWD). The system automatically routes the power delivery to all four wheels, varying the amount of power provided to the respective axles as necessary. Most often, a sensor is triggered by a slipping wheel, which, in turn, engages the 4WD. Keep in mind that some of these systems are not designed for serious off-roading (usually in vehicles where the front axle does the principle amount of work). On the other hand, applications—such as those found under some pickup trucks where the rear axle does the principle amount of work in 2WD—are more than off-road capable.
- Full-Time 4WD means the vehicle is always making power available to all four wheels, typically shifting the power from the front and rear axles as necessary. Full-time 4WD offers maximum traction under all conditions, and does not require additional input from the driver (to turn on or off). Due to the nature of a full-time 4WD system, you'll find the vehicle does not have the overall on-road mobility of a part time 4X4 package.
- Part-Time 4WD means the vehicle has a means to select between 4WD and 2WD. It could be a lever or it could a switch. With this setup, you shift between 4WD and 2WD on the go. A vehicle with part-time 4WD provides superior traction on slippery surfaces because the front and rear sets of wheels are (obviously) locked together. It's important to note that vehicles with part-time 4WD systems should not be driven on dry, smooth road surfaces when in 4WD mode. The constant use of 4WD under these conditions can damage drivetrain components.
Your owner's manual will explain what type of 4WD system your vehicle is equipped with. Most manufacturers offer detailed information on where and when to use 4WD. Nonetheless, here is a synopsis of where and when to engage the system:
4-High allows you to drive full speed, if necessary (keeping in mind the caveat mentioned earlier regarding driving on dry pavement). The high-range ratios in 4WD mode are the same gear ratios as the vehicle has in 2WD mode.
When to use 4-High: Additional traction when the terrain isn't steep; snow; ice; muddy roads or when operating where there is no road; rocky, gravel roads; when stuck in sand or snow; under extremely slippery conditions.
4-Low alters the gearing in your vehicle. It is designed so you can creep along at slow speeds (which also reduces the potential for damage to your vehicle). Most manufacturers recommend you do not exceed 45 mph in 4-Low. Keep in mind that 4-Low does not provide more traction. Instead, it provides considerably more torque (often 2-3 times that of 4-High at very low speeds).
When to use 4-Low: On wet, slippery surfaces; in heavy, wet snow; climbing or descending steep hills; on very rough terrain (trails, off road); powering through mud; climbing rocks; driving through deep sand; fording water.