Hobbies Cars & Motorcycles Uses of the Popular 4WD Share PINTEREST Email Print PeopleImages/Getty Images Cars & Motorcycles ATVs & Off Road Cars Motorcycles Used Cars SUVs Trucks Public Transportation By Jim Walczak Jim Walczak is a Jeep and off-roading enthusiast and the publisher of "Fun Times Guide: Jeep Guide." our editorial process Jim Walczak Updated June 11, 2018 The first digit in a "wheel-drive" equation refers to the number of wheels. The second digit refers to the number of driven wheels. 4x4 (four by four): A vehicle with four wheels that's powered by four wheels (4WD)4x2 (four by two): A vehicle with four wheels that's powered by two wheels (2WD) Today's vehicles offer a number of different drive train systems designed to help out in slippery conditions. For example, a four-wheel drive vehicle may come equipped with "Full-time 4WD", "Part-time 4WD", or "Automatic 4WD". 4WD Modes Here's what you should know about each, and when you should actually drive in 4WD mode. In general, 4-wheel drive refers to a vehicle's drive train system that can send power to all four wheels, but the four wheels are not necessarily under power all at the same time. Here's an explanation of the different types of four-wheel drive systems: Full-time 4WD (or permanent 4WD) means the vehicle is constantly providing power to all four wheels, usually with power being shifted between the front and rear axles as needed. This provides maximum traction in both dry and slippery driving conditions and requires no action from the driver to activate it. IMPORTANT: Full-time 4WD doesn't provide as much mobility off-road as part-time 4WD does, because the system is designed such that it allows a set of wheels (front or rear) to spin if they don't have traction.Part-time 4WD refers to a vehicle with selectable 4x4 or 4x2, requiring the driver to manually shift between 2WD and 4WD using either a lever or a switch. With part-time 4WD, you can "shift on the fly" (switch between 2WD and 4WD while driving). Part-time 4WD gives you better traction on slippery surfaces because the front and rear sets of wheels are locked together. Thus, this is the optimum choice for most off-road conditions. IMPORTANT: Vehicles with part-time 4WD systems should not be driven on dry, smooth road surfaces when in 4WD mode, or you will soon be spending a lot of money on repairs.Automatic 4WD is a full-time system that lets the vehicle operate in 2WD (either front or rear) until the system judges that 4WD or AWD is needed. It then automatically routes power to all four wheels, varying the ratio between front and rear axles as necessary. Usually, a slipping wheel activates the system. However, some of the more sophisticated systems use software that switches the system to 4WD or AWD during specific driving conditions — BEFORE a wheel begins to slip. IMPORTANT: Automatic 4WD vehicles are not recommended for serious off-road driving because all four wheels are powered at all times, which is not wise under certain off-road conditions. To determine which type of four-wheel drive your vehicle has, consult your owner's manual. There you should also find additional information with regard to driving your vehicle in 4WD mode. The gearing options found in 4WD vehicles help a vehicle tackle many of the unique situations encountered while driving off-road. Following are a variety of conditions in which you would want to use 4WD to avoid sliding or spinning. Hi Range 4WD 4H allows you to drive full speed, if necessary. The high range ratios in 4WD mode are the same as the gear ratios in 2WD. Here is when to use 4H: for traction when the area isn't steepwhen stuck in the sandextremely slippery conditionssnowicerocky, gravel roadsgulliesextremely muddy areasridges Low Range 4WD 4L is for creeping along at slow speeds. It reduces the strain on your vehicle, just remember to stay below 25mph in low range. While it does not provide more traction, it does provide 2-3 times more torque at about 1/2 or 1/3 of the speeds in high range. Low range gear ratios are approximately half that of high range. Here is when to use 4L: on wet, slippery surfacespassing through sandy areason rough trailsthrough shallow waterrock-climbingclimbing steep hillsthrough muddescending steep hills Additional Tips Don't change gears in the middle of a water crossing, going up or down hills, or in sand dunes.Be prepared: Engage low-range 4WD before you need it.Don't operate 4WD on hard dry surfaces.When in doubt, use a lower gear!