The four wheel drive started out as a military technology that allowed machines of war to wander off road and to go over any obstacles. A vehicle’s four wheel drive system is almost similar to normal vehicles except that the transmission and drivetrain are designed for stability rather than fast driving, most of the time. Moreover, most four wheel drive vehicles have higher suspension systems or even a user selectable height adjuster which lets the driver adjust ground clearance according to road or off-road conditions.
To start driving 4x4 first engage the 4WD system on your SUV or truck. Some have this as a shifter or lever on the dash or center console. The transmission will then engage all four wheels, rather than just the rear wheels for traction.
Some vehicles have automatic selectors or manual front wheels, which can easily be seen on the wheel hubs. If you see selectors that have a knob in the middle with two positions marked, that means you have a manual select four wheel drive vehicle. This type requires the driver to get out of the vehicle, change the wheels settings to four or two wheel drive.
Be careful with the clutch and accelerator for they will be more responsive and sensitive in four wheel drive as compared to when only the rear wheels are engaged. The slightest push on the gas would result in the vehicle suddenly moving, depending on the gear. The high suspension allows you to clear rocks and other obstacles easily. Generally, four wheel drive trucks and SUVs are quite wider, so they are more stable when on rough roads and when traversing muddy and rocky terrain.
In more high end SUVs and trucks, the driver can usually adjust seat height. Having a higher position might help shield one from the bumps and jars of off-road driving. You also have a high vantage point, and so you can more easily spot possible obstacles.
In 4WD trucks and SUVs, speed can be dangerous when traversing off-road conditions. High speed is not advisable, as you run the risk of damaging your drivetrain and transmission if you speed past 50 mph while on fifth gear.
Lastly, when you return to the pavement, remember to disengage the four wheel drive system. This will prevent a lot of trouble and cost in potential repairs. Leaving it at 4WD would put undue stress on the gearbox, crankshaft, transmission, differential and gearboxes. The only exception is trucks and SUVs where you can select the “fast” 4WD option, which lets the vehicle run on the road, with all four wheels engaged to the drivetrain. Driving on smooth roads while on 4WD will also consume more fuel.
Some cars and small SUVs have 4WD systems that are automatically engaged, or are always on standby. These are called “all wheel drive.” These vehicles are not usually true 4WD in the strictest sense of the word, but the all wheel drive functionality is designed to help against skid and loss of traction in slippery roads and wet weather, rather than off-roading.