So you recently purchased a 4WD vehicle, and you suddenly see these strange buttons, knobs and levers with what looks like Greek lettering. Things like 4Hi, 4Hi L, 4WD Low L, differential lock, traction control, and so on. More recent models will even have things like terrain management or response. This can get so overwhelming that you might end up not using them altogether.
Don’t blame the poor sales person who sold you the vehicle, because in all probability they don’t know how to properly use them either. So here is a brief guide on how to properly engage for the right conditions.
* 2WD. On most 4WD vehicles, this is the normal mode you’d use for everyday driving conditions.
* 4Hi L. Please note that “L” means the vehicle’s center differential is locked, meaning the front and rear axles spin at the same speed. This is usually used on sand, wet grass, and firm muddy surfaces. All these conditions must have little or no incline.
* 4WD Low L. This mode actually slows the vehicle’s speed but increases torque, or the twisting motion that's applied to the wheels and tires. The slow speed gives the tires a chance to bite on the driving surface. This is used on muddy surfaces. It is also used for rough, rocky surfaces for better control of the vehicle due to its slower speed, thus giving crawling capabilities over rocks and bumps.
Recent 4WD technology has added electronic off-road driving aids to take the witchcraft out of the process. Even so, it’s important that the driver understands the physics involved in off-road driving to maximize the use of these aids.
* ETC (electronic traction control), VSC (vehicle stability control), DSC (dynamic stability control). Whatever your preferred carmaker wishes to call this feature, it’s all the same and usually all modern vehicles are equipped with this. This mode prevents any vehicle from slipping and sliding uncontrollably on slippery surfaces.
When off-road vehicles face a steep incline, these features impede forward progress once the vehicle slips to one side by cutting engine power and applying the brakes automatically. The deal here is to shut these driver aids off before going off-road. On some vehicles, these features are automatically disabled once yous witch to 4WD Low.
* Differential lock. This feature is beginning to appear on 4WD vehicles and must only be used in very difficult off-road conditions. It is usually installed on the rear axle of most production vehicles for safety reasons. A few models are equipped with this on the front axles, namely the Mercedes-Benz G-Class and the Jeep Wrangler Rubicon. Special training is required to operate this front differential lock for off-road conditions to operate the vehicle safely. What it does is activate the right and left wheels at the same time to get maximum traction.
* 4Hi. Note that there’s no “L” on this mode. This applies to vehicles equipped with a center differential, like the previous generation Toyota Fortuner, Land Rover Defender, and late-model Mitsubishi 4WDs. It’s used on hard but fairly flat driving surfaces with water or sand.
* Stabilizer bar disconnect. This mode disconnects the vehicle's stabilizer bar from the suspension to allow more travel. This way, the suspension can follow uneven surfaces and keep the wheels on the ground. This is not a very common feature and is only used off-road.
Different brands have different features and it is impossible to explain more, so learn how to efficiently and safely use these features. If you own a 4WD vehicle, it is recommended to sign up for a proper and certified off-road driving program.