When it comes to traction on slick pavement, gravel roads, snow or off-road, four-wheel drive may be more likely to help keep you moving forward when a two-wheel drive vehicle could slip off the shoulder or be buried up to the axle attempting to get a grip. This begs the question: When do you use the various modes of four-wheel drive?
Here’s the down and dirty, which will help keep you from having to dig a stuck truck out of a ditch.
In high-range four-wheel drive, you can travel at all normal speeds. Engage this setting when you’re on the highway and roads are sketchy – wet, snowy, icy. It’s also good for level, loose-gravel roads, packed sand or mud. Simply put, 4H is used for driving at normal speeds when you need extra traction, according to Popular Mechanics.
The low-range four-wheel-drive setting is for the serious stuff – deep sand, snow, mud, crossing water, climbing rocks and ascending/descending hills. When you use four-low, keep your speeds low, too (under 40 mph or so), as you’re not actually gripping the road any better but you’re applying more torque to that grip. Designed for maximum traction and maximum power, the wheels will turn more slowly in 4L than 4H, says Popular Mechanics.
This is a modern convenience that allows you to effectively “set it and forget it.” In this setting, the vehicle monitors tire traction while in two-wheel drive and automatically shifts into four-wheel drive when one of them begins to slip. Use this setting when roads are variable, such as patchy snow and ice or any other combination of conditions when a tire could slip suddenly. There are two types of AWD: part-time or automatic AWD, as mentioned above; and full-time AWD, which delivers power to all four wheels but lacks the low-range torque found in 4L, according to Edmunds.
You should never travel in four-wheel drive on flat, smooth, dry roads, as it will damage your drivetrain. Also, remember that four-wheel drive provides more torque and engages all the tires for movement – it doesn’t help you stop. Always travel at speeds that allow you to stop safely, regardless of how well you’re moving forward.
When shifting from two-wheel drive to automatic four-wheel drive or four-high, you can do so “on the fly” – or while traveling at normal speeds. When shifting into and out of four-wheel-drive low, however, you will likely need to come to a stop and wait for the indicator light to stop flashing.