Four-Wheel Drive Hi vs. Four-Wheel Drive Lo

Jul. 19, 2016 By Tim Healey
When do you shift from 2WD to 4WD, and when you do when is it time for 4 Lo? Read along and we'll explore the topic.

If you have a four-wheel drive vehicle, particularly a part-time four-wheel drive vehicle as opposed to an all-wheel drive one, there’s a good chance it has two four-wheel drive modes: Four-wheel drive hi (or high) and four-wheel drive lo (or low).

While you might question why automakers are spelling it “hi” and “lo” instead of the more-accurate “high” and “low,” the better question is, what’s the difference? The next-best question is when do I need each mode, if my vehicle is so equipped?

On dry pavement, the answer is easy – you simply need to be in two-wheel drive. Even many dirt or gravel roads are safe to tackle in two-wheel drive. But off-road or during inclement weather, it’s slightly trickier.

As a short primer, let’s first look at the system most 4x4s employ. Most four-wheel-drive vehicles are fitted with a transfer case that allows the user to shift between two sets of gear – one high and one low. The lower gearing, which requires more revolutions of the engine to make one revolution at the wheels, essentially adds more torque to a 4x4 to scale obstacles or steep off-road trails.

Four-wheel drive hi, or 4 Hi, provides more traction when traveling at quicker speeds on loose and uneven terrain.

So when should you use hi or lo?

For snow, four-wheel hi is typically good enough to dig through the white stuff, and even at speeds above 25 mph on the highway it can offer additional traction. In general, four-wheel drive hi is better for off-roads speeds much faster than a crawl on surfaces that are too slippery for two-wheel drive. Four-wheel drive high can be helpful in gaining traction on hills and steep climbs, too. Same goes for mud. Although you can tackle rough dirt and gravel roads in two-wheel drive, sometimes it’s beneficial to switch to four hi to simply help smooth out the ride.

4x4 controls vary from vehicle to vehicle, as some employ levers while others have buttons and dials, such as this system found on the Jeep Cherokee.

Since four-wheel drive low adds torque through lower gearing, it can be useful for extremely steep hills, trails with loose rock or soft sand, rock crawling, and other off-road situations where a little extra torque is needed. That’s the main difference – you engage four-wheel drive lo in crawl-speed situations and/or in situations that present an extra degree of difficulty. Four lo helps reduce wheel spin, and that’s crucial to maintaining vehicle control when off of the pavement.
A couple notes here: If you can you select between two-wheel drive, four-wheel drive, and four-wheel drive lo, there’s a good chance you have a vehicle with part-time four-wheel drive. In order to avoid driveline bind-up, you should keep your vehicle in two-wheel drive on dry pavement. Full-time all-wheel drive systems, however, can be used on drive pavement (typically the vehicle’s computer chooses which wheels should receive the torque, anyway) and some of these systems do have a “lo” range that is safe to use on dry pavement. There are also vehicles that let you choose between two-wheel drive and all-wheel drive systems that are safe for use on pavement.

Climbing rock lined trails such as this is far simpler a task in 4 lo.

Hopefully that clears up when to use “hi” and “lo” with regards to four-wheel drive. Why automakers persist on using incorrect spelling, that’s harder to answer.

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