Four-wheel drive (4WD) has been a staple feature in off-road vehicles for years, but it wasn’t very common in other vehicle types in the past. Now, a lot of sports utility vehicles (SUVs) and crossovers come with 4WD or all-wheel drive (AWD) as standard. Most of these vehicles have systems that automatically distribute power to all wheels as needed. However, there are still some hardcore trucks and SUVs that have manual controls that allow drivers to choose when to engage four-wheel drive and whether it’s 4-high or 4-low. What do these settings mean and how do they work?
The 4-high and 4-low settings on your four-wheel drive vehicle do relatively different things and are calibrated for different road conditions. In general, these controls are connected to a manually adjustable drivetrain. Other settings are sometimes available such as 2-high and 4-high automatic. For now, let’s take a more in-depth look at the two more common base settings:
The 4-high setting is sometimes abbreviated as 4H or 4Hi on your drivetrain control panel. It locks the vehicle’s front and rear axles together. As a result, all four wheels are engaged and propelled forward at the same time while you drive. The transmission can shift gears from Low to High just as if you were driving down the road. The only difference is all four wheels are driving vs. just two. This helps prevent the loss of traction and also helps keep the wheels from slipping on more difficult terrains. If your system has a 4-wheel drive automatic system, you’re usually better off relying on that over the 4-high setting.
The 4-low setting is often abbreviated as 4L or 4Lo on the controls. Like the 4-high setting, 4-low also propels all four wheels forward at the same time. However, the 4-low setting makes it so the engine utilizes low-range gear ratios to optimize traction and power efficiency.
The 4-low setting is exactly the same as putting your transmission in first gear or low and driving. You can only go so fast before you feel like you’re driving up against a wall because the transmission cannot shift into 2nd gear. Putting a vehicle in 4-low mode is great because it prevents you from maybe accidentally accelerating too much and going too fast.
The 4-low mode is calibrated for driving on difficult terrain. Having the mode active lessens the strain on the clutch, engine, gearbox, and transfer case. The engine’s revolutions per minute in this mode are also higher due to the shorter gear ratios being utilized, which helps the vehicle utilize its existing torque better than other modes. This helps keep the engine from stalling even as your vehicle tackles steep inclines and declines.
If you aren’t sure whether you should be using the 4-wheel drive high vs. low setting, it’s best to familiarize yourself with what each mode does best.
The 4-high mode is great for driving at normal speeds over wet or snowy roads. It can also be helpful if you’re stuck in sand or snow. Keep in mind that you do need to limit your speed to under 55 mph to avoid damaging the transfer case though.
Alternatively, the 4-low mode helps you maximize your vehicle’s traction and power. It’s great for offroading situations like crossing creeks and crawling over rocks. That being said, the 4-low setting is calibrated specifically for these offroading situations and aren’t as suited for regular street driving unless you’re pulling heavy loads or going up a very steep incline. Your maximum speed when driving in this mode should ideally be 10 to 15 mph. So unless you’re a big off-road enthusiast, you likely won’t use this mode much.
Keep in mind that using four-wheel drive on dry or smooth roads can result in drivetrain damage. You’ll damage the drive train if you do any turns while driving on dry roads with the vehicle in four-wheel drive. Stopping is also more difficult, especially at high speeds. If your four-wheel drive vehicle has the option for two-wheel drive, it’s best to use that option instead for your daily drives. Alternatively, if an automatic mode is available, you can leave the switching up to your vehicle’s computer.
To put a vehicle into 4-low mode, you have to be stopped, put the transmission in neutral, place your foot on the brake, then shift to 4-low mode. You can shift to 4-high mode while driving.
I have had customers say that their vehicle will not go into 4-low mode, because they did not know they had to be stopped with the transmission in neutral.
–Anthony Harlin, ASE Certified Master Automobile Technician
How you switch modes will vary depending on the make and model of your vehicle. Older vehicles usually have a second lever beside the gear shift lever for switching into the various 4WD modes, but most modern vehicles just have buttons or a dial on the dashboard for the same purpose. Internally, switching between the four-wheel drive settings requires the use of a mechanical transfer case. The transfer case takes the engine torque that comes in from the transmission and splits it, sending the torque either to only the rear wheels or to all four wheels depending on the mode you choose. This applies when switching between 2-wheel and 4-wheel drive settings.
While many modern four-wheel drive vehicles are outfitted with an automatic mode, there are still a host of older offroaders that give you, the driver, the option of changing between the modes manually. This offers more control, but it also means you’re responsible for understanding where and when to use the right modes. Now that you’ve familiarized yourself with the differences between 4-wheel high vs. low modes, you’re off to a good start.
When it comes to vehicles with a 4-wheel-drive system, it’s important to make sure critical parts like the differentials and the transfer case are working properly. Damaged or malfunctioning parts must be checked by a professional and replaced as needed.
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