If you’re driving a vehicle that can switch between 2WD and 4WD modes, what happens if you accidentally (or deliberately) get on the highway when in 4WD mode? Is that in any way dangerous? Or is driving in 4WD mode on a highway safe?
The short answer is: Yes, it can be safe to drive in 4WD on the highway as long as you’re going very slowly and so does the rest of the traffic around you. In other words, only during severe road conditions that require you to.
To understand why, we need to recap some of the info we covered in the post about when to use 4WD and what this system is even good for, other than the very obvious case of off-roading adventures.
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Not sure which system you have?
Four-wheel-drive systems are offered in many configurations such as part-time, full time, manual shift, on-the-fly shifting, and fully automatic. Each four-wheel-drive system has its own requirements for how you engage and disengage it and when you can operate the vehicle in 4WD mode. If you’re unsure which four-wheel drive system you have, ask a dealer, who can figure it out from your VIN.
4WD can be dangerous
- 4WD doesn’t improve handling on slick ice- and snow-covered roads. If you drive faster than conditions allow, you’re far more likely to flip and roll because of your higher centre of gravity.
- 4WD doesn’t help you brake better or give you more stability in turns while braking. So slow down when you’re turning and brake sooner.
- 4WD contributes to overconfidence. Guess which vehicles end up in the ditch more often?
Don’t waste gas
When you’re in 4WD, you’re spinning a lot more heavy metal. Getting those extra gears and drive shafts up to speed and keeping them spinning takes extra energy, which lowers your gas mileage. If you don’t need 4WD, turn it off and save some dough at the gas pump.
If you get stuck
Resist the temptation to shift between forward and reverse to rock yourself out of a rut. Instead, shift into 4HI and slowly feather the gas pedal to inch your way out. Don’t spin your wheels. If that doesn’t work, rock the vehicle back and forth by applying and releasing the gas.
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Don’t destroy your drivetrain
Driving a part-time 4WD system on dry pavement can break the front axles, shear the differential gears and even break apart the differential case. As soon as you hit dry pavement, shift back into 2WD.
4WD vs. AWD: What’s the Difference?
In two-wheel-drive mode, the system delivers all the engine torque to the rear differential, so each rear wheel receives 50 per cent of the available engine torque. In 4WD mode, each wheel receives 25 per cent of the available engine torque. Older 4WD systems must be manually shifted between 2WD and 4WD and from 4HI to 4LO while the vehicle is stopped. Newer s 4 wheel drive systems have electronic push button ‘on the fly’ features that let you shift while driving.
An AWD car can deliver all engine torque to all four wheels all the time. But some AWD systems deliver all engine torque to the front differential until the system detects wheel slip. Then it transfers a varying degree of engine torque (0 to 100 per cent) to the rear wheels. So it’s a 2WD system most of the time. Other AWD systems work differently; they split the engine torque 50/50 between the front and the rear differentials at all times unless they detect wheel slip. Then they ‘reapportion’ the torque between the front and the back differentials based on need.
Know how to engage and disengage your 4WD
Some older and more basic 4WD systems must be engaged manually with the vehicle at a complete stop and the transmission in either Park or Neutral. Don’t try to engage these four-wheel-drive systems when the vehicle is moving, or you can damage expensive components. However, most 4WD systems can now be shifted into or out of 4WD on the fly at the push of a button. The most sophisticated 4WD systems are fully automatic. They shift into and out of 4WD automatically as the system detects the need for more traction.
Knowing when to use 4HI or 4LO is what causes the most confusion for 4WD vehicle owners, so here are some rules.
When to Use 4WD?
Use 4WD in the following situations:
- When you need additional torque/power, such as pulling heavy loads at slow speeds.
- When you are descending at slow speeds while hauling a heavy load.
- When you are going over steep inclines and declines, such as rocky situations.
- When you are stuck in snow, mud, or sand; however, stop immediately if your wheels are spinning and follow the advice in this article.
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Four-Wheel Drive Advantages
The main benefits of 4WD are traction and power. Have you ever seen those commercials where the Jeep is climbing over boulders and rocks? That’s 4WD in action.
If you are climbing a steep hill or are off-roading, you will want increased power in order to get over obstacles and climb steep hills. While 2WD will get you over even the steepest hills of San Francisco, if you are off-roading, you will probably want the extra power that comes with 4WD.
- 4WD improves traction in dangerous driving conditions, such as snow, ice, rocks, and other scenarios that can make control difficult. By engaging both sets of wheels, traction, and control improves.
- The additional weight contributes to a better grip on the road.
- 4WD is great for those who like off-roading.
If you frequently drive in conditions where there is low traction, or if you enjoy off-roading, you will greatly benefit from four-wheel drive.
Four-Wheel Drive Disadvantages
In most cases, 4WD is not necessary. It uses more fuel and can also lead to overconfidence, leading to more situations where you can get stuck. Save money and fuel by only using 4WD when you need it.
- The main disadvantage of 4WD is added cost for purchase, maintenance, and fuel. The extra equipment (differentials, transfer case, etc.) adds complexity and weight to the vehicle, increasing initial market value, tire wear, and the cost of repairs and maintenance.
- The added power and weight of 4WD and AWD systems require more fuel, making them less efficient than their 2WD counterparts.
- Added weight improves traction and control, but it also increases the braking distance required to make a complete stop. Lighter vehicles can avoid collision easier than heavier vehicles.
- 4WD and AWD can cause overconfidence in drivers, ironically leading to more situations where you can become stuck.
- Although 4WD improves traction, slow down and use extreme caution on icy, snowy, and slick roads. Overconfidence can lead to dangerous accidents.
4WD Tips and Tricks
- 4WD vehicles work best when they are regularly used and maintained according to manufacturer recommendations. If you don’t use the 4WD system for extended periods of time, the seals can dry out. It’s best to keep the system lubricated by activating it at least once every few months.
- Only use 4WD when you need it to save as much gas and money as possible. Driving 4WD on mild, dry conditions can do damage to your front axles, differential gears, and other parts. Always use 2WD on dry pavement.
- If you get stuck, switch to 4WD and slowly depress the gas pedal to get yourself out. If the wheels start spinning, stop before you dig yourself a deeper hole.
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 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.
Automatic Four-Wheel Drive (AWD)
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 the 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.
Keep in Mind
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 travelling 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.
When shifting from two-wheel drive to automatic four-wheel drive or four-high, you can do so while continuing to travel at normal speeds. When shifting into and out of a four-wheel-drive low, however, it is best practice to come to a stop and wait for the indicator light to stop flashing.
When to use 4H and 4L
Knowing when to use 4H or 4L is what causes the most confusion for 4WD vehicle owners, so here are some rules.
When to Use 4L:
- When you need more torque (power) for heavy pulling at slow speeds.
- When you’re climbing steep grades at slow speeds and need extra power.
- When you’re descending steep hills with a heavy load-the low gearing provides engine braking assistance.
- Don’t use 4LO to get unstuck in mud and snow. The extra torque will cause the tires to spin.
When to Use 4H:
- When you’re on slippery surfaces and driving at street or highway speeds.
- When you’re stuck in snow, mud or ice.
How to use traction/stability
Most new cars and trucks have a traction/stability control feature. The system automatically turns on every time you start your vehicle. When the traction/stability control system detects wheel slip or vehicle instability, it immediately tries to compensate by cutting engine power, braking the slipping wheel or braking other wheels to force the vehicle back into its intended path. It works great when you’re travelling along the road and hit a slick spot. But when you’re stuck, traction/stability control can work against you, making it harder to get out of a rut in snow, mud or ice.
So when you get stuck, turn off your vehicle’s traction/stability control. The procedure is different for each vehicle, so refer to your owner’s manual. Depending on the vehicle, the traction/stability control may turn itself on again after a set period or after an engine restart. You may have to turn it off repeatedly if you’re stuck for an extended period.
4 WD – Use it or lose it
4 WD systems work best and last longest when they’re used regularly and maintained according to factory recommendations. When a 4WD system sits unused for months at a time, the linkage and hub components seize, the seals dry out, and the lube drains off gears. The best way to keep all 4WD components lubricated and in good operating condition is to engage your 4WD at least once every few months on wet pavement (preferably in a secluded parking lot) while performing a few figure eights.
Next, follow your owner’s manual for differential and transfer case fluid changes even if you don’t use your 4WD very often. And grease drive-shaft slip joints and U-joints (where possible).
Tire size & tire rotation are critical
The front, centre and rear differentials in 4WD vehicles are designed to compensate for short-term differences in wheel speeds encountered when turning a corner or changing lanes. But mismatched tires, whether they’re a different size or a different tread depth, force the differentials to operate full time even if you’re going straight down the road. That constant operation creates excessive heat and causes premature wear that can cost thousands in unnecessary repair bills. A difference in tread depth of just 1/16 in. among tires is enough to cause early failure.
Front tires wear faster than rear tires because they carry more weight, perform more braking and turn the vehicle. So rotating your tires every 5,000 to 7,000 miles is critical to spreading the wear evenly and minimizing differential operation. If a tire is wearing unevenly, exceeding the 1/16-in. threshold, you’ll have to buy four new tires or shave down the new tire to match the tread depth of the others.
Finally, different tread brands, tread patterns and even different rubber compounds can result in different traction rates between the tires, and that stresses 4WD components. So avoid mixing different brands or tread patterns on your 4WD vehicle.
Which 4WD Gear To Use When Driving On The Highway?
Be sure to set your truck or SUV to 4H four-wheel drive. This way, you can drive at normal speeds when on the road. Remember, 4L simply means using lower gears in 4WD mode. If you try to use 4L while driving in highway speeds, you’re going to reach high RPMs without gaining much speed. That’s not good for your vehicle at all.
Using 4H, you’ll get all the traction you need so you can safely reach your destination at a reasonable speed. There’s no need to ever use 4L four-wheel drive for highway driving.
Also, in most vehicles, if you’re already on the road and the conditions suddenly change, you can switch to 4H four-wheel drive while you’re driving. This is not the case with 4L four-wheel drive when you must slow down significantly or even stop.
4WD increases your traction. That’s important when the road doesn’t provide enough friction (as in the case with snow, ice or water on the road). It’s also relevant when you’re moving a heavyweight on a steep grade. 4WD can add some more traction and help you fight against gravity.
That’s when you need to.
Technically, you could drive in 4WD on any paved road, but the problem is that you’ll be locking the differential ration between your wheels. That can be dangerous when you’re trying to turn the vehicle and need the wheels on either side to move at different speeds.
So, driving in 4WD should be done slowly and only when road conditions require it.
Driving In 4 Wheel Drive On Highway: Can You and Is It Safe?
4WD increases your traction. That’s important in the case of snowy, icy or wet roads, or when you’re moving a heavyweight on a steep grade. These are the instances when you need to engage 4WD.
Although technically, you could drive in 4WD on any paved road, 4WD is generally not an ideal mode to use while driving on dry, flat, level roads. The problem here is that you’ll be locking the differential between your wheels, so all four wheels will be turning at the same speed.
That is very dangerous when you’re moving at high speed on the highway and trying to turn. Turning requires the wheels on either side to move at different speeds: the outer wheels have to cover a longer distance, thus will have to rotate faster.
So, driving in 4 wheel drive on the highway: can you? Yes, technically you can use 4WD on the highway, but if you do, make sure it’s 4H four-wheel drive. Using 4H, you’ll get all the traction you need so you can safely reach your destination at a reasonable speed.
Do not ever use 4L four-wheel drive while driving at highway speeds. Remember that 4L simply means using lower gears in 4WD mode. If you try to use 4L, you’re going to reach high RPMs without gaining much speed, which is not good for your vehicle at all.
Also, in most vehicles, if you’re already on the road at a certain speed and the conditions suddenly change, you can switch to 4H four-wheel drive while maintaining your speed. Meanwhile, with 4L four-wheel drive, when you must slow down significantly or even stop.
In short, while you can use a four-wheel drive in inclement weather for highway driving, you should not use it in good weather conditions. In addition, when you do need to engage four-wheel drive on highways, make sure it’s 4H setting.
As mentioned above, driving in 4 wheel drive on highways at high speed is only safe on straight routes. Any turning at high speeds could be extremely dangerous.