If you would like to find out how the dynamics of a 4 wheel drive works and if it helps in the rain, this article is for you. Four-wheel drives offer many advantages over 2WD and even AWD vehicles, but does this superior traction give drivers a false sense of confidence when roads are wet? We will look at how the drivetrain of a 4WD works and if it adds any benefit when driving in the rain on a high-traction surface such as a highway or pavement. Let’s look at it in more detail now.
Does 4 wheel drive help in the rain? Yes, 4 wheel drive offers improved traction and handling in slippery driving conditions such as mud, ice, snow, and rainy weather. Since all 4 wheels are moving the 4wd forward, the vehicle will feel more sure-footed and stable on slippery slick, and greasy surfaces.
But wait! There are limitations as to the level of traction you can expect from your 4 wheel drive when road surfaces are wet from the rain. This article will discuss the pros and cons of driving your non-permanent 4 wheel drive on highways and what damage you could cause in the long term.
Let us now look closer into how a 4 wheel drive assists with traction and stability in the rain.
Does 4 Wheel Drive Help In The Rain
I remember when I drove my first 4 wheel drive in the rain, I was not sure if the road surface was slippery enough to warrant me safely engaging the 4 wheel drive function in the rain. I remember wanting the road to be as slippery and wet as possible because I was so paranoid about drive-train binding. Being a newbie 4 wheeler at the time I didn’t quite understand how the drivetrain binding occurs and which situations could bring on this effect to the drivetrain. So, I just never ever engaged 4 wheel drive when it was raining.
Fast forward to today and, as a matter of fact, I still don’t engage 4 wheel drive in the rain since I’m driving a non-permanent 4 wheel drive. When you have a permanent 4 wheel drive you have the advantage of having all 4 wheels being propelled by the drivetrain and transfer case. This is one massive advantage of an AWD and a permanent 4 wheel drive over a non-permanent 4 wheel drive truck. But, more about that later.
So with a 4 wheel drive, you have the ability to engage 4H in the rain, which will greatly assist with safety, however, you need to determine if the added improved traction warrants risking damage to your drivetrain if you are driving a non-permanent 4 wheel drive. The way I see it, is like this, yes you do have the functionality to improve safety through added traction, but won’t it be better to rather adjust your driving style in the rain instead? As mentioned from the outset, many 4 wheel drivers have found themselves in a situation where, because they have a 4 wheel drive, they fail to adjust their driving style in the rain and end up causing or making an accident. You are better off slowing down and increasing your driving speed and following distance than engaging 4 wheel drive in the rain. Why?
Well, lets answer that question next by looking at how a 4 wheel drive drivetrain works in the rain.
How does 4WD drivetrain work in rain
So when you engage 4 wheel drive, the vehicle doesn’t know it’s driving in rain or snow or mud or sand. These are all low traction, slippery driving surfaces but they all need to be driven on differently. A rainy day creates a lot of slick and greasy road conditions. Now with 4 wheel drive engaged on a highway or dry pavement, you expect the traction level to improve, which it does, however, it doesn’t help much with stopping, which is the highest cause of road accident in winter months when roads are slippery and wet with snow, rain, and ice.
4 wheel drive assists you with pull-offs and does assist with keeping the vehicle more stable. Cornering, however, is not improved by much and if you accelerate in a bend or are overconfident on a windy wet road, it makes no difference if you are driving a 2 wheel drive, All Wheel Drive or 4 Wheel drive, since once the traction is lost, it’s lost, and you are at the mercy of the laws of physics. The difference is that a 4 wheel drive might be able to hold on to traction a tad better or longer than a 2WD but it doesn’t mean that slowing down or applying the safe driving practice in the rain isn’t necessary. In fact, the only time when a 4 wheel drive will prove beneficial in the rain is when you apply the same rules of safe driving to a 4 wheel drive the way you would to a 2 wheel drive vehicle. Only then, you can confidently say, yes a 4 wheel drive is safer on wet roads than a 2WD. It does not give you a license to be overconfident.
Let’s see how rain affects traction
How does Rain affect traction
One of the biggest threats to drivers on a wet slick road is hydroplaning. Hydroplaning, limited visibility, decreased traction and speed are all reasons why accidents happen in the rain. And when you combine them then it’s the perfect recipe for a crash.
On a rainy winter’s day when it’s “raining cats and dogs”, as the saying goes, the traction of your vehicle is limited. It’s not as bad as snow or ice roads which become slick. There are a few factors that cause limited traction on rainy days and they are:
- Tire Pressure
- Rubber Compound of the Tires
- Road Surface Traction
- Speed
Any one of these can aggravate driving conditions and cause a driver to lose control of a car.
Tire Pressure
When the tire pressure, for example, is pumped up too high on a wet road, you are decreasing the ability of the tire to make maximum traction with the road, resulting in only the middle section of the tire to provide traction. An overinflated tire will behave like a narrow tire with limited traction. The surface area of the tires, which Is meant to provide traction is decreased, thus limiting surface area between the tire and the road. This can also cause your tire to behave differently by feeling rather bumpy and not absorbing any differences in an uneven road, but rather bumping over them. When a tire is not making solid contact with a road, traction is lost easier, combine this with a wet road and you have yourself a disaster in the making.
The rubber compound of Tires
This is another reason how traction can easily be lost on a wet road, and that is if you are driving with a very hard compound tire. Hard compound tires are not designed for comfort or superior traction, but rather for longevity and high mileage. They do offer adequate levels of grip for general driving conditions however when the rubber compound is hard, it does not bend, grip, or flex as well as a soft or medium compound tire.
A hard compound tire degradation is slower but also takes longer before it reaches its optimal level of grip. The friction between the road surface and the rubber causes the tire temperature to increase and reach its peak grip phases. So you can understand why a harder compound tire will not fare as well as a softer compound tire since a soft compound tire will heat up faster and be “grippy” enough almost from the get-go. Soft compound tires wear out faster though but offer superior traction on wet and dry surfaces.
Road surface traction
This plays a major role in the extent of traction your 4 wheel drive has in both wet and dry conditions. A smooth surface will create a really slippery low traction condition for any vehicle, 2WD, AWD, or 4WD. Highways are usually made of a coarser tarmac to provide maximum grip under most conditions.
Speed
Speeding on a rainy day is just asking for trouble. It’s the number one killer in the winter season yet people fail to adhere to all the warnings. When the weather deteriorates and road surfaces are wet, decrease your speed immediately. It’s irrelevant what the maximum legal speed is at that time since that could even be too fast for safe driving under challenging driving conditions. Increase your following distance and switch on your headlights when visibility is limited. Obey the guidelines from the traffic notices and listen out for any announcements about hazardous situations to avoid. Never speed in the rain.
Does 4 wheel drive prevent Hydroplaning
When it rains, the water on the road surface makes the road slicker and more slippery. The tarmac used in highways is designed to provide adequate levels of traction under most driving conditions i.e. wet weather, dry weather, snow. Also, most highways are designed at a slight angle to allow drain-off and prevent water build-up and dams of water collecting on roadways. Engineers are constantly coming up with improved methods to improve water drainage from highways.
However, hydroplaning is still a realistic hazard, so let’s look at how we can avoid it and what to do when it happens to us.
How does Hydroplaning Work?
Hydroplaning happens when a layer of water separates the vehicle’s tires from the road surface. If the tire cannot dissipate or eject the water fast enough, and this can be due to tread pattern, tire wear or speed at which the vehicle is traveling, the tire rubber fails to make contact with the road surface long enough, resulting in the driver losing control of the vehicle.
When this occurs the driver interaction is ineffectual since, at that moment when hydroplaning occurs, the vehicle will be gliding or sliding across the road surface as if it were on sleek ice. No amount of braking or turning will affect the vehicle’s behavior until traction is regained. Driving a 4 wheel drive will be irrelevant at this stage.
Now before hydroplaning can happen, the conditions need to be ideal. The 4WD needs to be traveling at 50 mph or (22.35 meters per second) and the water depth must at least be one-tenth of an inch (0.3 centimeters) to create the perfect hydroplaning environment. If the water is collected on a bend it’s even easier for this phenomenon to occur.
Does 4 wheel drive help with hydroplaning
So when you are affected by hydroplaning your vehicle will simply continue moving in the direction it was going at the time of the hydroplaning happening. This is because the inertia will simply cause the vehicle to skid in that direction until traction is regained or until the vehicle stops. This effect happens within seconds and usually lasts for a few seconds. A few seconds could, however, prove long enough to cause you to lose complete control of the vehicle if you don’t react correctly. You could be sent careering off the road into a barrier or worse.
Driving in 4 Wheel Drive on the Highway
So we’ve established that only AWD and full-time 4-Wheel can safely drive on the highway in 4H and not a temporary 4 wheel drive since it’s not designed to drive on dry pavements or highways for extended periods because of drivetrain binding that will eventually occur. We understand that concept. So what happens when this phenomenon occurs to your 4WD?
If you want to read more about driving in 4 wheel drive on dry pavement – click here
When you drive in 4H on a highway you risk all sorts of expensive damage to your drivetrain. Damage can range from failing u-joints, yoke failure, twisting drive-shafts, and torque build-up inside your transfer case and transmission resulting in massive internal damage.
We know that a 4 wheel drive, once 4H is engaged, irrespective of a full-time or part-time 4 drivetrain setup will improve traction, however, in order for that to work, we need to make sure the surface is slippery enough first. Driving on a high-traction surface with a drivetrain that needs a low traction environment to function is a complete no-no. It’s simply because the drivetrain, once locked makes no allowance for differences in speed between the front and rear wheels, when turning, causes all sorts of problems ranging from:
- Wheel hop
- Jerking
- Tight steering
- Jammed transmission, and more
It’s for this very reason that 4 wheel drives in 4H and highways do not gel!
When should you use 4 wheel drive
4 wheel drive should only be used when road conditions are bad and traction is low. This can be any surface ranging from:
- Sleek roadways caused by ice build-up
- Snow packed roads
- Muddy tracks
- Sand roads
- Dirt roads
Any of the above-mentioned environments are perfectly safe to engage 4 wheel drive. You as the driver need to learn to read the road surface when you own a 4 wheel drive.
How to Shift into 4 Wheel Drive
Every 4 wheel drive is designed slightly differently even though the traditional principles still apply. With that being said, there is no single method to engage 4 wheels anymore since manufacturers are constantly improving technology and engineering in these vehicles at an alarming rate. So it is always best to consult your owner’s manual and familiarise yourself with the correct procedure to engage 4 –wheel drive on your specific make and model.
The basic method of engaging 4 wheel drive is as follows:
- When driving in 2H, slow down to below 60mph
- Place the vehicle in neutral and allow the vehicle to coast
- Lift your foot off the gas for a second to allow the transfer case to engage both driveshafts
- Select 4H either by shifting a short transfer case lever or turning a dial
- Engage the gear you were in and continue driving.
Yes, I am well aware that you are not required to select neutral and lift off the gas first, but this is the safest way to engage 4H from 2H if you intend on keeping the 4 wheel drive for a long time.
Conclusion
Owning a 4 wheel drive is awesome and you have so many advantages over a 2WD. Safety is improved with a 4 wheel drive on low traction surfaces and you have the added capability to explore unchartered terrain with confidence. Driving on the roadway with 4H engaged is done at its own risk since the driver needs to determine if the surface is slippery enough to truly warrant 4WD mode on a high traction surface such as a tarmac road or a dry pavement. I would rather err on the side of caution and adjust your driving style and slow down instead, to a safer, more comfortable speed. Leave the 4WD for when you are off-road.