4-Wheel-Drive 101 - Here's All You Need to Know About 4x4 Systems

Don't know what 4x4 is? Confused about what differentials are? This article clears up everything.

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30. Apr 2023
4-Wheel-Drive 101 - Here's All You Need to Know About 4x4 Systems

Off-roading is fun but there’s no doubt that it is challenging. You need traction to make it on the trail so that you don’t get stuck (especially in a remote area). It is also needed to prevent your vehicle from slippage. The 4-wheel drive (4WD) system is key to achieving traction. 

There are several 4WD systems available in a variety of configurations, each with its own advantages and disadvantages. These are part-time and full-time off-roading (aka automatic off-roading), and all-wheel drive. There are a couple of others as well. 

The following tells you all you need to know about 4WD systems: 

History of the 4-Wheel Drive System for Off-roading 

We saw the first 4x4 car for off-roading emerge in 1903 out of the Netherlands – made by the Spyker car company. Years later, the Four-Wheel-Drive Company’s Model B was used by the U.S. Army during World War I. It could be driven in muddy, snowy, and mountainous terrain.

In the 1960s, the first recreational 4WD vehicles were introduced, including the Jeep Wagoneer and the International Harvester Scout. The next two decades saw an increase in sophistication. Many vehicles were equipped with locking differentials. 

These allowed the driver to lock the wheels on each axle together, for more traction in difficult terrain. Electronic traction control was also introduced to prevent the slippage of tires and improve overall vehicle stability. 

As a result, overlanding got a lot easier thanks to these newer SUVs. Today, 4WD technology has become an essential feature for many off-road enthusiasts and is commonly used in vehicles that need to operate in extreme weather conditions, such as snow and ice.

overland 4x4 4wd all terrain


Major Types of 4WD Systems

Part-Time 4WD Systems

We start with the most common four-wheel drive system in the market. Part-time 4WD systems provide power to all four wheels – when you need it. This means that it only utilizes the vehicle’s full capability when necessary – when the terrain or weather conditions get challenging. 

When you engage 4WD, the transfer case sends power from the transmission to the front and rear axles. It is a two-speed transfer case, which allows you to switch between two gear ratios and select a low-gear range. 

On engagement, the system provides the front and rear wheels with equal power (Lo). When it is not turned on, the SUV operates as a standard two- or rear-wheel drive vehicle (Hi). 



Part-time 4WD is great for traction. This is because of the low-range system that gets you more torque at slower speeds, providing you with more traction and control in difficult situations. Equal power is supplied to both axles, protecting you on slippery or uneven terrain. 

At the same time, because it can shut off when you need it to, it is more efficient than a full-time 4WD system. The power is only sent to two wheels then and this is why the vehicle consumes less fuel. It also means that the drivetrain gets less wear and tear. 

Another reason for its popularity is its simplicity. Part-time 4x4 vehicles are less complex than their full-time counterparts, meaning that they are easier and more affordable when it comes to maintenance. More drivers tend to understand how it works. 



This system is ideal for off-roading as you get maximum traction. But on dry, paved roads, there’s wear and tear on the drivetrain and reduced fuel efficiency. There’s also the chance of increased wear and tear due to frequent usage or usage in extreme off-road conditions. 

Also, it can be more difficult to control on pavement than a two- or full-time four-wheel drive vehicle. This is because the 4x4 setup can cause the vehicle to feel less stable, particularly when cornering or driving at high speeds. 

The weight of the 4WD system can make the SUV or truck feel less nimble – a disadvantage when driving in crowded urban areas. 

Also, it can be challenging to turn the system on/off. Some vehicles must be completely stopped and shifted into neutral. This can be inconvenient and time-consuming, particularly in situations where the driver needs to quickly switch between two-wheel and four-wheel drive.


Full-Time 4WD Systems

Full-time 4WD has become more common these days as SUVs and trucks have become a lot more efficient. These 4x4 systems provide a consistent flow of power to all four wheels, all the time. The power is sent to both axles via a transfer case or a center differential.

These systems provide constant traction, regardless of the driving conditions. Those who live in the countryside or constantly have to face wet roads love them. Full-time 4WD is thriftier on paved roads than part-time 4WD since the driver doesn’t have to engage/disengage constantly.


4-Wheel-Drive System without Transfer Case

4WDs without transfer cases are increasing in popularity in newer vehicles. These are becoming increasingly common in modern vehicles and are also known as single-speed or automatic 4WD. But how do they work exactly?

Well, these bad boys rely on a center differential and electronic controls to send power to all the wheels. But as their name suggests, they don’t use a transfer case. Instead, there are sensors used to detect wheel slippage and adjust the distribution of power accordingly.



4WD systems without a transfer case are simpler and more lightweight than their traditional counterparts. This is no surprise since the additional weight of a transfer case isn’t there. Also, these systems tend to be more fuel efficient as a result. 

For the very same reason, they also bring about better handling. Also, due to fewer mechanical components, they’re also more reliable and less unsusceptible to failure. Furthermore, these systems can be used on all types of terrain – unlike traditional systems which only work off-road. 



While these systems are great, they’re at a disadvantage when you compare them in terms of capability. They don’t have the low-range setting that the systems with transfer cases do. So, you could have trouble in deep mud, sand, or snow. Rock crawling is also a tad bit more difficult. 


All-Wheel Drive (AWD) Systems 

This is one of the most common four-wheel drive system choices today. But while it powers all four wheels, it’s not really meant for rugged off-road driving. There are no Lo or Hi buttons to help you when the going gets tough. The power’s not split evenly between the wheels. 

Many new cars use automatic AWD – a system that can make adjustments on the fly to send power wherever it’s needed. It detects whenever a vehicle is about to slip and it corrects it. If you’re looking for added stability on paved roads, this beats any front-wheel drive car out there.

Like 4x4, AWD powers all four wheels simultaneously. It distributes power to the wheels with the most traction to defeat slippery and uneven conditions. The power sent to each wheel varies – some systems send more power to the front or rear wheels based on the situation.



AWD provides improved traction than your average drivetrain system, which is essential for off-roading. It does allow you to maintain better control over your vehicle and helps prevent it from getting stuck. As a result, it likes to reduce some significant risks when off-roading.



AWD vehicles tend to be less capable than the more traditional 4x4s. As a result, they’re more suited to light off-roading. An example of this is that AWD is better for winter driving on the road, instead of deep snow. 


overland truck extreme terrain 4x4 4wd


Other 4WD Systems

4WD System with Portal Axles

A portal axle is different from your average axle that connects to the wheel hub. Instead, it sits above it and uses a set of gears to send power from the diff to the hub. The axle provides gear reduction which allows the wheel to rotate slower – the torque still remains the same. 



Portal axles may seem unorthodox, but they do provide you with a handful of advantages. For example, they increase your vehicle’s ground clearance, so that it is higher off the ground. Because of this, you can fit your vehicle with larger tires for more traction. 

These axles also improve the approach and departure angles – helpful for steep inclines and slopes. Additionally, these axles improve the vehicle’s stability and increase control on uneven terrain and surfaces. 



There are disadvantages of 4WD with portal axles such as the complexity of the system. This means that you’ll have to maintain them more than your standard axles. This also means that the repairs are relatively more complex. Also, the cost is higher and so is the weight. 


2/4WD System with Engageable Hubs

Here’s a rather old-school but effective way of transforming your two-wheel drive vehicle into a 4x4; it is hence a part-time time 4WD system. You simply stop the vehicle and manually lock the hubs on the front wheels to connect them to the drivetrain. 

When you’re done and don’t need 4WD anymore, simply unlock the hubs. This turns the vehicle back into a two-wheel drive. 



The advantages of the system are similar to the part-time 4WD system mentioned above. These include higher fuel savings, reduced wear and tear, the best of both worlds, etc. 



As you may be thinking, while it is certainly appreciable that the system allows you to switch between 2- and 4-wheel drive, it sounds a bit difficult. Well, that’s one of the biggest criticisms of this system, as you’ll have to manually make the switch by getting out of your vehicle.


Differentials in 4WD

A differential is a component that allows the wheels on the same axle to rotate at different speeds simultaneously. This is needed as when a car turns, the wheels on the inside of the turn travel a shorter distance than those on the outside, so they’ll need to rotate at different speeds. 

The diff helps distribute the engine’s power evenly to both the wheels on the axle – they’ll be rotating at different speeds. There are center, rear, and front diffs – the center distributes torque between the front and rear wheels; the other two to the rear and front wheels respectively. 

The various types of differentials are the following: 



This does the job of a differential without providing any additional traction. It can be problematic on uneven terrain so you can get stuck if a wheel loses traction.


Also known as a viscous coupling differential, it uses a clutch or viscous fluid to provide additional traction when one wheel loses traction. It is good for mild off-roading.  

Automatic Locking 

This uses mechanical or hydraulic pressure to lock the differential and engage both wheels of an axle when one of them loses traction. It’s prone to overheating and wear, but good generally. 

Selectable Locking 

This allows the driver to manually engage or disengage the locker, hence providing full power to both wheels of an axle. It is ideal for extreme off-road situations but is costly.


4WD Lockers

A locker is different from a differential in the sense that it can be installed in one to lock the two wheels on the same axle together, forcing them to rotate at the same speed. This is useful when you need both wheels on an axle to be turning together to maintain traction.

Below are its different types:



These lockers engage automatically when a wheel slips to provide extra traction. They are also known as Detroit lockers and they can be noisy and create handling issues on paved roads.


Mechanical lockers engage both wheels of an axle at the same time, providing equal traction to both of them. They’re activated by the driver and are reliable, but disengaging them can be hard and they’re pricey as well.  


These are similar to their mechanical counterparts but are activated by an air compressor. They’re even pricier but are easier to use.


Electronic or software lockers use sensors to detect wheel slippage and engage the locker automatically. They are quieter and smoother but can be more expensive and less durable in harsh conditions.


expedition all-terrain overland 4x4 truck



4-wheel drive systems are considered essential for off-roading due to the extra traction and stability that they provide. There are several types of these systems, each one suitable for a different type of driver. 

To sum it up, those looking to off-road frequently and in harsh conditions should opt for 4WD with a transfer case. If you want something that’s more versatile, then you can opt for an automatic 4WD system. For light off-roading or just more traction on-tarmac, AWD gets the W.

There are mods such as portal axles if you’re looking for more ground clearance. While searching for off-roading vehicles on the market, you’ll see there are several types of differentials and after-market lockers available as well. 

Before buying a vehicle, just make sure that you give our piece a read to find out the advantages and disadvantages of each system and component. 

To get your own 4x4 overland adventure vehicle, check out Expeditionmeister here: https://expeditionmeister.com/



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