Introduction to 4WD Vehicles: Perfectly Explained
Have you ever wondered, what is 4 x 4 and what does 4×4 mean on a vehicle?
A well-known social media content creator posed a very thought-provoking question when he plainly asked, “What is 4×4 to you?”
This question, of-course, got me thinking since in my 20+ years of experience with 4WD vehicles I just took it on face value.
However, after some careful consideration, I’ve decided to write this post to expose some opinions and explain my version of, what does 4×4 mean in cars.
I started my quest by doing some research on ‘4×4 meaning’ to source a few common explanations or opinions of what 4×4 means to some people.
Let’s see how the masses define if a 4×4 is the same as a 4WD and, what does 4×4 stand for.
- One popular explanation is that 4×4 refers to the terminology used to differentiate between one type of drivetrain system compared to another type such as 4×4 vs AWD. Hmmm, interesting…
- Another opinion is that 4×4 means the vehicle in question most definitely has a transfer case that allows it to switch between 4×4 and 4×2
- Others believe that a true 4×4 means the vehicle with 4×4 badges has locking hubs which is essential when going off-road.
- Many people view a 4×4 as a tool to get them to their desired destination which allows them to engage in other activities such as landscape photography, wild camping, game viewing, hiking, or bush cooking, to name a few.
- Many also believe the 4×4 truck is simply a necessary piece of kit to get you to your desired destination so you can achieve those specific goals.
Whichever way you decipher what 4×4 means to YOU as an individual, let’s look at what four-wheel drive means in technical terms on a 4WD vehicle.
What is four-wheel drive?
4×4 on a truck means it has 4-wheel drive functionality.
The first number means it has 4 wheels and the second number means those 4 wheels are powered or driven.
It could be permanently powered or a par-time 4×4.
Does 4×4 mean the vehicle is always in 4WD? No, not necessarily since many 4x4s are non-permanent or part-time 4WD vehicles.
What does this mean?
To grasp this concept you first need to understand the underlying differences between the two drivetrains.
I highly recommend enrolling on a decent 4×4 Driver training course that will teach you alot in a short time and prevent unnecessary drivetrain damage.
Permanent 4WD Vehicles
Simply put, a permanent 4×4 means the engine permanently sends power and torque to the front and rear axles via the transfer case.
The power/torque is split between the front and rear axles as required thus offering improved traction and control on a variety of high and low-traction surfaces.
A permanent 4WD vehicles have no 2H function to send 100% of its power/torque to the rear axle only.
A permanent 4×4 is always in 4H.
When driving on more challenging surfaces with a permanent 4×4, the driver can select 4H-L to lock the transfer case thus joining the front and rear driveshafts to rotate as a single unit.
When 4H-L is selected 50% of the power/torque is sent to the front axle and 50% to the rear axle.
When driving straight in permanent 4WD vehicles, 50% of power is split 25/25% on the axle to each wheel, however, when turning or when in a cross-axle offroad situation the full 50% of the power/torque on the axle goes to the wheel with the least resistance.
To maintain 25% of power on each wheel irrespective of traction, manufacturers incorporate certain traction assist mechanisms such as diff-lockers, Limited Slip Differentials, and traction control.
These traction aids are incorporated to maintain traction by sending 25% of the engine power/torque to each wheel on the axle, thus allowing the wheels with traction to propel the vehicle forward.
Part-Time 4WD Vehicles
Part-time 4WD vehicles means the vehicle is predominantly driven in 2H when driving on high-traction surfaces such as dry pavement or the highway in the city.
A part-time 4×4 relies on driver input to select 4H once he determines the driving surface is slippery enough with minimum surface traction.
Part-time 4WD vehicles should not be driven in 4H on a high-traction surface such as dry pavements or highway driving since it eventually causes drivetrain binding, wheel hop, and premature tire wear.
When 4H is selected on a part-time 4×4 the transfer case locks the front and rear driveshafts to rotate as a single unit.
Engine power/torque is split 50/50 between the front and rear axles.
It now functions exactly the same as a permanent 4×4 with the transfer case locked 4H-L.
Good read: Exploring the Power of 4WD
NB: A low level of slippage on the wheels is necessary for the 4×4 system to work effectively without risking drivetrain or tire damage.
How Does 4×4 Help
4×4 helps because it allows you to drive on slippery low-traction surfaces with a decent measure of confidence and control.
It also allows you to drive on uneven, challenging terrain where a normal vehicle with only 2H cannot.
4×4 helps you to drive safely on low-traction surfaces such as:
- Snowy roads
- Gravel/Dirt roads
- Icey highways
- Sand dunes
- Rocky roads
- Wet roads
- Muddy tracks
- Grass
Now that we understand what 4×4 is, how it helps, and the differences between permanent 4WD vehicles and part-time 4x4s, let’s now look at some interesting features of the 4WD system.
What are the features of 4WD?
The best 4×4 vehicles have many weapons in their arsenal to assist when driving on rough and challenging off road terrain.
These features include but not limited to the following:
Improved Traction:
As mentioned earlier, when you are driving on a low-traction surface with a 4×4 it propels all 4 wheels thus making it safer and more stable to drive.
Traction and stability are improved immediately when 4H is selected.
When 4WD is engaged, the front wheels pull forward while the rear wheels push forward simultaneously resulting in superior off-road capability.
High and Low range Gears
The 4H and 4Lo gears allows you to drive on a variety of uneven, slippery surfaces without damaging the vehicle if done correctly.
4H means you are still using high-range gears, similar to when you are in 2H, except all 4 wheels are being propelled instead of only 2.
The 4H gears are ideal for driving in dunes, muddy tracks, slippery roads, etc. where there isn’t too much risk of damaging your vehicle and where you can safely drive up to speeds of 55-60mph.
Low range gears are a separate set of gears designed for extreme off-road scenarios.
4Lo gears are ideal for challenging technical tracks where road surfaces are uneven and slippery, or combinations of the two.
Low range is designed for slow driving where line choice is important to successfully overcome the obstacle.
Locking Differentials
Locking differentials, lockers or diff-lock all refer to a differential that can be locked via air or electronically in 4WD vehicles to allow both wheels on an axle to rotate as a single unit.
Locking diffs are used when you are driving on uneven, challenging offroad conditions where 2 wheels could possibly become airborne i.e. in a cross-axle situation or when traction is extremely low.
Diff Lockers should only be used to overcome an obstacle and be turned off once it is safe to do so. NEVER drive or turn on high-traction surfaces with the diff lockers engaged.
Various Offroad settings
Most modern 4WD vehicles offer a variety of off road settings to make off-roading easier.
Driving modes adjust certain settings on the vehicle such as brakes, throttle responsiveness, steering sensitivity, transmission shifting patterns, and even suspension ride height on certain makes equipped with pneumatic suspensions.
Many modern 4x4s are equipped with terrain-specific modes such as sand mode, icey/snow conditions, rock crawling, and towing.
With a quick turn of a dial, these driving modes are designed to adapt the vehicle to perform optimally on the required surface.
Traditional 4x4s have the basic 4H (High-range) 4Lo (Low range) and recently, 4A (4WD-Auto)
Electronic Traction Aids
Many modern 4WD vehicles are equipped with electronic traction aids that works in tandem with the diff lockers and 4WD gearing.
These aids include downhill assist, Hill-hold assist, Traction control, anti-stall assist, and many more.
They are all designed to make off-roading safer and easier on the vehicle’s mechanical drivetrain system.
Other Supporting Features Include but not limited to the following:
Good Ground Clearance
Ground clearance refers to the ride height of the vehicle.
It is one of the most basic but very important dimensions of 4WD vehicles used for off-roading or Overlanding.
Ground clearance is measured as the maximum distance between the lowest part of the vehicle and the road surface.
- The ideal ground clearance for off-roading should range from 8.8 inches to 10.8 inches or higher, depending on the obstacles you want to tackle.
- For gravel, mud and dunes you’ll need 6.6–8.7 inches of ground clearance.
- 9.4 inches is sufficient for Overlanding.
- 10.8 inches for rock crawling.
- 8–10 inches is recommended for heavy snow.
Robust Chassis
Most 4WD vehicles have a Ladder frame chassis, also known as a body-on-frame chassis.
The Ladder frame chassis is a robust metal framework consisting of two large metal beams joined together by shorter support beams in between.
With a Ladder frame chassis, the body and engine of the vehicle are mounted on top of the ladder frame making it a robust structure that is ideal for Commercial Trucks, SUVs, and 4×4 Utes.
It is optimally designed for vehicles intended to carry heavy loads for extended periods.
Many modern 4x4s come equipped with a Monocoque design.
This means the chassis is forged into the basic structure of the vehicle creating one singular object known as a Uni-body, or Monocoque.
Monocoque chassis is mainly used in the production of luxury SUVs, luxury sedans, and hatchbacks, offering superior safety, ride dynamics, and fuel economy due to its lighter framework.
Excellent Approach and Departure Angles
The approach angle of 4WD vehicles signifies the maximum angle between the lowest part of the front bumper and an obstacle.
A vehicle with a low approach angle risks scraping or damaging the front bumper and undercarriage when tackling obstacles.
The approach angle of 4WD vehicles dictates what the steepest slope or obstacle a vehicle can climb without bumping or scraping its front bumper.
The departure angle is measured from the vehicle’s rear lowest point as it exits an obstacle.
A low departure angle can lead to snagging or damage to the rear, possibly causing the rear plastic bumper to tear off.
It signifies the steepest descent a vehicle can manage without scraping or hitting its rear bumper against rocks or slopes.
Enhancements like aftermarket metal bumpers, lift kit, and larger tires can significantly improve the departure angle.
What is the mechanism of 4WD?
The 4×4 mechanism of 4WD vehicles consists of the front axle and front diff, the front drive shaft, the transfer case connected to the transmission, the rear drive shaft, rear axle, and rear differential.
This makes up the 4WD vehicles drivetrain system.
The 4WD system gets torque/power from the engine that gets transferred to all 4 wheels simultaneously.
The 4WD systems transfer case splits torque output 50/50 to the front and rear differentials.
This is the basic mechanism of a 4WD.
Helpful Resources
Final Thoughts
In summary, 4WD vehicles or 4x4s can mean different things to different people, however, the technical definition of the 4×4 drivetrain is that it has 4-wheel drive functionality.
The first number in 4×4 means it has 4 wheels and the second number means those 4 wheels are powered or driven.
It could be permanently powered or a par-time 4×4.