The 4X4, or put, 4-wheel drive, is a type of drivetrain mode where all the four wheels of a vehicle are spinning. The 4H is also famed for being the best drive mode you can switch your car to if you are dealing with the “testing” terrains that are hard to thread. But can you use 4H on the Highway? “What effects does it have on your car?” – if you have been wondering, go along this article.
Generally, you can use 4H on the Highway. However, this is not advised, as “binding” can occur (central differential/transfer case is locked), a driveline issue that comes up when the front wheels try to rotate faster than the rear wheels. Frequent occurrences of this can wreck your transmission.
Generally, four-wheel-drive vehicles were designed to improve traction and stability in off-road environments. However, the design of these vehicles also affects how the wheels rotate.
All 4 wheels synchronize together to provide stability and traction in all directions. This synchronization is key to the effectiveness of 4WD vehicles. But locked central differential will ALWAYS put your transmission in a bad situation that can cause havoc to your car.
What 4H Is and How It Works:
In our vehicles, some components are responsible for the sole thing our car does: driving. As a result, these parts run through various mechanical processes (among themselves and within them and other car parts) in different driving situations, manually or automatically.
In 4WD cars, these parts are front driveshaft, rear driveshaft, and front and rear differentials. The engine is connected to the transmission system with altered speed and torque and sends power to the front and rear driveshafts. These shafts are connected to the rear and front axles.
These driveshafts above, in essence, receive torque from the transmission and send them to the respective axles they are connected to, and thus, the car moves.
I have created the infographic below that covers whether you can use 4H on the highway. (You are welcome to use and share but please credit back if you do so.)
4H, also known as High Range 4-Wheel-Drive, is a 4WD model available in vehicles with either part-time or full-time 4WD vehicles.
When on this mode (in part-time 4WD vehicles), the transfer case locks the rear and front driveshafts together, and this results in the sharing of torque provided into 50% each for both driveshafts, and subsequently, 25% torque for each wheel.
Reasons You Should NOT Use 4H on the Highway:
1. Transmission Windup:
When we drive around corners on the Highway, it is no news that the outside wheels have to run more distance than the inner wheels. However, as seen in recent cars, transfer cases and differentials have been used to minimize the slip effects that occur when we run through corners, ensuring required torque is supplied to the wheels as needed.
But in the course of this, we have seen cases where driveline issue; a situation that messes up your transmission, and it is caused when the front axle turns faster than the rear axle when cutting through a corner on the Highway frequently occurs well.
This not only messes up your transmission but also affects your handling negatively. This issue is called transmission windup.
A significant problem resulting from this issue is that “play” is disrupted in the car parts that propel the vehicle. This reduces the net efficiency and smooth running of your car.
What Play Is:
In the arrangements of car parts, no gears, shafts, and joints are bolted with other features perfectly tight. Instead, there is always a space that allows for proper “rubbing” of these parts against themselves or on their own. This slack is called “play.”
2. Increased Wear and Tear:
As it is generally hammered, running on 4H is the ideal drivetrain you should switch to when you need extra traction to travel on the terrain you are threading, but on dry pavement (highways)? – No is the definitive answer.
When on 4H, and you are driving around a corner, the front axle will have to run faster than the rear axle to ensure the safest driving condition.
But when the central differential is locked and a corner is driven through, the rear axle that has to run slower than the front axle is now forced to be on the same running page, as all the central differential ensures is that the front and rear axles rotate at the same speed.
Physical “drag” by the rear wheels can be noticed when this happens. This, in the long run, will make the tires’ upkeep more expensive. This issue is related to transmission windup likewise.
How To Know If Your Car is Binding:
The most common things that ascertain that your car is binding are as follows:
- Tire squeals
- Continued vibration
Advantages of Driving on 4H on the Highway:
The 4H mode is a drivetrain mode that is efficient and capable of improving your driving. Below are among the perks you get in your driving when you drive on 4H:
1. Increased Speed:
The 4H drivetrain, as known, is a 4WD drive mode where all 4 wheels are provided the torque to propel the vehicle. When all wheels rotate and move the car simultaneously, this will generally improve driving speed.
2. Improved Traction:
Compared to the traditional 2-wheel drive, where the rear wheels are the ones doing the driving, and the front wheels do the steering, in 4H, all wheels have their claws gripped into the ground and “work,” and this results in improved traction in the overall sense.
This ensures the major goodness of the 4H is; ensuring driving safety. The 4H mode ensures maximum driving safety when returning home from work.
It’s raining, or maybe you’re just going for a job interview during the snowy era and need to arrive fast, or perhaps you want to get to the store during the festive period to get presents for your little daughter and need to struggle with the snow on the road.
The 4H is your best bet when choosing a drive mode when facing these situations.
Regulations for Driving in the United States:
In antagonization to the UK driving, in the US, you can make u-turns as you deem.
Generally, 55mph is the specific speed limit you should travel in on 4H, but you can exceed this limit while noting that it is at the expense of your transmission.
In the USA, speed limits from state to state differ; therefore, it is advised you research the state you're driving to if you don't want the police tailing you.
The speed limit in all US states for all highways ranges from an urban low of 25mph (40km/h) to 85mph (137km/h) at a rural high.
To drive whatsoever in the US, you must possess a US tagged driver's license or an international driver's license.
To be able to drive on any highway in USA, you have to have an up-to-date insurance policy that protect you against accidents.
The use of a seatbelt, abiding by road signals. Lane configurations; for dashed lines on the road, cars can change lanes and remain in their respective streets if driving on roads marked with a continuous white line.
Yellow lines indicate you must maintain your route without switching.
Truths and Myths About Transmission Windup:
-Going up straight always reduces windup
This is not true when you are driving on dry pavement.
-Going up straight can only reduce windup if you are driving on a loose-grained terrain
-Turning left and right reduce windup
-This only increases the windup and will better the chances of getting your transmission exploded
-Reversing straight back reduces windup
-Reversing straight back doesn’t cancel out the accumulated windup in your wheels.
Common Problems With Using 4H on the Highway and Effects:
HOW TO RESOLVE
Driving with a locked central differential (on all-time 4X4 mode, and locked hubs in part-time 4X4) on dry pavement while cutting corners
The transmission system gets messed up and handling is deterred
Leaving the central differential open.
Increased wear and tear
Driving with a locked central differential (on all-time 4X4 mode, and locked hubs in part-time 4X4) on dry pavement while cutting corners
Tire upkeep costs more in the long run
Leave the central differential open when you’re not off-roading
NB: WINDUPS ONLY OCCUR IN VEHICLES WITH PART-TIME 4X4 OR TRANSMISSIONS WITH MANUALLY LOCKABLE CENTRAL DIFFERENTIALS
How To Fix/ Reduce Windup:
- Switch off 4WD or unlock the central differential.
- Drive back in circles if you feel the hardness in steering your vehicle after finishing a turn.
- Use 4WD only on a loose-grained road.
- DO NOT jack any of the wheels of the vehicle up. This results in releasing all the accumulated tension in the wheels all at once, which is not ideal because the wheels receive binding tension varyingly.
Can You Turn 4-Wheel Drive on While Driving?
When you are driving on the highway, and you notice the need to switch from your current drive mode to the 4H, perhaps due to that the road is slippery or maybe you want to run through the mud, you might sometimes feel like you won’t you be messing your car if you switch it on the fly.
As far as this is concerned, there is no issue whatsoever with shifting to the 4H if you are on the fly.
The 4X4 drive mode that this can't be done for is the 4L drivetrain. When switching to this mode, the vehicle has to be in neutral, and even after the 4L has been engaged, the system will take a bit while to set itself up for movement. This is because the other drivetrains use high gears in the propelling, while the 4L uses the low gear.
How the 4X4 Works:
In our everyday driving, we all tend to find ourselves in different situations that get us wondering about the actual type of vehicle we should be using. For example, in some locations, the road is always covered in snow for around 7 months, while in some places, the four seasons occur at their speculated time, as they should normally.
This also proves right the need for certain types of cars for people that have to thread swampy areas almost EVERY SINGLE DAY. These needs are to what engineers develop engines that can cater to our day-to-day drive needs.
In vehicles, these cardinal parts can’t be done without working them, with the most important being the drivetrain and powertrain.
The drivetrain consists of vehicle parts that work together with the primary aim of propelling your vehicle forward. In contrast, the powertrain consists of the engine combined with the drivetrain and other few parts.
4X4 Drivetrain Mode- The Details:
The 4WD system consists of 3 essential components: the transfer case, locking hubs, and differentials.
The transfer case encompasses a device that allows for the sharing of the torque between the front and rear wheels. Then transfer case locks the front axle to the rear axle driveshaft, making the wheel spin at the same speed.
Differentials (Front and Rear):
Torque is sent from the driveshaft to the front and rear wheels. They help to make the right and left wheels rotate at different speeds. The differentials allow speed difference between the inner and outer wheels when you go around corners.
The locking hubs disconnect the front wheels from the front differential. This helps reduce wear and tear on the front wheels and improve fuel economy in the long run.
The 4X4 is a drivetrain system that provides power to all four wheels to propel the vehicle forward. However, it is imperative to note that when your car is on 4WD, it is on 2-wheel drive primarily and will remain in this drive mode unless the current situation demands otherwise.
This vehicle stays on the 2-wheel drivetrain to improve fuel economy and reduce tear and wear to the vehicle parts.
When the vehicle runs and tries to cut a corner, the outer wheels are forced to run more distance than the inner ones. Therefore, with the standard drive mode, the vehicle will slip when it takes this turn.
This is more evident on rainy or snowy roads. People who have experienced this bizarre occurrence will tell you it’s better than having dinner with Lucifer and will always ask you to try to avoid this by all means possible.
Generally, all needed to know about the 4WD systems is that they can provide power and stability to vehicles that require enhanced movability.
They are also popular among off-road enthusiasts and provide a more soothing driving experience when used in sand or snow. In addition, the system utilizes several technologies to offer enhanced performance and reliability.
These engines typically include a turbocharger and a gearbox to increase power and torque. Additionally, this drivetrain utilizes differentials to provide stability when cornering or driving on rugged terrain.
How Does a 4WD Transfer Case Work?
The transfer case is a device consisting of a set of different gears used in four-wheel-drive vehicles to transfer power to the front and rear axles. A transfer case is essential in a four-wheel-drive as two different shafts are mounted in the engine. The transfer case also is used for obtaining low and high torque transmission.
The gearbox’s output shaft acts as the transfer case’s input shaft. We have the lay shaft and the output shafts in the setup too.
This input shaft consists of a helical gear that constantly meshes with the gear in the layshaft. Similarly, another gear in the layshaft meshes with the gear in the output shaft. A dark clutch also slides over the output shaft, which is located between the input and output shafts.
The output shaft is connected to the rear differential and has a fixed gear that rotates with the shaft and a sleeve mounted on the bushing. The output shaft sleeve is connected to another shaft, the auxiliary output shaft, with a belt or a chain. This auxiliary shaft is connected to the front differential.
The sleeve can be connected to the fixed-gear using a clutch dog that slides over it. The shifting can be done manually or electrically to engage the dog’s clutches.
How the Transfer Case Runs:
When the dog clutches are engaged, the input shaft rotates, which in turn rotates the output shaft. In this case, motion is transmitted from the input gear to the output gear through the lay shaft gears. This generally reduces the speed and makes the vehicle behave like a 2-wheel drive, as all power is transmitted to the rear axles, and high torque is transmitted.
But when the dog clutch engages with the input gear, the input and output shafts rotate simultaneously, resulting in low torque transmission. Here, the vehicle is still in a 2-wheel-drive.
Subsequently, when the dog clutch engages with the fixed gear mounted on the output shaft, the sleeve rotates, making the belt drive the auxiliary shaft. This arrangement makes all 4 wheels turn, but at low torque.
To make the engine run on high torque transmission, then 2 dog clutches must be engaged with their respective gears.
However, it is imperative to note that the transfer case transmits equal torque to the front and rear axles at the same speed and can be completely locked.
The Other Types of Drive Modes:
It is no surprise that vehicles come in various base systems. We have 4 types of drivetrains in cars. We have then FWD (front-wheel drive), RWD (rear-wheel drive), 4WD (four-wheel drive), and AWD (all-wheel drive).
Front-Wheel Drive (FWD):
In front-wheel drive (FWD), the car with which it’s coupled always has the power provided by the engine supplied to the front wheels.
The major setback with this drivetrain is that the front wheels are always burdened with the work of propelling the engine while constantly having to be responsible for the steering of the vehicle.
Also, it isn’t as swift as it should be when cutting corners. Although, the FWD system makes vehicles more stable and drives well on mildly snowy and slippery roads.
Rear-Wheel Drive (RWD):
RWD is a drivetrain system where the power provided by the engine is supplied to the rear wheels. This is accomplished by passing torque from the transmission through the propeller shaft through a differential that distributes power between the 2 wheels, which propel the vehicle.
In the RWD, the front wheels DO NOT receive any power from the engine, as they are only responsible for the car’s steering. In contrast, the rear wheels are the only wheels saddled accountable for propelling the vehicle.
All-Wheel Drive (AWD):
The AWD is a drivetrain system with the cardinal parts of the transfer case, front, center, and rear differentials, with the central differential being the “nucleus” of the setup. The central differential is a device that consists of several gears that divide power between the front and rear axles.
Also, the AWD systems have sensors to detect if a wheel or wheel is/is losing traction or are not performing as expected and make the engine provide torque as deemed due.
However, the AWD is not the ideal drivetrain to take to an off-road quest, although it is more suitable for highway driving as it provides more traction and speed. This is how the electronic system in the modern vehicle works.
For the “old ladies,” a driveshaft goes into the rear differentials that distribute power to the rear wheels. There is also a transfer case and driveshaft at the front that sends power to the CV joints that, in essence, propels the car.
However, the major drawback with this drivetrain is that tires wear out faster as they are always working, which in turn makes you need to change all four when one wears out. This insinuates more expensive tire upkeep.
Similarities and Differences Between the Four Drivetrains:
Number of spinning wheels
4 wheels are always spinning
The 2 rear wheels spin primarily, but change to 4 as situations demand
Driveshaft and rear differential
Driveshaft and rear differential
Transfer case and central differential
Transfer case, locking hubs, and differentials
Front most times
Front, center, or rear
Either front or rear (front mostly)
Mode of transmission
Electric and manual
Frequently Asked Questions (FAQs):
Is 4X4 and AWD the same?
No, they are not. In 4X4, the two rear wheels run, and the front wheels are engaged when due. But in AWD, all wheels are constantly spinning, giving you the ‘’goosebumps’’ whenever you take a sharp cut. Also, you can turn off and on the 4X4 as you deem fit.
Can AWD drive on sand?
Yes, it can. The central differential must be locked, and the low gear range should be engaged.
Is AWD or 4WD better in the snow?
The AWD is the better option, as it continuously senses the wheel torque should be transferred when you are driving, unlike the latter, where the wheels are locked and rotated at the same speed without serving any preferential to the wheel needs torque.
This is Surya. I am an experienced off-roader. I have been off-roading for many years across several terrains. I am passionate about 4×4 driving and want to share my knowledge and experience with others.
My goal is to provide you with the most comprehensive and unbiased information about off-roading.
I curated this article through my personal experience and expertise, and I hope it helps you with what you are looking for.