Front? Or maybe the back one? Or, perhaps, completely complete? Which of these drive types is the best and which one to give preference to? Every car enthusiast asks such questions when choosing a new car.

About all types of car drive, without exception, there are both real arguments and myths, both positive and negative, and can lead to a number of opinions in favor of one or another option. But this article will focus exclusively on the all-wheel drive of the car. In particular, about its advantages and disadvantages.

First, it's worth understanding the terminology. Four-wheel drive vehicles usually operate in 2 modes: AWD and 4WD. What is the difference? The first one implies four-wheel drive operating in constant or automatic modes. The second is all-wheel drive, manually connecting and disconnecting.

The purpose of the plug-in all-wheel drive is that the vehicle's transmission can work in two ways. One provides a stable transmission of torque exclusively to one axle - usually the rear. This increases the vehicle's top speed and other characteristics. The other transmits power to both axles simultaneously, increasing traction when needed.

By the way, this very torque is distributed thanks to a differential containing a certain number of gears. Modern all-wheel drive systems have 3 differentials. This allows the power to be distributed evenly to all wheels, ensuring a comfortable ride without any resistance.

The center differential carries the bulk of the load as it distributes torque and simultaneously transfers it to both the front and rear differential.

Exclusively AWD systems do not have such a center differential, which makes driving such a car on a clean, dry road not very comfortable.

Now it's time to talk about the disadvantages of all-wheel drive. Despite the fact that four-wheel drive combines the advantages of other types of drive, it is not so easy to drive a car equipped with it in real conditions.

Especially on difficult road conditions. After all, if a rear-wheel drive car in some situation requires a decrease in gas, and a front-wheel drive, on the contrary, an increase, then an all-wheel drive will require both. Everything will depend on the level of traction, driving speed and other factors.

For this reason, it is extremely difficult to predict in advance what to do at a critical moment. Moreover, a car with four-wheel drive can lose stability in an instant. Moreover, without giving the slightest prerequisites for this.

Another disadvantage of all-wheel drive is the higher fuel consumption. This is explained by the all-wheel drive device itself. In addition, all-wheel drive systems are expensive, both maintenance and repair. Of course, the make and model of the car significantly affects the cost of maintenance. However, any four-wheel drive system has a much larger number of parts and a more complex design.

As for the advantages of all-wheel drive, the most obvious of them is the increased cross-country ability. It is for her sake that such cars are bought.

Along with this, all-wheel drive vehicles have a pronounced dynamics, allowing you to take off without wheel slip, regardless of the condition of the road surface. But, as it was said earlier, only one can fully experience all the advantages of an all-wheel drive.

In conclusion, I would like to note that none of the drive types can be an absolute panacea in a given situation. Driving skills, ability to control and analyze the situation, composure are more important for the driver. It is these factors that are most important. And the drive ... Its role, for the most part, is optional.

May be of interest:

Scanner for self-diagnosis of the car

When choosing a new car, the future car owner is faced with the question of which drive to choose? Front, rear or full? To find the answer to this question, you need to know the advantages and disadvantages of all types of drive, so that the choice is fully conscious.

Characteristic

So let's take a look at four-wheel drive vehicles. There are two types of this drive - AWD and 4WD. AWD type implies the operation of the mechanism in automatic or constant mode, and 4WD mode provides for manual on and off. That is, the transmission of torque is provided only to one axle, usually to the rear, and if necessary, the front axle is connected. On the other hand, the AWD all-wheel drive scheme is constantly in automatic mode, transferring torque evenly to both the front and rear axles.

Control

Driving a car has its own characteristics and difficulties. While manual four-wheel drive vehicles generally behave on the road in the same way as rear-wheel drive vehicles, the same cannot be said for permanent four-wheel drive vehicles.

For example, if, in a situation where a front-wheel drive car requires an increase in engine speed, and a rear-wheel drive, on the contrary, a decrease in speed, an all-wheel drive car will need either one or the other, depending on various factors, such as the quality of tire grip. , speed of movement, trajectory of turn, etc. This complicates driving because you need to be able to predict the behavior of the car and plan your actions in advance. The situation is also aggravated by the fact that an all-wheel drive car can suddenly lose stability, without visible prerequisites.

Cons of 4WD cars

The negative qualities of all-wheel drive systems, in particular systems with manual control, include increased wear of transmission parts, increased noise,. This is due to the design features of the system itself. For example, there is a rigid connection between the axles of a car equipped with a permanently connected four-wheel drive, which consumes additional energy.

The all-wheel drive system has a number of limitations during operation - the system cannot be used when driving on a hard and dry road, which means that the engine traction is not fully used. In addition, four-wheel drive vehicles are more expensive to manufacture and therefore more expensive. They are also more expensive to maintain, repair and operate.

pros

Of course, in addition to the listed disadvantages, all-wheel drive cars have their own unconditional advantages, the main of which is increased cross-country ability. Also, four-wheel drive cars have better dynamics, they are stable on slippery roads.

True, it should be noted that all the advantages of all-wheel drive can be obtained only if the driver fully understands the "behavior" of such a car, which is called "feel" it. In other words, a lot also depends on the professionalism of the driver, regardless of what kind of drive the car is equipped with.

Which drive is the best? Front, rear, or it may be better to give preference to a car equipped with four-wheel drive... Every car enthusiast finds himself in a similar situation when choosing a new car. There are myths about all these drives, both positive and negative - some say that it is simply impossible to drive a rear-wheel drive car in winter, others that there is nothing safer than a front-wheel drive car, etc.

To dispel such statements, which may mislead you, today we will talk with you about one such type - about all-wheel drive vehicles, in particular about the disadvantages and advantages of this type of drive.

AWD and 4WD - what is it and what is the difference between them.

Before starting an overview of this type of drive, I would like to dwell a little on terminology. 4 wheel drive cars can work in two modes - AWD and 4WD... The first mode of operation implies a four-wheel drive, which can work in constant or automatic modes. 4WD is a type of all-wheel drive that is manually engaged and disengaged. There is also another mode - four-wheel drive, which is activated as needed - which means that four-wheel drive can operate in either automatic or manual modes. The essence of the manual all-wheel drive system is that the transmission can operate in two modes. The first mode provides the transmission of the torque mode to only one axle, most often to the rear. The meaning of the second mode of the connected all-wheel drive is to transfer power to both axles, which are rigidly coupled to each other.

The all-wheel drive system, which works in automatic mode, distributes the torque evenly to both axles at all times. Often, editors of automotive magazines are confused about this issue, which misleads readers. In our article, the above terms will be often used and where it is necessary, I will make the necessary clarifications so that you do not get confused in the terminology used.

Vehicle differentials

Under differential imply a certain number of gears, the main task of which is to distribute the torque that comes from the transmission.

Modern all-wheel drive systems have three differentials that distribute power evenly to all four wheels, thus providing a comfortable turn without possible resistance. The main load rests on the center differential, as it takes torque from the gearbox and distributes it evenly between the front and rear differentials. Only all-wheel drive systems that operate in manual four-wheel drive mode are not equipped with a central differential. This is due to the discomfort experienced by the car on a dry road.

The main disadvantage differentials used in all-wheel drive technology is their possible blocking, since the behavior of the car on the road depends on it. In short, if you lose traction with at least one wheel, you risk being immobilized. This is because the differential is trying to transfer power to the axle with the least resistance. Thus, if one wheel loses traction with the road surface, all available power will be transferred to it. Since an all-wheel drive vehicle most often has to drive on bad roads, all modern cars with such a drive system have a similar lock.

Negative sides of all-wheel drive systems

It is quite difficult to drive a car equipped with this type of drive, especially in difficult road conditions, although it has collected all the positive qualities of two types of drives. Cars equipped with manual all-wheel drive most often behave on the road as rear-wheel drive. But, one cannot say so about permanent all-wheel drive systems. In the case where a front-wheel-drive car requires an increase in the amount of gas, and a rear-wheel drive, on the contrary, a decrease in fuel supply, an all-wheel drive will need both, it all depends on the quality of adhesion of the wheels to the road surface, the speed of movement and other factors.

It is very difficult to predict in advance what needs to be done at the moment. Complicating the situation is the fact that an all-wheel drive car can lose stability at one moment, without the slightest prerequisites for that. For this reason, if the car is carried to the side of the road, it can be very difficult to emerge victorious from this situation; inexperienced motorists cannot even do it.

A negative feature of all-wheel drive systems, in particular with manual control, is increased wear of parts, high noise level and increased fuel consumption compared to front-wheel drive and rear-wheel drive systems. This is due to the design of the drive system itself. Since there is a rigid connection between both axles of a vehicle equipped with permanent four-wheel drive, the four-wheel drive system can operate with a number of restrictions - it cannot be used when driving on a dry, hard road. This means that you will not be able to make the most of the thrust either.

The disadvantages of all-wheel drive systems also include the complexity and high cost of maintenance and repair. This is due to the complexity of the drive design, the presence of a large number of parts compared to other types of drives. In many ways, the make and model of the car also greatly affects the cost of maintenance.

Positive aspects of all-wheel drive systems

The main advantage of four-wheel drive vehicles is their increased cross-country ability, the ability to pull from a standstill without wheel slip, regardless of the condition of the road surface. Cars equipped with all-wheel drive systems have increased dynamics compared to other types of drives. But, be that as it may, this type of drive does not at all guarantee you that you can easily overcome this or that ford. In these situations, much depends on the professional skills of the driver, the technical condition of the tires and the car in particular.

Be that as it may, none of the above types of all-wheel drive can serve as a panacea in a particular dangerous situation. Only your professional driving skills, composure, and ability to control the situation can save you. Try to learn how to drive the car yourself, paying less attention to the type of its drive, and only then will it become predictable and manageable for you.

Think about it!

The main and invariable "character" of all four-wheel drive systems is the transfer case: a special unit that receives torque from the gearbox and distributes it to the front and rear axles. But there are several distribution methods, as well as layout schemes.

All-wheel drive systems are usually divided into three types:

Permanent four-wheel drive (Full-time)

Pros:

• reliable "indestructible" design;
• the ability to drive with all-wheel drive both off-road and on asphalt.

4Matic permanent all-wheel drive system (Mercedes-Benz)

Minuses:

• complexity compared to a hardwired drive;
• large mass;
• complexity of controllability settings;
• increased fuel consumption.

The first thing that comes to mind when there is a task to transmit torque to two axles is to rigidly connect them to the distributor with iron pipes. But here's the bad luck: when cornering, the wheels of the car go through different paths.

If the axles are rigidly connected, then some wheels will go, and some will slip. In mud, when the surface is soft, it is not scary. During the Second World War, for example, the legendary "Willis" quietly drove with rigidly connected axles, because they were operated exclusively off-road. But if the coating is hard, then these slippings will generate torsional vibrations and slowly but surely destroy the transmission.

Therefore, in the transfer case of cars with permanent all-wheel drive, there is an center differential - a mechanism that distributes power between the axles and allows them to rotate at different speeds. And if one wheel slows down, then the speed of the other increases, but the torque on it also decreases.

All this is great while we are driving on the asphalt, but what if we are stuck in a puddle with the rear axle? On the front wheels, which will stand on a solid surface, there will be momentum but there will be no revolutions, but the rear wheels will rotate very quickly, but the moment on them will be small. The power on the rear wheel will also be small and the differential will supply exactly the same power to the front. In this case, you can skid for an eternity - you still won't move.

For such cases, the differential is equipped with a lock - when it is turned on, the revolutions on all wheels are the same, and the moment depends only on the adhesion of the wheels to the road.

Due to the presence of additional nodes (differential and blocking), the entire system turns out to be quite heavy and complex. In addition, the constant transmission of torque to all wheels increases energy losses, which means worse dynamics and increased fuel consumption.

Permanent all-wheel drive is still used in the automotive industry, although recently this system is gradually being replaced by all-wheel drive on demand, which will be discussed below.

Hardwired (Part-time)

Pros:

• reliable mechanics;
• maximum simplicity with high traffic.

Minuses:

• you cannot drive on asphalt with four-wheel drive.

The differential and locks can be abandoned, provided that one of the axles is temporarily disabled. This is the logic behind the hard-wired four-wheel drive system.

The axles are connected to each other without a differential, and the moment is distributed in a strict ratio. As a result, high cross-country ability and minimum costs.

Part-time has practically died out today and is used only on purely off-road vehicles. It is inconvenient for a modern driver to use this system. The axle can only be connected when stationary, so as not to damage the mechanisms. Well, if, after pokatushek in the forest, go onto the highway and forget to turn off the four-wheel drive, then there is a risk of ruining the entire transmission.

All wheel drive with clutch

Pros:

• low cost and simplicity of the device;
• low weight;
• the ability to fine-tune the system.

Minuses:

• poor reliability and overload resistance;
• instability of characteristics.

A hard differential lock is not bad off-road, but how do you get the all-wheel drive system to dose the moment in dynamics? The degree of slipping is always different ... The solution was found in the mid-50s.

Active Torque Split AWD for Mazda CX-7 with multi-plate clutch instead of center differential

The usual mechanical differential was supplemented with a viscous clutch (viscous coupling). A viscous coupling is a part in which rows of blades connected to the input and output shafts rotate in a special fluid. The input and output shafts rotate freely relative to each other, but the secret of the clutch is precisely in the filler, which increases its viscosity with increasing temperature.

During normal movement, light turns or wheel slip, the clutch does not interfere with the mutual displacement of the blades, but as soon as the difference in the speed of rotation of the front and rear wheels grows, the liquid begins to intensively mix and heat. At the same time, it becomes viscous and blocks the movement of the blades relative to each other. The greater the difference, the higher the viscosity and blockage.

Today, clutches are used both on permanent four-wheel drive schemes in conjunction with mechanical differentials, and independently. They are connected by the driving shaft to the transfer case, and by the driven shaft to an additional axle. If necessary, when one of the axles has slipped, part of the moment goes through the clutch to it.

The further evolution of all-wheel drive systems is likely to be associated with electric motors. The first electric car with an engine on each wheel was shown at the World Exhibition in Paris in 1900 by Ferdinand Porsche. Then it was, as they would say now, "an unviable concept car." The motors were too heavy and the design was expensive. Now such a scheme has clearly more prospects.

There is also potential for a hybrid scheme, where one axle is driven by an internal combustion engine and the other by an electric motor. However, if we talk about real off-road vehicles, then no electrical innovations and friction clutches will replace cheap, simple and durable mechanics.

Further improvement of permanent all-wheel drive has led to the emergence of electronically controlled systems with the transfer and redistribution of torque.

The result of all this evolution has become systems of exchange rate stability, stabilization, traction control and torque distribution systems, which are implemented using electronics. These systems receive signals from ABS sensors that monitor the speed of each specific wheel. The more expensive and more modern a car is, the more complex schemes can be used on it: tracking the steering angle, body roll, its speed, up to the frequency of wheel vibration. The car completely collects all information about its behavior on the road, and the computer processes it and, based on this, regulates the transmission of torque to one or another axle through an electronically controlled clutch that replaced the differential.

Such all-wheel drive transmissions are called torque on-demand (literally - torque on demand). On modern high-speed cars, this is a highly noteworthy invention.

Early circuits (twenty years ago) sometimes could not behave quite adequately, there were cases with a strong delay in the actuation of the clutches (when the second bridge was suddenly connected in the turn), since at the first stage of development the clutches worked in fact. The processing speed of signals from sensors and the redistribution of torque depended on the time of these signals' passage to the brain of the machine. Modern data transmission technologies, fiber optics and powerful processors that instantly process information - all this has negated the original disadvantages. Nowadays, electronic systems have practically no serious flaws in behavior; with the addition of new sensors and new parameters, they almost always work ahead of schedule.

But there is one "but": this type of all-wheel drive transmission is suitable only for operation on asphalt with occasional minimum off-road conditions, like a moderately broken primer.

Most of the electronic clutches are not designed for off-road conditions; when they slip, they overheat and simply stop working. And for this you do not need to knead the track for half a day, ten minutes of ice drift, beloved by many, may be enough. And if you overheat it regularly, it can even fail.

Almost all systems use the brakes of the car to brake the slipping wheels, and the dirt and sand, which are inevitable on the off-road, greatly contribute to the rapid wear of the pads and brake discs, which, in addition to the cost of new spare parts, has a bad effect on the brakes themselves.

The more sophisticated the system, the more vulnerable it is, so you need to choose a car wisely, realizing that even purely urban cars, created for asphalt, are quite capable of driving onto country roads. But you need to understand which ones. Accidental breakage of one ABS sensor wire will disable the system, because it will no longer receive information from the outside. Or the fuel of not very high quality will come across - also a trip to the service, because the "lowering" may no longer turn on. Other "electronic brains" can turn off the car altogether and put it into service mode.

Cars with torque on-demand - Cadillac Escalade, Ford Explorer, Land Rover Freelander, Toyota RAV4 (after 2006), Kia Sportage (after 2004), Mitsubishi Outlander XL, Nissan Murano, Nissan X-Trail ...

In conclusion, I would like to give a simple advice: if you choose a car only for off-road, then part-time will be an excellent option. If we are talking about moving mainly in urban areas, then AWD will be quite enough. Well, permanent full is good in any situation.