Which car drive to choose - the pros and cons of different types. Which drive is better: rear, front or all-wheel drive

22.06.2019

Engine

Why do we continue to talk about car drives, today we have a global topic, namely, what is better and what to choose front or four-wheel drive for SUV or crossover? As you and I know, it is not entirely honest there, that is, it is not permanent and often does not have a hard differential lock, that is, you cannot manually lock it, it is connected only after the front axle starts to slip. And now a completely fair question arises - “is it necessary or front axle enough for the eyes? Everything is not clear here, let's understand ...

Well, to say in general — that four-wheel drive is bad, I will not! Still, I think that quite the contrary, it's even good! There are big and heavy vehicles, where he works constantly, which greatly improves cross-country ability. There is not much big cars, middle class "C", sometimes "D", where it is also constant or hard-wired (which improves both cross-country ability and handling under certain conditions), but SUVs or crossovers are completely different. All-wheel drive in them, unfortunately, has now become the property of marketers and businessmen, that is, they are trying to prove to you that they are “digging” four wheels, but in the end everything turns out completely wrong. In this article I will try to debunk all the myths, but for a better understanding, you need to talk about each type, and I think it’s worth starting from the front.

As we have already said, there are also many “copies broken” about this topic, but there the principle of talking is different, yet one driven axle is either front or rear, today the essence of the issue is different.

The front-wheel drive is very simple in structure, and it is now practically brought to perfection, that is, it can go for a very, very long time without any breakdowns.

Device :

Engine
Attached to the engine gearbox with differential, often in the same housing
From the box (differential) there are two axles with. Each side has two CV joints (inner and outer)
These CV joints fit the front wheels through special hubs.

Torque is transmitted from the engine - transmission - axles - wheels. This is how it is given front wheel drive car in motion.

It is worth noting that transmission fluids there is not much here, that’s all in the box itself, as a rule, the rest of the joints are dry (well, or almost dry, there is grease under the anthers in the CV joints, but there it’s really minuscule and it doesn’t change). This tells us that you can not follow this design at all. Of course, I still advise you, because if they break, the hinge will soon fail, but believe me, for the next 70 - 80,000 km, this can not be done. If the manufacturer is serious, then anthers can walk 150 - 200,000 km.

The rear suspension in the front drive does not carry any semantic load, that is, it is a banal “support for the wheels”, there is practically no weight, it is light here (either a beam or a “multi-link”). And last but not least, the rear end requires virtually no maintenance, well, if only the brake pads are changed.

Four-wheel drive

Even a plug-in all-wheel drive through a viscous coupling has a much more complex structure (I'm already silent about the permanent ones). There are more parts that spin (most of the time) at idle, there are already two bridges, not one, also appear cardan shaft and the rear axle is no longer secondary.

Device :

Engine
A gearbox that can be combined with a front differential. However, the front differential can be taken out separately
Front axle with CV joints for front wheels
Center differential, it can also be in the same housing with the box, but it can be separate (it all depends on the design)
Transfer case.
Rear cardan to transmit torque to the rear axle
Visco coupling or electro coupling (hydromechanical) for automatic connection of the rear axle
Rear axle. It can be made in a molded case, from which two axle shafts go to the rear wheels. But now often two axles with CV joints also go from the rear differential, by analogy with the front axle.

As you can see, the structure is much more complex! Two more differentials appear here, center and rear, there is also a transfer case, viscous couplings and more. All this adds to the weight of the car at least 100 kg, and possibly more. There are also a lot of parts that "spin" in the oil, and they really need to be monitored. Some manufacturers recommend changing them transmission oil. If any oil seal leaks, the whole assembly may fail. I think everyone understands this, but again, everyone thinks since I have all-wheel drive, then I’m on some SUV or crossover, on a RAV4 or the same Duster, I’ll just become an off-road conqueror - “what do I need an UAZ, I myself am like an UAZ” ! BUT is it really?

Four-wheel drive through a viscous coupling (electric coupling, hydromechanical coupling)

Well, here we come to the most interesting thing, for whom is the all-wheel drive of such crossovers, where can it be used? For many, this means that you can immediately go to the forest for mushrooms and berries, that you can fight such impassability, that, as they say, “on the door”! Guys, stop, all-wheel drive on crossovers and SUVs is very conditional, I would even say “urban” it is not intended for serious off-road tests.

Why? Yeah, it's just not designed for it. Often, on many crossovers, it is connected through a viscous coupling or an electric coupling.

viscous coupling , we have already talked about it (you can in detail). Transmits torque through special liquid enclosed in the viscous coupling housing. When one axle begins to slip, the fluid quickly hardens, thereby closing the rear axle and connecting it. The disadvantages of such a drive are that it is almost impossible to turn it on yourself or block it rear differential to work. ONLY AFTER SLIP. Therefore, the efficiency of such a full drive is quite low.

As it becomes clear, the work is a little different. There is no special liquid here, but there are electromagnets that close or open the disks when voltage is applied to them, thereby connecting or disconnecting the all-wheel drive. This clutch is dry, there are no oils in it, which is both good and bad. The good thing is that you do not need to monitor the leakage of seals and change the fluid. Bad - this clutch overheats quickly. The connection of the four-wheel drive occurs after the front-wheel drive slips, usually after the second rotation front wheel. In some vehicles equipped with such a node, there is forced blocking, that is, you can physically block the rear axle. It seems that here it is the DECISION, the control is much better than that of the viscous coupling, HOWEVER, THERE IS A BIG FLY IN THE OIL. Such a drive overheats very quickly and turns off, if you can slip for a long time on a viscous coupling, then here electromagnetic clutch, will turn off after 3 - 5 minutes of slippage. They also fail faster due to high temperatures, as the experts say - they just burn.

Hydromechanical clutch. Very similar design with the electromagnetic version. However, here the discs are closed due to oil pressure. Inside there is a pump that creates pressure to compress or unclench them. The pumps are now also available with electric drive, used to be mechanical.

In fact, such structures are used in in large numbers crossovers or SUVs, it’s very, very difficult to find another here.

Full or front?

As you can see, to call such all-wheel drive - COMPLETE, somehow the tongue does not turn! What are they made for. You know, I once talked with a “hardened” mechanic about such automatic connections, and this is what he told me - “poking into even (medium dirt) on such machines will be unprofitable, they are simply not designed for this off-road, do not think that you bought a car with cross-country ability similar to our UAZ, THESE ARE DIFFERENT CLASSES! Especially if you have automatic transmission gears, because it can also overheat quite quickly (everything is a little better with mechanics). These cars are designed to deal with a snow-covered yard in the city in winter, or with a couple of shallow puddles on the way to the country house"

You know this like a shovel in your trunk or a neighbor is a passenger - what do I mean? On a front-wheel drive car, you will need to clear the rut in front a little (with a shovel), or ask a passenger next door to give you a little push. But such a plug-in all-wheel drive car will be able to get out by itself. Fine? Of course yes! But is it worth paying extra for it?

If you disassemble the front and full options, you should think about where and how you move? It is also worth considering that an all-wheel drive vehicle:

Costs more.
Complete sets with all-wheel drive are at least "medium" and "top", that is, you will not find it in the "standard".
The car weighs more
More vibrations. Because more knots are spinning.
Service costs more
More rotating elements, which reduces the resource
More fuel consumption
The modest capabilities of this all-wheel drive car

Actually, if you are a 100% city dweller, the snow is removed in the cities, you go to the country house where there are several meters of dirt that are not quite comfortable - THEN TAKE SUCH ALL-WHEEL DRIVE, AS I THINK THIS IS OVERPAID, AND IT IS NOT NEEDED!

Although, in fact, there are 4 main types of drive - all-wheel drive is usually divided into 4-wheel drive and all-wheel drive (when the car has more than two axles).

Which of these drive options is better: full, front or rear, depends on the driving style, the nature and surface of the road on which to drive, the type of car itself (it is a sports car or a full-fledged SUV) and a number of other conditions. But what type of drive is right for you, what are the differences between rear, front and all-wheel drive and how they all work. Let's look at the differences between these types of drive separately, and at the end we give a general table with the pros and cons of each type.

Front-wheel drive

The bulk of cars in our country, and in most countries of the world, produced since the late 1990s, use front-wheel drive. First of all, this is due to the space efficiency of the front-wheel drive, its relative cheapness. The car's front-wheel drive ensures that the engine, transmission and power train are located in one compact housing that is conveniently located under the hood, freeing up the rest useful part vehicle for passengers and cargo.

Front-wheel drive

This allows, of course, to offer more inner space while maintaining the compactness and budget of the machine. Almost all front wheel drive vehicles have motors mounted across the length of the machine - thus the torsion of the engine is transferred to the torsion of the wheels as compactly as possible - with less extra details, gearboxes and more.

Pros of front wheel drive:

Front-wheel drive has additional advantages in snow and rain: the weight of the engine directly over the drive wheels gives the car better grip on slippery roads. Thus, a front-wheel drive car is much less prone to skidding, and the critical speed at which the car will begin to skid is higher than that of rear wheel drive car other things being equal. This is perhaps the main advantage of front-wheel drive.
Compactness. As mentioned above, the location of the engine next to the drive wheels greatly simplifies the design of the machine and gives much more free space both under the hood and in the cabin and under the bottom.
Compactness determines budget - a front-wheel drive car is also much cheaper to design and build than a rear-wheel drive and, all the more, all-wheel drive.

Cons of front wheel drive:

Although, despite the fact that the front-wheel drive car is less prone to skidding rear axle, if front wheel drive car led into a skid, then the car is much more difficult to get out of this skid due to the same design.
And more about skidding - if you remember the driving school course, then when skidding the rear axle on the front drive, you should increase the gas supply to get out of the skid. And this is instinctively impossible for some drivers. The thing is that in an emergency panic situation, many drivers - especially inexperienced ones - press the brakes, which is not acceptable for front wheel drive car and only exacerbates the skid.
Since the drive wheels are also swivel, this introduces its own limitations, firstly, on maximum angle the rotation of the wheels, and the wear of an increased number of mechanisms - first of all, the so-called "grenade", which provides drive to the turned wheels.
Since the main components are located under the hood in front of the car, the front-wheel drive makes its own adjustments to wear. brake mechanisms. The fact is that when braking, the main weight of the car is transferred forward (when moving forward, of course). This means that the already heavy front of the car works out braking even more, which leads to significantly more rapid wear brake mechanisms on the front axle of the machine - first of all, brake pads. Often the rear pads are changed when the front pads have already been replaced twice.
For the same reason that the weight is transferred forward, on the contrary, when the car accelerates, its weight is transferred to the rear wheels, which determines worst grip with the road leading the front wheels. Thus, we get that the front-wheel drive is more prone to slipping, which is on charged powerful cars is just a tragedy. That is why most sports cars- rear-wheel drive.

Rear drive

Rear drive most often means that the engine in front, located longitudinally along the length of the car, sends its torque to the rear wheels through a long driveshaft. Meanwhile, the most simplistic components of rear-wheel drive make it generally cheaper than front-wheel drive, contrary to the statement in the pros of front-wheel drive above, however, if you include everything high tech in modern rear-wheel drive, such cars end up being much more expensive.

Rear drive

In the past, almost all cars were rear-wheel drive for a long time, because it seemed like a very simple design due to the fact that mechanics and vehicle designers had even a vague idea of how to equip a car with front-wheel drive and still leave the front wheels turning.

Rear wheel drive advantages:

Rear-wheel drive has its main key advantage - performance. Since during acceleration of the car, inertia transfers a significant proportion of its (car) weight to the rear wheels, which are the driving ones, the likelihood of their slipping is much less than in the case of front-wheel drive. That's why most sports cars, such as Chevrolet Corvette, Ferrari, Lamborghini, muscle cars like Dodge Challenger, performance sedans such as the BMW 3 Series, and large luxury cars, such as Mercedes-Benz S-class use rear wheel drive.
In front-wheel drive, one set of wheels provides both movement and control of the machine. Rear-wheel drive allows these duties to be shared between the front and rear wheels, while spreading heavy mechanical components along the entire length of the car allows its weight to be distributed more evenly between the front and rear wheels. better handling.
Despite the fact that the rear-wheel drive skids easier slippery road, it is the rear-wheel drive that is also easier to get out of the skid, for which in the overwhelming majority of cases it is enough to simply stop transmitting the drive to them, but, on the contrary, release the gas pedal and let the engine speed slow down the rear axle.
Since the front wheels are not simultaneously driving, the simplicity of the design allows them to turn at a larger angle, which reduces the overall turning radius of the machine.
Drift - of course, where without this plus! It is the rear-wheel drive that provides such an opportunity, thanks to the slipping rear wheels and turning the front ones.

Rear wheel drive cons:

The main disadvantage is that front-engined rear-wheel drive requires a transmission "tunnel" that runs through the center of the car, taking up valuable interior space, although this is of lesser importance in larger vehicles.
Rear wheel drive may also be less desirable for driving in rain and snow. The thing is that since it is the rear axle that is more prone to skidding when cornering, the drive to these rear wheels makes them slip more on slippery roads, which only increases the likelihood of skidding. Therefore, in theory, rear-wheel drive is easier to skid (this is why drifting is only possible on rear-wheel drive). Although currently electronic stability control systems (ESP) perfectly eliminate this problem, although not completely.
Another significant disadvantage of rear-wheel drive is that when cornering, more effort is required from the engine, because the rear wheels push the car forward, while the front wheels are turned to the side, due to which a little power is lost.

By the way, not all rear wheel drive vehicles have an engine in front. Some high performance machines have the engine in the middle or at the rear. These cars include Ferrari, Lamborghini and other cars. And, of course, it would be crazy to put the engine in the middle or rear in such cars, while they would be front-wheel drive.

Rear wheel drive with mid-engine engine layout

Meanwhile, almost all trucks are equipped with rear-wheel drive, since when they are loaded, the bulk also falls on back, which reduces the possibility of slipping of the drive wheels.

Four-wheel drive

Technically, all-wheel drive can be divided into three subgroups: permanent all-wheel drive, plug-in all-wheel drive, and adaptive all-wheel drive. All of these systems have the ability to deliver power to all four wheels of a vehicle, which improves traction in bad weather and over rough terrain, and are more commonly found on off-road vehicles such as the Jeep Wrangler and Toyota Land cruiser. All types of all-wheel drive also offer much better traction, allowing the car to enter tight corners at higher speeds, so you can find all-wheel drive performance sedans in the catalogs, such as the Audi RS7, for example.

All-wheel drive (with gearbox or automatic all-wheel drive system)

Adaptive all-wheel drive most commonly found on SUVs, crossovers, and sports cars (and some family cars and minivans). This system can transfer power from the engine between the front and rear wheels as needed. Moreover, most SUVs transfer 100% of engine power to the front wheels; but when they start to lose traction (on slippery roads, for example), power starts shifting to the rear wheels as well. Moreover, power distribution does not always occur in 50/50 shares, although it is close to this value.

Plug-in all-wheel drive- This is the simplest type of all-wheel drive, which is implemented on SUVs such as Jeep Wrangler, Ford F-150 and good old Niva. These systems have a device called transfer gearbox, which allows the front axle to be connected (or, conversely, disconnected from the transmission manually). Most of the time, the car is driven in rear-wheel drive mode; but when more traction is needed, the driver manually switches to four wheels using a special lever.

Permanent four-wheel drive. In such an all-wheel drive system, all wheels are constantly pulling force from the engine. Today, this system is rarely installed on modern cars.

Advantages of all-wheel drive

Of course, the main advantage of all-wheel drive is cross-country ability.
Much better handling, which allows you to enter corners faster and feel more confident on slippery roads.

Cons of all-wheel drive

The main disadvantage of all all-wheel drive systems is their additional mechanical complexity and, as a result, the high cost of production and design.
All 4x4 vehicles tend to be less fuel efficient as they require more than 2x more wheels compared to front or rear-wheel drive, but also various kinds of gearboxes and shafts.
Tires all-wheel drive cars all four are already erased, and not a pair.

What is best for you?

The vast majority of cars (and, believe it or not, many crossovers) are front-wheel drive. This suitable choice for most drivers as it provides good grip with the road in bad weather and decent interior space.

If you're a sports car fan or live in a place where the weather is usually good, you're advised to consider rear-wheel drive. There are plenty of good front wheel drive sports cars out there though (like the Volkswagen GTI).

If you live where it rains and there is a lot of snow, where most of the roads are dirt or off-road, then an all-wheel drive SUV is your choice. Many rear wheel drive premium sedans offered in all-wheel drive versions, as well as many crossovers and SUVs can basic modifications have front or rear-wheel drive, and in more expensive ones - all-wheel drive.

Which is better: rear, front or all-wheel drive - comparison table

Let's look at the gradation of ratings (bad, satisfactorily, good , excellent ) various sides and characteristics of full, rear and front wheel drive.

Conditions	Front-wheel drive	Rear drive	Four-wheel drive
Budget car	Great	Fine	Badly
Handling on dry roads	Great	Great	Great
Handling on slippery roads	Fine	Satisfactorily	Great
Traction on eroded clay, snow	Satisfactorily	Satisfactorily	Great
Behavior on powerful cars	Badly	Fine	Great
The complexity of the design, the total weight of the system	Great	Satisfactorily	Badly
Braking efficiency	Satisfactorily	Great	Great
Maneuverability	Satisfactorily	Great	Satisfactorily
Loss of power (consequently, increased fuel consumption)	Great	Satisfactorily	Badly

Four-wheel drive: features, pros and cons of designs

A person began to use a vehicle with all-wheel drive long before the appearance of a car - it was a horse. Big ground clearance, intelligent system all-wheel drive - all this was ingeniously implemented by nature. In order to repeat this in technology, a person needed a lot of effort, means, and most importantly, time. However, these years were not wasted. Consider the features existing types all-wheel drive cars, as well as their pros and cons.

text: Oleg Slavin / 03/29/2017

A LITTLE HISTORY

The first vehicle with all-wheel drive appeared almost two hundred years ago. English engineers Timothy Burstall and John Hill built an omnibus in 1824 with all four wheels turning at the same time. Another 59 years passed before the already American engineer Emmet Bandelier patented his all-wheel drive system. In his vehicle some kind of differential distributed thrust from steam engine between front and rear axle. And only in 1903 did the first all-wheel drive vehicle. They became the Spyker 60 HP, created by the Dutch for racing: the car was equipped with as many as three differentials.

Consider the types of all-wheel drive and its differences.

PLUG-IN ALL-WHEEL DRIVE (PART-TIME)

Today it is the cheapest, but at the same time requiring a thoughtful approach to use, the type of drive. Its principle of operation is simple and consists in the rigid connection of the front axle. It is the absence of a differential between the axles that makes this type of drive simple, because the bridge is connected by means of a simple mechanical clutch. As a result, the engagement is rigid, and the distribution of torque between the axles is the same. It is this same distribution of torque that imposes certain restrictions on the use of this type of all-wheel drive system on asphalt. The first thing you will feel if you decide to use such an all-wheel drive on paved roads is a decrease in handling. It will become noticeably worse to pass turns due to the lack of difference in the length of the path of the bridges. The second point that awaits those who neglect the warnings in the instructions for using the all-wheel drive, and such cars definitely have them, is the increased load on the transmission and, as a result, its quick failure. And the third point - increased wear tires. In this regard, include a similar drive on vehicles that do not have center differential, it is possible only on off-road, where the lack of a differential is compensated by the possibility of wheel slippage. Despite the archaic design, there are plenty of cars with such an implementation of all-wheel drive. Typically, this is either military equipment, or inveterate SUVs, such as UAZ, Toyota Land cruiser 70, Nissan Patrol, Suzuki Jimny, pickups ford ranger, Nissan Navara, Mazda BT-50, Nissan NP300. Being exclusively rear-wheel drive vehicles on asphalt, they can still afford to connect the front axle on off-road and thereby significantly increase cross-country ability. In general, cheap and cheerful.

AUTOMATICALLY CONNECTED ALL-WHEEL DRIVE (TORQUE-ON-DEMAND)

This kind of all-wheel drive system has actually become the next stage of evolution. Just like in Part-Time, the second bridge is connected here on demand, but this time the driver's desire is the requirement (to do this, just press the appropriate button in the car), or it happens automatically. The connection of the second axle is carried out in case of slippage of the wheels of the main drive axle. As a rule, with such a scheme, the front axle is the main drive axle. It was possible to implement such a design due to the center clutch. That is, in this design there is no differential, as before, however, a hydraulic or electromagnetic clutch allows axle slippage, and this improves the vehicle's handling in all-wheel drive mode. This system also has one very big disadvantage- Coupling overheating. The fact is that all clutches, whether hydraulic or electromagnetic, provide axle slippage due to friction, which generates heat. This very heat often causes the coupling to overheat and, as a result, the transmission of torque to the best case, and as the worst option - its complete failure. Better resist overheating electro-hydraulic clutches, which are successfully used on their crossovers Nissan. However, they are also characterized by overheating, in connection with which hard off-road conditions are, of course, contraindicated for such crossovers. And the electro-hydraulic clutch, unlike the hydraulic one, is able to close or open on command from the control unit or at the request of the driver using the very button mentioned above. That is, by blocking the clutch in advance, a difficult section of the road can be overcome much more comfortably, but you need to remember that turning on a hard block on asphalt on such cars is also not welcome. Not without reason, to protect against a fool, most systems provide automatic unlock in case of exceeding the speed determined as safe for this mode of movement. There are quite a lot of cars using this type of all-wheel drive in their off-road arsenal. As a rule, these are light SUVs of the type Renault Duster, Nissan Terrano, Mitsubishi Outlander, Toyota RAV4, Kia Sportage etc.

PERMANENT ALL-WHEEL DRIVE (FULL-TIME)

This is one of the most advanced and at the same time the most expensive species all-wheel drive vehicles. Like permanent drive due to the presence of that very center differential, as well as interwheel ones, it’s quite expensive pleasure, both in terms of production and in terms of operation and maintenance. In addition, this type of drive, in addition to the center differential, must also have a mechanism for blocking it. For what? It is enough to recall the principle of operation of the differential, as it becomes clear that if at least one wheel starts to slip, then all the torque will immediately begin to be transferred to it, and why then was it worth fencing the garden? On the other hand, if you provide the possibility of blocking both the inter-axle and inter-axle differentials, then the car's cross-country ability increases many times over. As a rule, such four-wheel drive control schemes can only be accessed on expensive SUVs. For example, a phased locking of all differentials is available on a very expensive Mercedes-Benz Gelendewagen.

Found a permanent all-wheel drive and its application on road cars. In particular, most manufacturers use them as an expensive option that provides the machine with exceptional stability and excellent dynamic characteristics. However, it should be understood that no one has repealed the laws of physics, and no matter how stable an all-wheel drive car is on straight lines and in turns, neglect common sense do not do it. Yes, and the control methods of such machines are somewhat different from those used on front- or rear-wheel drive models. To somewhat offset this feature, most manufacturers deliberately distribute the torque along the axes not equally, but in proportion. For example, most Mercedes-Benz with the 4Motion badge have a 30/70 torque distribution to give the car a classic rear-wheel drive character. There are options for all-wheel drive, which are sharpened exclusively for handling. So, the Honda SH-AWD (SH - Super Handling) permanent all-wheel drive system can distribute torque not only between the front and rear axles, but also between the left and right rear wheels. That is, in a turn, up to 70% of the moment can be transferred to the external rear wheel, which literally pushes the car into a turn.

Hybrid all wheel drive

The name of this type of all-wheel drive speaks for itself. Here, for traction on all wheels, two different engines. As a rule, the engine drives the front axle. internal combustion, and the electric motor provides the rear axle with torque. Such a system is quite simple in terms of implementation, because neither a center differential nor a cardan shaft is required. However, as practice has shown, this type of drive is still more suitable for road cars, not SUVs. In extreme cases, such a drive can be implemented on a crossover, which is not designed for constant war with off-road. Which, in fact, is practiced by manufacturers. Suffice it to recall Lexus RX450h, Toyota RAV4h, Peugeot 508 RXh. Electric motors mounted on the rear axle can improve vehicle handling, increase the efficiency of the main engines and only slightly improve cross-country ability. Which, in principle, is quite enough to get out of a snowdrift or overcome an insignificant obstacle.

The number of all kinds of SUVs and crossovers on our roads is growing at a tremendous pace. One of the main advantages of such cars is the all-wheel drive system, the principle of operation of which is different models can differ significantly. All types of all-wheel drive can be divided into three main types: temporarily connected (Part Time), permanent ( full time) and automatically connected (On Demand Full Time).

Temporarily connected all-wheel drive Temporary all-wheel drive, or as it is often called Part Time, does not allow you to drive in all-wheel drive for a long time. In this type of all-wheel drive, there is no center differential that would compensate for the difference in the speed of rotation of the front and rear axles. Without it, when driving on a dry road, transmission parts begin to wear out quickly. The Part Time all-wheel drive can only be forcibly connected to overcome a difficult section of the road at low speed. Usually, a lever is used to connect transfer box transmission. Although in some versions to connect front axle you need to get out of the car and turn the special handles (hubs) on the front wheel hubs.

In addition, a car with automatically connected all-wheel drive can be turned into a purely front-wheel drive, without any connections. Again, using the "magic" button (2WD, etc.). Disabling all-wheel drive helps save fuel, and the need for four-wheel drive in the city does not often arise. Automatic all-wheel drive is the "youngest" of the 4x4 systems. They are equipped with the vast majority of crossovers in our market. You can even say that such a drive is an essential attribute of a real crossover. New type of car demanded new type all-wheel drive, everything is logical.

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Which drive is fuller? It is rather difficult to determine which all-wheel drive is the most optimal, since each of them has its own advantages and disadvantages. On serious off-road, off-road vehicles with temporarily connected all-wheel drive and hard mechanical interlocks all differentials (interaxle and interwheel). But in urban conditions, such cars do not give any pleasure from driving. In turn, purely urban crossovers with their automatically connected all-wheel drive are practically helpless on any off-road, but they are controlled like ordinary cars. he won’t let himself be offended on the highway. But such a drive will not interfere with his work, that is, neither save fuel nor after a very difficult area drive (despite the "very smart" electronics) may not work.

Temporarily connected all-wheel drive

Temporary all-wheel drive, or as it is often called Part Time, does not allow you to drive in all-wheel drive for a long time. In this type of all-wheel drive, there is no center differential that would compensate for the difference in the speed of rotation of the front and rear axles. Without it, when driving on a dry road, transmission parts begin to wear out quickly.

All-wheel drive Part Time can only be forcibly connected to overcome a difficult section of the road at low speed.

Usually, a transfer case lever is used to connect. Although in some versions, in order to connect the front axle, you need to get out of the car and turn special handles (hubs) on the front wheel hubs.

Only “full-fledged” SUVs that are used for their intended purpose are equipped with temporarily connected all-wheel drive. Outstanding representatives such "rogues" can be called and who are in no hurry to give control of all-wheel drive to electronic "brains".

In addition, “temporary” all-wheel drive is equipped with almost all Chinese copies famous SUVs 90s.

Real SUVs with "fair" Part Tim modee are slowly fading into history as more modern all-wheel drive systems replace them.

Permanent four-wheel drive

Permanent four-wheel drive, or FullTime, most manufacturers do not allow you to force disconnect / connect one of the bridges.

Due to the presence of a center differential, such a transmission constantly (in any conditions) operates in all-wheel drive mode. Moreover, in modern models the center "diff" has its own electronic "brains".

With such a differential, the torque can be transmitted to the axles in different proportions, that is, not only 50/50. When slippage occurs, the “smart” differential can instantly “transfer” torque not only to the axle with better grip, but even on a separate wheel, which has something to catch on.

This type of all-wheel drive is the most "advanced" among other 4x4 systems.

The abundance of "smart" electronics on the most modern systems allows the car to adapt even to a specific pavement(asphalt, gravel, sand, etc.), the driver only needs to press the desired button.

The most famous representatives of permanent all-wheel drive is a company with a proprietary Quattro system, and Subaru with AWD system (All wheel drive).

Interestingly, this type of transmission is equipped with completely “non-off-road” sedans, coupes and hatchbacks. This highlights the versatility of this all-wheel drive system.

Automatic all-wheel drive

Automatically connected all-wheel drive (On Demand Full Time) allows the car to remain front-wheel drive and only in the event of slipping of the drive wheels connects rear axle. Automatic connection all-wheel drive in modern systems occurs almost instantly at the first sign of slipping.

Depending on the capabilities of a particular system, the torque between the axles can be redistributed in any proportion (from 10/90 to 90/10).

Wherein electronic system stabilization (ESP) allows you to maintain control of the car, which can suddenly change from front-wheel drive to rear-wheel drive, and vice versa.

To overcome a particularly difficult section of the road, this type of drive (in most versions) makes it possible to forcibly redistribute the “floating” torque between the axles in a 50/50 ratio. Usually there is a button for this that says 50/50, Lock, etc. But when a certain speed is reached (40-50 km / h), the blocking will turn off, and the system will return to the “floating mode”.

Automatic all-wheel drive is the "youngest" of the 4x4 systems.

They are equipped with the vast majority of crossovers in our market. You can even say that such a drive is an essential attribute of a real crossover. A new type of car required a new type of all-wheel drive, everything is logical.

Which drive is full her?

It is rather difficult to determine which all-wheel drive is the most optimal, since each of them has its own advantages and disadvantages.

On serious off-road, off-road vehicles with temporarily connected all-wheel drive and hard mechanical locks of all differentials (interaxle and interwheel) will feel best. But in urban conditions, such cars do not give any pleasure from driving.

In turn, purely urban crossovers with their automatically connected all-wheel drive are practically helpless on any off-road, but they are controlled like ordinary cars.

The golden mean is permanent all-wheel drive, which will master off-road and will not give offense on the track.

But such a drive will not interfere with its work, that is, it may not be possible to save fuel or drive through a very difficult section (despite the “very smart” electronics).