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 is the system exchange rate stability, stabilization, traction control and torque distribution systems that are implemented electronically. These systems receive signals from ABS sensors that monitor the speed of each individual wheel. The more expensive and more modern car, the more complex schemes can be used on it: tracking the steering angle, rolls of the car body, its speed, up to the frequency of vibration of the wheels. The car completely collects all the 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 invention is very noteworthy.
Early schemes (twenty years ago) could sometimes behave not quite adequately, there were cases with a strong delay in the operation of the clutches (when the second axle was suddenly connected in the turn), because at the first stage of development, the clutches worked in fact. The speed of signal processing from sensors and the redistribution of torque depended on the time it took for these signals to reach the brain of the machine. Modern technologies data transmission, optical fiber and powerful processors that process information instantly - all this has negated the initial shortcomings. Now electronic systems practically do not have serious flaws in behavior, with the addition of new sensors and new parameters, they almost always work ahead of the curve.
But there is one “but”: this type of all-wheel drive transmission is suitable only for operation on asphalt with episodic minimal off-road like moderately broken primer.
Most electronic clutches are not designed for off-road use; when slipping, they overheat and simply stop working. Moreover, 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 completely fail.
Almost all systems use brake mechanisms machines for braking slipping wheels, and dirt and sand, inevitable on the roads, greatly contribute to the rapid wear of 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, designed for asphalt, quite allow exits to country roads. But you need to understand which ones. An accidental break in one wire of the ABS sensor will disable the system, because it will no longer receive information from the outside. Or fuel of not very high quality will come across - also a trip to the service, because the “lower” may no longer turn on. Other "electronic brains" can generally turn off the machine and put it into service mode.
Vehicles with torque on-demand - Cadillac Escalade, Ford Explorer, Land Rover Freelander, Toyota RAV4 (after 2006 onwards), Kia Sportage(after 2004 onwards), 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 become great option. If we are talking about movements mainly in the city, then AWD will be quite enough. Well, a permanent full is good in any situation.
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 all-wheel drive for an 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 is the 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 large and heavy cars where he works all the time, which greatly improves cross-country ability. There are also not very large 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 a front-wheel drive car is driven.
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 importantly, the rear end is virtually maintenance-free, well, unless brake pads change.
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 rear axle 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 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 are "spinning" in 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 that 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 lock the 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. All-wheel drive is connected after front-wheel drive slips, usually after the second rotation front wheel. In some cars equipped with such a node, there is a forced lock, that is, you can physically lock 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 the viscous coupling, then the electromagnetic clutch will turn off after 3-5 minutes of slipping. 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. Pumps can now also be electrically driven, before it was mechanical.
Actually, such designs are used on a large number of crossovers or SUVs, it is 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 expensive, they are simply not designed for this off-road, do not think that you bought a car similar to our UAZ in cross-country ability, 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 do 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!
If you are a resident of the countryside, you have only seen asphalt on TV, and the snow fills up so that it is difficult to move on a tractor - IT WILL NOT HELP YOU ALSO! Here you need to look at a more brutal technique, possibly on a frame. YES, at least the same UAZ will be more practical.
All-wheel drive for crossovers and SUVs, this is not quite what you expect - BELIEVE IT. This is more of a marketing trick, rather than an all-wheel drive car in the sense of an “off-road conqueror”. Of course, there are benefits from it (for example, you live near the city, in winter they seem to clean the roads, but not always), but it is so insignificant that it is POSSIBLE to give 100 - 200,000 rubles more, as I think. YES, and to serve such a car is EXPENSIVE! Given all the pluses and minuses, then personally I would not buy! Although you may have other thoughts, write in the comments.
Now a short video.
Hello dear blog readers website. In today's conversation with you, let's try to choose car drive and find out which drive is better: front, rear or full? Vehicle drive- this is one of its most important characteristics, therefore, before deciding, which drive to choose, it is necessary to understand what types of car drives differ from each other.
Plan for choosing a car drive:
What kind of drive: front, rear or all-wheel drive?
Vehicle drive determines to which wheels the thrust of its engine is transmitted. All modern passenger cars have four wheels each - two front and two rear, while the engine power of the car can be transmitted either to all four wheels or to one pair of wheels - anterior or back. How are they different from each other front, rear and all-wheel drive?
Which drive is safer? Which drive is the safest?
It is much easier to drive, a front-wheel drive car is more difficult to skid, so as first car it is better to choose a car front wheel drive. On the other hand, the drift rear wheel drive car easily corrected by an intuitive release of gas - let go of the gas and the car returned to the trajectory. And on front wheel drive skid means that the driver has crossed all permissible limits. Here is a small example.
Call skid on front wheel drive car more difficult than in the rear, but also to get out of a skid on front wheel drive Much more skill is required. On rear wheel drive, skidding is the norm and it occurs constantly, and in order to eliminate it, it is usually enough to simply release the gas pedal. It can be said that rear drive immediately shows the driver all the danger of a slippery road, and the front one hides it from the driver to the last. However, even for rear wheel drive there is a speed limit beyond which releasing the gas will not be able to stabilize the car. See how a rear-wheel drive car can skid.
Concerning all-wheel drive then with him still more difficult. Four-wheel drive on slippery surfaces can behave like front or like rear, depending on which wheel is slippery. Let's look at an example the most popular model Chevrolet Niva how permanent four-wheel drive can behave, not equipped ESP system . This once again confirms that four-wheel drive only increases patency And improves acceleration dynamics but not at all does not improve handling.
And in this video, at a speed of 150 km / h, Audi car, equipped Quattro permanent all-wheel drive, falls into an oil puddle and breaks into a skid. Only rich experience and steel nerves of the pilot allow him to get out of the water dry and unharmed.
For front wheel drive more high directional stability than the rear. On snowy or muddy roads front-wheel drive goes like a locomotive on rails, while rear wheel drive it is necessary to work with gas on a slippery road very carefully - the car can turn around.
And here four-wheel drive snow porridge, like off-road, tolerates even better than the front, but if not center differential, then he enters the turn reluctantly. Be careful!
It allows you to accelerate faster, easily enters a skid, but also easily gets out of it, and all this together makes driving a rear-wheel drive car more interesting. On a slippery road rear drive it is not controlled at all like the front one, but many drivers appreciate it for this. In general, if safety is not in last place for you, and you want to not only drive a car, but be able to drive it in any situation, then be sure to watch this video from main road:
So, which drive is considered safer? Alas, but it is impossible to answer this question unequivocally. Every kind of car drive behaves differently, each has its pros and cons, each drive type must be skillfully used without violating the laws of physics. But one thing is for sure: if you need safe car , then it can have any type of drive, the main thing is that it must be turned on stability control system - ESP. This smartest program is able to slow down each wheel separately, thus correcting many of the driver's mistakes.
Which drive is the most passable?
Really, at front wheel drive patency is slightly higher than that of the rear and there are at least two reasons for this. Firstly, driving wheels at front wheel drive pressed to the ground by the weight of the engine which reduces slippage. Secondly, driving wheels at the front drive are helmsmen, and this allows the driver to set the direction of thrust.
In the event of slipping of the drive wheels, the driver of a front- or all-wheel drive car can pull the car out of the snow captivity with the front wheels, while rear wheels follow strictly behind the front ones. The rear-wheel drive in such a situation behaves worse - the rear starts to demolish to control this process is very difficult.
, on a slippery slope climbs more confidently than rear. The drive front wheels are slipping, but pulling the car to the top, and rear drive, in such a situation, it stalls and strives to turn the car around. The king of slippery slopes is undoubtedly his majesty four-wheel drive, which climbs an icy slope without slipping.
And yet, driving around in winter on slippery roads, you can’t rely only on all-wheel drive, because its possibilities are not unlimited. With studded tires, you can climb a slippery winter slope on any drive, especially if the machine is equipped with anti-slip system ESP.
So, the most passable, of course, is all-wheel drive. Rear-wheel drive is the least suitable for off-road assault, but it’s better not to move out of a hard surface on a front-wheel drive.
Suitable for you if you do not plan to leave the paved roads. If you are sometimes going to make risky forays into the fields, then you need to take at least a car front wheel drive, and for serious off-road forays you will need a car equipped with all-wheel drive.
On dry pavement rear drive accelerates faster than the front. During acceleration, the weight of the car is transferred to the rear axle, while the front wheels are unloaded, which is why front-wheel drive during acceleration allows strong slippage. But the fastest car accelerates with all-wheel drive Naturally, for this it must be equipped with a powerful engine.
So, if you need a car that accelerates faster than others, then you need to choose a car with rear, but better with all-wheel drive and as powerful a motor as possible.
Which drive is better? Front or rear wheel drive?
outperforms the rear by such an indicator as fuel consumption. Average, front wheel drive is more economical rear, and the difference can reach 7%. And here four-wheel drive, in terms of efficiency, takes an honorable third place - it the most voracious, largely because of this, most motorists choose exactly front or rear wheel drive.
In rear wheel drive cars, the front wheels do not have drive shafts, so maximum angles steering wheels, rear-wheel drive, more, eh turning radius is smaller, which is very useful in the city.
Front wheel drive is cheaper to manufacture rear, so front-wheel drive cars are sold for more affordable prices. More low price - this is the main advantage of front-wheel drive over rear and all-wheel drive. It is thanks to the low price that front-wheel drive has won the place of the most common of all types of drive: more front-wheel drive cars are being produced than with rear and all-wheel drive combined. The second reason for the high popularity front wheel drive is simplicity its use on a slippery road, its low demands on the skill of the driver.
If choose front or rear wheel drive, then in most cases front wheel drive is the best option . It is more affordable, more economical, simpler in design and less demanding on the skill of the pilot. - Your option if you already have a decent experience behind you, and now you want to not just drive a car, but enjoy from the process of driving.
Which car drive is better?
So, we need to sum up. If everything is greatly simplified, then the conclusion can be drawn as follows: the best type of drive is all-wheel drive working in tandem with ESP stability control. However, all-wheel drive more expensive to buy and expensive to maintain, yes and consumes a lot of fuel. If you need something more economical, That Front wheel drive is the best option., which has the perfect combination of features. well and rear drive it is worth choosing only if you have experience and you need a car, first of all, in order to enjoy driving.
Front wheel drive benefits:
- Low price
- Reduced fuel consumption
- Cross-country ability is higher than rear-wheel drive
- Holds course well on slippery roads
Rear wheel drive advantages:
- Accelerates faster than the front
- Easier to get out of a skid
Advantages of all-wheel drive:
- Permeability is an order of magnitude higher
- Accelerates even faster than rear-wheel drive
Cons of all-wheel drive:
- High fuel consumption
- High price
- Expensive repairs and maintenance
We have analyzed the main types of drive, now let's see what are types of all-wheel drive.
Types of all-wheel drive
In this variant all four wheels are permanently connected to the engine, each of them always clings to the road and pushes the car forward and this in itself is a big plus (for example, on a slippery slope).
However, permanent four-wheel drive really good only when it is equipped with a stability control system ( ESP), which slows down the desired wheel and prevents it from slipping if it hits a more slippery surface.
disadvantage permanent all-wheel drive is high fuel consumption, and the advantage greater reliability. Concerning patency, then it is possible to storm off-road spaces on a permanent all-wheel drive, but only if its design provides for central and center differential locks.
Benefits of permanent all-wheel drive:
- Always ready
- High reliability
Disadvantages of permanent all-wheel drive:
- Increased fuel consumption
Manual all-wheel drive
This is the oldest and most inconvenient type of all-wheel drive, and here patency she probably has the tallest. Such a car, in normal condition, has rear drive, and the front wheels can be connected manually, but for this you need to make a stop. It is impossible to constantly drive with the front axle connected, it is impossible to drive such a car, as this creates a load on transfer case and accelerate tire wear. Also, the disadvantage of this scheme can be considered rather high flow fuel, regardless of whether all-wheel drive is on or off.
This type of all-wheel drive has its own advantages. First, such a drive is very good for off road, and secondly, it also has a very high reliability.
Advantages of manually connected all-wheel drive:
- High permeability
Cons of manually connected all-wheel drive:
- The inconvenience of turning on all-wheel drive
- High fuel consumption
This is the most modern look all-wheel drive And most promising, but it has not yet been perfected and does not handle serious off-road very well. Implementation Options automatically connected all-wheel drive are very different, but general principle such that one pair of wheels is connected to the engine permanently, and the second is connected only when necessary. This connection occurs through a multi-plate clutch, and the computer controls the whole process. Thus, normally the car has one axle drive, A becomes all-wheel drive only when it's really needed.
The main advantages of this scheme are fuel economy And Ease of use. The driver does not need to perform any action, the computer itself connects the second pair of wheels when necessary.
On the other side, multi-plate clutch much less reliable, how classic all-wheel drive. Automatic all-wheel drive allows you to ignore the snowdrifts in the city and easily climb the icy slope, but it is not intended for serious off-road assault.
Advantages of automatically connected all-wheel drive:
- Fuel economy
- Ease of use
Cons of automatically connected all-wheel drive:
- Lower Reliability
Now, friends, you know what's different different types drive and be able to do right choice. Be sure to rate the article, share it with your friends and leave your comments.
Front? Or maybe the back? Or maybe completely complete? Which of these types of drive is better and which one should be preferred? 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 in this article we will focus exclusively on the all-wheel drive of the car. In particular, about its advantages and disadvantages.
To begin with, it is worth understanding the terminology. All-wheel drive vehicles, as a rule, operate in 2 modes: AWD and 4WD. What is the difference? The first implies four-wheel drive, operating in constant or automatic modes. The second is all-wheel drive, manually connected and disconnected.
The purpose of the plug-in all-wheel drive is that the car's transmission can work in two ways. One provides a stable transmission of torque exclusively to one axle - usually the rear. Due to this, it increases maximum speed car and other characteristics. The other sends power to both axles at the same time, 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 you to evenly distribute power to all wheels, ensuring a comfortable ride without any resistance.
The center differential bears the brunt of the load, as it distributes the torque and at the same time transmits it to both the front and rear differentials.
Exclusively all-wheel drive systems do not include 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 all-wheel drive combines the advantages of other types of drive, driving a car equipped with it in real conditions is not so easy.
Especially with complex road conditions. After all, if rear wheel drive car in some situation, it requires a decrease in gas, and front-wheel drive, on the contrary, an increase, then all-wheel drive will require both. Everything will depend on the level of grip, 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 all-wheel drive can lose stability in an instant. Moreover, without giving the slightest prerequisites for this.
Another disadvantage of all-wheel drive is higher fuel consumption. This is explained by the all-wheel drive device itself. In addition, all-wheel drive systems are distinguished by the high cost of both maintenance and repair. Of course, the brand of the car and its model significantly affect the cost of maintenance. However, any all-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 cross-country ability. It is for her sake that such cars are bought.
Along with this, all-wheel drive vehicles have a pronounced dynamics that allows you to take off without wheel slip, regardless of the condition. pavement. But, as mentioned earlier, only one can fully experience all the advantages of 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. For the driver, his driving skills, the ability to control and analyze the situation, composure are of greater importance. These factors are the most important. And the drive ... Its role, for the most part, is optional.
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Scanner for self diagnosis car
At first glance, the principle of operation of the transmission of an all-wheel drive vehicle is simple: torque from power unit distributed between the four driving wheels. Such a machine is very convenient due to its pronounced advantages associated with unpretentiousness to the quality of the coating under the wheels. On a primer, in ice, on a wet countryside or on a highway in a heavy downpour, an all-wheel drive car will show itself at its best. Plus, on it you can not be afraid to move off the asphalt and cross the terrain without even a hint of the road, and on the pavement all-wheel drive makes itself felt good start and acceleration, with virtually no slippage.
But sometimes there are incidents that, it would seem, are difficult to explain due to the advantages that all-wheel drive vehicles have. It happens that the driver sits behind the wheel of an SUV with an impressive ground clearance, and the car got stuck in the "porridge" and lay on its belly.
Interesting to know! In 1883, the American farmer Emmett Bandelier patented a design similar to the current all-wheel drive system.
Of course, there can be many reasons for this, the most common of which, as experienced drivers jokingly say, is “gasket between the steering wheel and the seat.” But it also happens that the transmission of the "all-terrain vehicle" does not intend to cope with the tests. And then reasonable questions arise: “Why can’t it cope?”, “Which one can handle it?”. We will talk about this further in the material provided.
Manual all-wheel drive (Part-Time)
This type of transmission can rightly be called the "first-born" among all-wheel drive. The principle of its operation is the rigid connection of the front axle. Thus, all wheels rotate at the same speed, and the center differential is not provided. Torque is distributed equally between all wheels. Nothing to do in this case, so that the axles rotate at different speeds, will not work, except to infiltrate the “womb” of the car and mount a new differential.
In the meantime, it is not recommended to dissect in a car stream with a connected front axle. If you move even in low gear straight for short distances, nothing bad will happen, but if you need to turn around, then the resulting difference in the length of the bridges becomes an obstacle. Since the distribution is 50/50% between the axles, the excess power comes out only by slipping the wheels of one of the axles.
On sand, gravel or mud, the wheels can slip if necessary, and nothing will interfere with them, since grip is weak. But if the weather is dry, and you are driving on an asphalt road, then there will be nowhere for the power to go, like off-road. Thus, the transmission is subjected to increased loads, the rubber wears out faster, controllability deteriorates and directional stability is lost at high speeds.
If the car is used more often off-road or generally purchased only for cross-country rides, then the all-wheel drive system with the forced connection of the front axle will fully meet your expectations. The bridge is connected immediately and hard, so you don’t have to block anything. The design is very simple and reliable, there are no locks and differentials, there are no drives of either electrical or mechanical type, there is no excessive hydraulics and pneumatics.
But if you're an urban dandy, value your time, and don't want to worry about the weather and the alternating sections of the city with its loose and slippery road surfaces and treacherous deep puddles, then this all-wheel-drive system option is absolutely not for you. If you move around with the front axle always forcibly connected, then this is fraught with wear and subsequent damage, it is not very convenient to constantly manipulate it, and in general you may not have time to connect it.
Cars with Part-Time: Suzuki Vitara, Toyota Land cruiser 70, Great wall hover, Nissan Patrol, ford ranger, Nissan Navara, Suzuki Jimni, Mazda BT-50, Nissan NP300, Jeep Wrangler, UAZ.
Permanent four-wheel drive (Full-Time)
The disadvantages of plug-in all-wheel drive led to the creation of a newer invention - permanent all-wheel drive, which is devoid of all the problems that Part-Time had. This is the same uncompromising “4WD”, which is devoid of any “ifs” there: all the wheels are driving, there is a free differential between the axles, which releases the accumulated excess power due to the scrolling of one of the gear satellites, which contributes to the movement of the car with permanent all-wheel drive. The main nuance of cars with this type of all-wheel drive is slipping. If the car begins to slip on one axle, the second one is automatically turned off.
Now the car has turned into furniture or a house, as you wish, in general, into real estate. How does it happen? If one wheel starts to slip, the inter-wheel differential disables the second, and the second axle is also automatically disabled by the differential, but already the inter-axle one. Of course, in reality, the stop does not happen so quickly. Movement is a dynamic process, therefore, there is a power reserve, an inertial force. The wheel turns off, moves by inertia a couple of meters and turns on again.
But in this case, the car will stall somewhere sooner or later. Therefore, in order to preserve all the off-road qualities of the “rogue”, one or two forced locks of the center differential are usually installed on such cars. It is very rare to find a factory lock in the front differential. If desired, it is installed separately.
But the permanent all-wheel drive system is also far from ideal driving performance on paved roads. Such cars rulitsya, let's say, I would like it better. In critical situations, the SUV pulls out of the turn and it does not immediately respond to steering and gassing. Drivers of such vehicles require special skills and excellent vehicle feel.
To improve handling, they began to install interaxle self-locking differentials with a forced locking system. Different automakers used different solutions: some Torsen-type differentials, some viscous couplings, but the task for all is the same - to improve the car's handling, and this requires a partial differential lock.
If one of the axles begins to slip, the self-locking mechanism is activated, and the differential does not affect the second axle, to which the torque continues to flow. A number of cars were also equipped with a self-locking rear axle differential mechanism, which had a positive effect on the sharpness of control.
Among cars with permanent all-wheel drive, one can distinguish Toyota Land Cruiser 100, 105, Land Cruiser Prado, Land Rover Discovery, Land Rover Defender, Lada 4x4.
Torque on-demand automatic all-wheel drive (AWD)
Time and the inquisitive minds of automotive engineers have done their job, developing the all-wheel drive system into something new with the introduction of electronically controlled systems with the redistribution and transfer of torque. As a result, stabilization and exchange rate stability systems appeared, traction control systems, as well as systems that distribute torque. All of them are implemented using the involved electronics. The more expensive the cost of the car and the more modern its filling, the more complex schemes are applied to it.
This is tracking the steering angle, body roll and speed, up to how often the wheels oscillate over a certain distance. The car carries out the most complete collection of information about its behavior while driving. The ECU processes it and regulates the transmission of torque between the axles through an electronically controlled clutch that has replaced the differential. On modern sports cars this invention has become very worthy of attention.
To date, electronic systems can be called almost ideal in their behavior. It only takes manufacturers to add a few new sensors and parameters that make the system proactive.
But even here there are some nuances of use: this type of all-wheel drive transmission is suitable for operation only on asphalt roads with occasional interspersed with symbolic off-road, primer, for example. Basically, electronic clutches, when slipping off-road, begin to get very hot and fail. And for this you do not need to plow tank tracks for hours, ten minutes of skidding on ice is enough. And if it is systematically overheated, then damage cannot be avoided, as well as costly repairs.
The "cooler" the system, the more prone it is to breakdowns. So you need to choose a car wisely, having determined for yourself which tracks you will ride it on. Do not go to extremes: if an SUV, then only in the forest and in the village, and if a passenger car, then only in the city. There are plenty of cars from this segment that are versatile in their driving characteristics. But also without fanaticism, too. On passenger car you can, of course, go to a country road, but which one and which one is another question.
If the wiring breaks on one of the ABS sensors, the entire system will fail at once and will not receive information from the outside. Or filled with gasoline best quality- and that's it, the downshift does not turn on, there is a trip to the car service ahead. Or it may happen that the electronics will put the car into service mode, completely turning off all the systems of its life.
Among these vehicles, it is worth highlighting Kia Sportage (after 2004), Cadillac Escalade, Nissan Murano, Nissan X-Trail, Ford Explorer, Toyota RAV4 (after 2006), Land Rover Freelander, Mitsubishi Outlander XL.
Multimode (Selectable 4wd)
This system is perhaps the most multifunctional in relation to the all-wheel drive with its various manipulations: it can be activated manually or automatically, as well as forcibly disabling the rear or front axle s. Using the Selectable 4wd system does not increase fuel consumption. The leaders in fuel overruns are the cars with part-time mentioned at the beginning.
Some cars with a selective transmission, which can be called permanent all-wheel drive, with the ability to forcibly turn off the front axle, stand apart. On such vehicles, the transmission combines part-time and full-time. Among them Mitsubishi Pajero, Nissan Pathfinder, Jeep Grand Cherokee.
In Padzherik, for example, you can choose one of several transmission modes: 2WD, 4WD with automatic center differential lock, 4WD with hard differential lock, or downshift. As you can see, here you can find references to all the above all-wheel drive systems.
Some front-wheel drive cars may have a driven rear axle. A small electric motor is mounted in the final drive housing, which is connected at the request of the driver - the e-4WD system. The electric motor is powered by car generator. Such a system improves the controllability of the car on the track in a downpour, and also helps to confidently pass snowy, icy and muddy sections of the road. A prominent representative of cars with this system is latest models bmw.