Almost every motorist has an idea about the types of car drives, or, in extreme cases, knows what type of drive drives his vehicle. Let's try in this article to figure out what drives still exist and what is their significant difference. So, in order for the car to be set in motion, the torque from the engine must be transmitted to the wheels of the car. But how many wheels will take torque, and on which axle, depends on the type of drive.
Drives can be of three types: rear, front and full. Let us consider in more detail their difference, as well as the pros and cons of operating a car with different types of drives.
Rear drive
If the car is equipped with rear-wheel drive, all the energy of the engine will be completely transferred to the rear axle. You can meet this type on domestic "classics", as well as Japanese, European and American high-class cars. There are, of course, indisputable advantages of this option - dynamics, starting from a place, lack of vibration, which to some extent increases the comfort of operating the car. The disadvantages include an excessive tendency to skid, especially on slippery road surfaces. Permeability, compared with front-wheel drive, is slightly lower.
Front drive
Cars equipped with front-wheel drive, all the energy of the motor, respectively, is taken to the front axle. This type of drive is found more often on budget modern cars, but can also be found on more expensive models. FWD vehicles are less prone to skidding on slippery roads and cornering than RWD vehicles, and also have comparatively better off-road capability. The advantages of this type of drive are practicality, adequate price and ease of operation. It will be easier for novice drivers to get used to driving in front-wheel drive.
Finally, all-wheel drive vehicles. Unlike the options discussed above, the all-wheel drive system is the distribution of engine torque to the front and rear axles, namely to all four wheels. The distribution can be carried out in different ways, so the all-wheel drive system is divided into subtypes:
- The energy of the motor can be distributed unevenly between the wheels, depending on the traffic situation and the condition of the roadway.
- All engine energy is supplied to the main drive axle (it can be front or rear, depending on the car model), but in the event of slipping of the main drive wheels, part of the energy is redistributed to the second axle, putting it into operation as well.
- And, of course, even distribution of energy between all wheels.
Watch the video tutorial about the types of car drives - their advantages and disadvantages:
As we found out, all types of drives have their advantages and disadvantages. With which drive to choose a car - it's up to you.
Drive types.
Almost every car enthusiast knows what kind of drive a car has, or at least knows what kind of drive is on his car. Let's see what types of drive still exist and what are their differences. So, in order for the car to go, it is necessary that the torque from the car engine is transmitted to its wheels. Depending on how many wheels this torque will take, the type of drive also depends.
There are three types of drive: front, rear and all-wheel drive.
Front wheel drive car.
Front-wheel drive vehicles get all of the engine's power to the front wheels. At a minimum, this is logical, because on most cars the engine is in the front and the front end is more loaded, and therefore has more grip on the front wheels. More often, such a drive is found on modern budget-class cars, but it also happens on expensive models. A front-wheel drive car is prone to skidding in corners on uneven surfaces, but to a much lesser extent than rear-wheel drive cars. But still, cars with front-wheel drive are much more often endowed with another drawback - understeer, that is, the demolition of the front drive wheels to the outer radius when cornering. And if this “ailment” in most regular situations does not make itself felt, then with active driving it can cause a lot of trouble to the driver. In the event of understeer, the dynamic stabilization system we have considered can come into play and eliminate a potentially dangerous situation. In addition, with an active start, the front of the car is unloaded, as a result of which it no longer has the maximum level of grip. For this reason, it is difficult for front-wheel drive vehicles to realize the full potential of the engine during acceleration if its power exceeds 200 hp. For better behavior of the car on the road under this condition, it is equipped with an Anti-Slip System or a cross-axle differential lock to avoid slipping of the drive wheels.
Advantages front drive:
Flaws front drive type:
- Vibration from the motor due to the rigid mounting is transmitted to the body.
- The steering wheel during intensive acceleration transmits reactive forces (expressed in the form of shocks). Therefore, front-wheel drive vehicles with a capacity of more than 250 hp. as a rule, they are not released due to the inability to realize the potential of the engine.
- With a sharp start, the weight is redistributed back, the front axle is unloaded, and the drive wheels tend to slip.
- Demolition of the front of the car.
Rear wheel drive car.
With rear-wheel drive, the entire power of the engine goes to the rear wheels. The positive side of this drive is excellent handling and dynamics, the absence of vibration (transmitted to the body and steering wheel) has a positive effect on comfort for both the driver and passengers. Therefore, in modern cars, rear-wheel drive is used on premium brand models or on sports models in which gambling handling and a “clean steering wheel” are important, to which vibrations that worsen the “feeling of the car” will not be transmitted. One of the main disadvantages of rear-wheel drive is the tendency to skid, especially on slippery roads. This effect is manifested in the fact that with an excess of traction on the drive wheels, the rear of the car begins to skid - this is called skidding or excessive oversteer.
Rear wheel drive advantages:
The steering wheel is not affected by reactive moments during acceleration, which improves the quality of control over the car.
When accelerating quickly and sharply from a standstill, the weight of the machine is redistributed to the rear and the drive wheels are less prone to slip and loss of traction, which allows you to start more efficiently.
The axle load is well distributed, work is optimally distributed between the front and rear tires, which prevents their rapid wear.
Disadvantages of rear wheel drive:
The high cost of production, which is reflected in the final price of the car.
Rear wheel drive vehicles are heavier than front wheel drive vehicles. They, as a rule, always have a tunnel in the center of the body, which “eats up” the useful volume of the cabin and reduces the comfort of the rear passengers.
Traction in snow and mud conditions is worse than that of front- or all-wheel drive vehicles.
Tendency to skid the rear axle of the car.
All-wheel drive vehicle.
When the energy of the engine is transmitted to all four wheels of the car, such a drive is called all-wheel drive. In bad weather or difficult road conditions, motorists often have thoughts about purchasing a car with all-wheel drive or, in other words, an all-wheel drive car. When mentioning this type of car, off-road vehicles often come to mind, but in modern conditions this is most likely an established stereotype: all-wheel drive transmission today is by no means the prerogative of “jeeps”, but a completely traditional common scheme, albeit with many variations in execution, but found even in small cars. The advantages of all-wheel drive cars include good cross-country ability and the ability to start from a standstill without wheel slip on almost any road surface. The main disadvantage of all-wheel drive is that it is heavy and expensive. At some points, the behavior of an all-wheel drive car on the road can become unpredictable. This can happen due to uneven distribution of torque to the wheels (for example, one wheel loses traction with the main road surface). This type of drive requires careful driving.
Regardless of which drive the future owner chooses a modern car, it will be equipped with one or another dynamic stabilization system that will make your trip as comfortable and safe as possible under unpredictable road conditions. Before considering in more detail the various options for all-wheel drive, it is necessary to define such a device as a differential and the reasons for its need in the design of any type of drive circuit for cars.
A differential is a gear device that transmits torque to the drive wheels and provides them with different rotation speeds to ensure the vehicle turns without tire wear (the inner wheel has a shorter path than the outer one).The differential is one of the main structural elements of the transmission.
The location of the differential in the transmission of the car:
In a rear-wheel drive vehicle, to drive the drive wheels - in the rear axle housing;
In a front-wheel drive car to drive the drive wheels - in the gearbox;
In an all-wheel drive vehicle to drive the drive wheels - in the crankcase of the front and rear axles;
In an all-wheel drive vehicle to drive the drive axles - in the transfer case.
The differentials used to drive the drive wheels are called cross-axle. The center differential is installed between the drive axles of an all-wheel drive vehicle.
The presence of differentials is a major stumbling block in all-wheel drive technology, as it has a huge impact on how a car behaves on the road. If we consider the simplest example of AWD with three "free" differentials, it becomes clear that the car can be immobilized if at least one of the four wheels loses traction. A feature of a simple "free" differential is that it redistributes power in favor of an axle that has less resistance.
Thus, if one wheel loses traction, all the developed power is transferred to it. At the same time, an all-wheel drive car is twice as likely to lose the grip of one drive wheel with the road than a car with a drive to one axle. And since the use of an all-wheel drive vehicle involves more frequent driving in poor road conditions, it becomes very important for him to have any kind of differential lock: center, center or all together.
Automakers have implemented a fairly large number of layout schemes and formulas, so let's try to clarify some points. In turn, all-wheel drive can be divided into subtypes.
Plug-in all-wheel drive(Part Time)
Part-time 4WD, (eng. "Part time" - part of the time) - four-wheel drive for temporary use. When driving on paved roads, all traction is transmitted to only one axle, usually the rear axle. The second bridge is connected by the driver using a lever or button.
Vehicles with plug-in all-wheel drive do not have a center differential that would allow the driveshafts to rotate at different speeds when the car turns. With all-wheel drive on, the front and rear driveshafts are rigidly connected to each other through the transfer case and rotate at the same speed. In a turn, the front wheels of the car travel a longer distance than the rear wheels, which causes stress in the transmission, increased tire wear, and so on. These effects can only be mitigated by wheel slippage. Therefore, the use of such a four-wheel drive is limited to areas with a very low coefficient of adhesion (mud, snow, ice, sand). On a dry paved road, it is not recommended to connect this type of all-wheel drive, in order to avoid serious damage.
Auto-connected all-wheel drive(TOD - Torque On Demand - torque on demand).
In such an all-wheel drive system, under normal road conditions, only one axle is leading. All-wheel drive is connected if necessary. As a rule, this happens when the wheels slip and, as soon as the slip is eliminated, the four-wheel drive is turned off. To connect the second axle, a viscous coupling can be used, or a multi-plate clutch driven by a hydraulic pump, self-locking when there is a difference in the speeds of rotation of the front and rear axles; or an electronically controlled multi-plate clutch that receives information about the slip from the ABS sensors and captures the slightest difference in the speeds of rotation of the front and rear axles.
Many car owners still do not understand what the encrypted types of drives mean, which is not surprising, because these are English abbreviations. Therefore, we will immediately clarify the situation: RWD - Rear Wheel Drive - rear-wheel drive; FWD - Front Wheel Drive - front-wheel drive; 4WD - 4 Wheel Drive - 4-wheel drive ("4x4"); AWD - All (in some sources Automatic) Wheel Drive - automatic all-wheel drive. Thus, the penultimate and last positions are characterized by all-wheel drive, but with their own individual characteristics.
Experience shows that you should not be guided by such criteria as, for example, fuel consumption or car weight when it comes to the level of traffic safety. Although even the “coolest” jeep is not immune from loss of control, when purchasing equipment, decide why you need it and measure your abilities with the style of future driving.
If, after studying the technical specifications, you continue to doubt, do not hesitate to seek advice from specialists and, just in case, ask them in detail about the AWD drive: what kind of transmission option is this?
Types of car drives
Let's take a closer look at each type of drive, as well as analyze the advantages and disadvantages.
RWD
The use of such a drive creates the following advantages:
- Easy turning due to small radius. It is achieved due to the fact that the front wheels are not limited to a complex drive axle system.
- Even in the case of a rear independent suspension, the car does not need to install constant velocity joints.
- Controlled drift, which can be quickly localized by turning the steering wheel in its direction and adjusting the speed.
- Lightweight steering due to the absence of jet moments.
- Good acceleration dynamics and confident climbing.
- Appreciated by scorchers, lovers of fast and furious.
- Optimal weight balance.
When driving, the weight of the vehicle with RWD is transferred to the rear wheels, as a result of which the car gets better grip on the road, and acceleration dynamics improves
Alas, along with the advantages, there are also disadvantages. There are fewer of them, but they are incommensurably more significant:
- Lack of control on a problematic road. This is especially felt in icy conditions and on damp soil. To optimize control, it will be necessary to install more advanced stabilization and clutch control systems. Partially improve this problem can expensive profile rubber.
- RWD vehicles tend to cost several times more than their front wheel drive counterparts. This paradox is due to the complicated transmission device and costly chassis parts. This key circumstance must be taken into account when choosing a purchase.
- Tendency to slip. The front wheels cause increased resistance when cornering, which the rear-wheel drive cannot cope with; the result is a slippage that provokes a skid.
- Burnout of fuel. A rare representative of the RWD family can boast that it "eats" less than 10 liters per 100 kilometers, even on the highway.
- The drive circuit is quite cumbersome and generates certain losses in traction and power.
Representatives: BMW 3-Series E30, Cadillac CTS, Chevrolet SS and Camaro, Dodge Challenger, Charger and Magnum, Chrysler 300, Ford Mustang and Sierra, Hyundai Genesis, Jaguar S-Type, Lexus GS, Mazda MX-5, Mercedes E -Class W124, Nissan 370Z, Opel Omega, Scion FR-S, Smart Fortwo, Subaru BRZ, VAZ-2106.
FWD
Front-wheel drive is initially characterized by resistance to understeer: when turning the wheels, due to their own traction, they tend to return to their original position. This property is considered a sign of car safety and a favorable condition for an average driver.
An FWD vehicle weighs 3-5% less than a RWD vehicle.
A car with this type of drive is the most common in the global automotive industry. For some time now, it has occupied the niche of the most economical and relatively inexpensive passenger vehicles. Calculated: its cost, weight and "appetite" is much less than the rear-wheel drive. On the conveyor, it is easier to assemble the “motor + front-wheel drive” assembly and simply insert it under the hood, while the rear axle requires a technological tunnel in the car floor and much more. Therefore, only front-wheel drive is installed on mid-size “passenger cars” (especially mini-jeeps and SUVs). This option is ideal for those who prefer to travel around settlements, sometimes leaving them. However, even outside the city, driving is usually carried out on a flat road surface with little damage. With such an uncomplicated mission, front-wheel drive vehicles cope without much difficulty.
- Compactness.
- Relatively high permeability.
- Best steering efficiency.
- Insufficient maneuverability.
- Frequent slipping of the front wheels during a sharp start.
- Rigid fastening of the engine, as a result - a noticeable vibration.
- Power limitation (a power unit over 200 hp wears out the chassis and impairs handling).
It is important! The interpretation of "F" in the abbreviation FWD as Full ("full") or Four ("four") is erroneous, absolutely incorrect and confuses the classification.
Representatives: Audi A4, AZLK-2141, Chevrolet Impala, LuAZ-969В, VAZ-2108, Mitsubishi Lancer, VW Golf.
4WD
Permanent four-wheel drive involves a stationary connection of all wheels through a multi-stage transmission system with a motor. That's what the center differential is for. So, the VAZ-2121 is equipped with its forced blocking, which puts the Niva on a par with off-road vehicles with all-wheel drive.
With the “4x4” format, you can adjust the distribution of rotation between the wheels - some models have the ability to turn off the torque to the front axle (UAZ, Mitsubishi Pajero). However, it must be taken into account that in recent years, all-wheel drive with the on-off function has been produced extremely rarely by manufacturers, because this option has proven to be inefficient and expensive.
In many cars with 4WD drive, an independent choice of distribution of power between four wheels is provided.
I must say that the transfer case is gradually becoming a rarity. The mechanics are replaced by cybernetics, which autonomously monitors the process of rotation of the ramps and maintains the optimal mode of operation of the transmission. Be that as it may, traditional schemes, when the driver can optionally turn on a reduced traction gear at low speed and increased crankshaft speed, are still found. This is a very good help in a critical situation, for example, if the vehicle is stuck in the snow or plowing.
It is convenient when, if necessary, it is possible to turn on 2H - a transmission on one axle, acting as a classic rear-wheel drive. If this is not enough, switch to 4H and smoothly overcome obstacles. However, the main feature that distinguishes 4WD from other drives is a special technological mode - 4L (low gear). With it, 4 wheels are completely blocked and rotate at the same frequency. For the city, the mentioned mode is useless, but for a deep snowdrift or bog - just right! Pure engine power, applied in equal parts to both axles, will pull out of the viscous and loose mass without slipping.
Representatives: Audi Q3-SQ7, Bentley Bentayga, BMW X1-X6, Chery Tiggo, Daewoo Winstorm, Dodge Journey, Fiat Fullback, Jaguar F-Pace, Jeep Wrangler, Toyota Land Cruiser, Land Rover.
AWD
This know-how has found application mainly in crossovers. Its principle is that the drive shaft rotates the front axle and only when there is not enough traction, the electronics gives the command to start the rear axle. Thrust distribution is roughly 60% front and 40% rear. But there are exceptions: on Audi and Subaru, the effort is divided in half.
AWD produces less torque than 4WD. In addition, AWD does not have the ability to turn on a low torque transmission (there is no demultiplier-divider here).
Automatic all-wheel drive is most often used in modern crossovers.
However, if we are talking about AWD and 4WD, then we understand that nominally mechanical rotational energy is distributed here and there over all 4 slopes. In fairness, it is worth noting: in some parts of the world, these two designations are generally identical. They neglect the fact that the AWD is equipped with a special operating unit located in the middle of the car. He distributes power to both bridges at his own discretion, that is, as he sees fit. Such functional selectivity optimizes the acceleration process, strives for an economical driving style, but when driving on ice or mud, involuntary drifts can be observed. In general, you should get used to the work of AWD, you need to learn how to feel it and predict the phases of activity, but this takes time and patience.
This is not to say that the AWD transmission is safer when driving in the winter. In this regard, experts warn: by and large, four-wheel drive has no advantages in braking or on snowy, icy turns. It only helps in some moments to maintain stability and creates the illusion of security.
Let's say you are driving calmly on a wet, slippery surface. Obviously, in such road conditions, the car is front-wheel drive. But here the car enters a problematic turn. At this moment, the transmission reacts to a change in the situation, and the car goes into an unintentional skid. In turn, the driver in this situation also needs to have time to react to this sudden “surprise”, otherwise the accident cannot be avoided.
Representatives: Volvo S60, VW Golf III-IV, Subaru Impreza.
The difference between 4WD and AWD
Generally speaking, AWD provides automatically connected four-wheel drive, and in 4WD it is either permanent or manually connected and disconnected. By the way, in auto topics, the not yet fully established terminology is sometimes violated, which confuses the consumer even more. For example, Ford Tempo and Subaru Justy at one time were “promoted” on the market as cars equipped with AWD, although in fact the operation of the drive axles was adjusted manually. But in world practice there is also such a thing as on “demand four wheel drive”, that is, a 4-wheel drive that can be connected if necessary. From it it is not clear who controls this system - a person or robotics. One way or another, mostly irresponsible media are to blame for such a “vinaigrette”, allowing lapses in the publication of auto reviews, price lists and press releases, as well as Internet copywriters, voluntarily distorting information in pursuit of uniqueness.
Part-Time 4WD came first and is the simplest and most reliable type of all-wheel drive.
Previously, the overwhelming majority of cars were single-wheel drive, with a rear (less often front) driving pair. Then samples were created with a transfer case ("razdatka"). Through it, the thrust was distributed between the axles in the proportion established by the designers. So the first all-terrain vehicles appeared. Later, a number of versions of the all-wheel drive version of the transmission were invented:
- Part-Time 4WD - partial four-wheel drive. Only short-term use of a system of this type is allowed, because on dry hard roads its increased wear and failure is observed.
- Full-Time 4WD is a total non-switchable drive. Torque is continuously distributed between the axles in a ratio that has a constant value. The car in this drive mode moves over arbitrary terrain, however, to achieve truly off-road qualities, it is equipped with a rigid locking of the center and wheel differentials.
- AWD - all-wheel drive, working in automatic mode. A computer or a viscose clutch determines the moment of wheel slippage on their own, additionally connecting the second axle.
Which one is better in different situations
AWD or 4WD, FWD or RWD? Due to the fact that many are lost, the car with which particular transmission system to purchase, the controversy among motorists does not subside, which type of drive is most relevant today. Analysts also broke a lot of copies on this issue ... Let's look into this problem.
In the first place when choosing a product is the factor of correlation of cost with the financial potential of the buyer. On the second - his taste preferences. On the third - features of the place of residence and lifestyle.
If we are talking about frequent off-road driving, it is recommended to choose cars with 4WD drive, but in the city FWD is enough
For southerners, 4WD and AWD are, in principle, not relevant, especially when you consider that they cost more and consume more fuel. It is enough for them to purchase a front-wheel drive, or even a rear-wheel drive vehicle with high-quality winter tires. In any case, it will be rational, in a businesslike way.
In the middle lane with moderate winters, FWD is best. Its advantage in the cold season is that the largest mass of the car is concentrated on the front axle (gearbox, engine, suspension). Thanks to this, the driven front ramps have optimal traction, in contrast to the rear-wheel drive.
| Factors | |||
| car cost | Medium | Minimum | High |
| Handling on dry roads | Excellent | Excellent | Excellent |
| Handling on slippery roads | Satisfactory | Good | Excellent |
| Cross-country ability (snow/mud) | Satisfactory | Satisfactory | Excellent |
| Dynamics | Good | Satisfactory | Excellent |
| Design complexity/total weight | Medium | Minimum | High |
| Braking efficiency | Excellent | Satisfactory | Excellent |
| Maneuverability | Excellent | Satisfactory | Satisfactory |
| Fuel consumption | Average | Minimum | High |
For mountainous, sandy terrain, swamps, snowdrifts, 4WD is definitely required. AWD is also designed to overcome off-road, but more passable. On a steep slope and in impassable mud, it is not suitable - it will not pull. In addition, cars equipped with AWD have slightly less ground clearance than full-fledged all-wheel drive, which are considered 4WD. Therefore, you should not tempt fate on AWD and drive along rocky paths or forest bumps and ditches.
AWD is an advanced, smart system of the 21st century. Moderately capricious, because it is in the process of improvement. However, for the urban cycle, as well as for a mild winter of the Scandinavian type, this is an unmistakable solution. In addition, AWD consumes significantly less fuel compared to 4WD.
As for RWD, current experts note its impracticality and inconvenience in almost all aspects.
Rear-wheel drive was provided on the so-called "classic" VAZ cars
Basically, the population becomes the owner of the vehicle in order to drive it to work and home. The most balanced option for this purpose is a front-wheel drive small car. The fact is that the front-wheel drive significantly saves fuel in comparison with the more weighty all-wheel drive version.
Currently, there is a tendency to gradually abandon RWD, which is not surprising, because this is the trend of the last century. To date, it has mainly remained on fireballs and powerful sedans. And in the latter case, this is a tribute to tradition and a new fashion, and not a necessity, because only with rear-wheel drive is a full-fledged drift possible. Rear-wheel-drive super-SUVs (notably the 4 Runner and Tahoe) are also more of an exception to the rule in order to maximize the model's capabilities. Other rear-wheel drive vehicles (such as pickup trucks) are designed to transport goods. And the bulk of all-terrain vehicles are equipped with a 4x4 drive for maximum power and torque. AWD in a certain sense acts here as a universal development.
Every motorist knows, or at least heard about the different types of car drives. But if there are still those who have not heard about it, then we will try to figure it out. The fact is that the torque from the engine is transmitted to the wheels (this is necessary for the car to drive), and so, depending on how many wheels this torque will take, the type of drive also depends. There are three types of drive: full, rear and front. Let's talk in more detail about each of them and find out why they are good and what their disadvantages are.
Types of car drives
If the energy of the engine is transmitted to all four wheels, such a drive will be called full. He, in turn, is also different. It happens that the distribution of energy between the rear and front axles is uneven. For example, in a Lamborghini Gallardo, 70% of the energy comes from the rear axle and only 30% from the front. It is also possible to receive energy only by the front wheels, but in the event of a slip, the rear ones are also included in the work. One of the representatives of such a car is Mitsubishi Outlander. There is also a distribution of energy in absolutely equal shares.
The advantages of all-wheel drive cars are excellent cross-country ability and the ability to start from a standstill without wheel slip on almost any surface. Cons - a rather heavy and expensive type of drive. And most importantly, at some points the behavior of the car on the road can become unpredictable. This can happen due to uneven distribution of torque to the wheels, which is possible in a situation where, for example, one wheel loses traction. Therefore, we can say that this type of drive requires careful driving and serpentine racing by a non-professional racer is contraindicated (however, as well as on any other drive :)).
With rear-wheel drive, as you might guess, the entire power of the engine goes to the rear wheels. This type is typical for American cars. Such a drive is also found on high-end European and Japanese cars. The advantages of this drive include excellent dynamics and controllability. The absence of vibration transmitted to the body and steering wheel has a positive effect on comfort for both the driver and passengers. Of the minuses, it should be noted the tendency to skid when starting on a slippery road.
Front wheel drive vehicles get all of the power from the engine to the front wheels. The majority of modern budget cars are the owner of this, and expensive models come across. The absence of a cardan creates less weight, but the front of the car is still heavier than the rear, as a result of which the car is prone to skidding in corners on uneven surfaces, although to a much lesser extent than rear-wheel drive cars. The advantages include ease of use, low cost and practicality. Learning to drive a front-wheel drive car is easier than rear-wheel drive and all-wheel drive, which is good for novice drivers.
Which drive do you prefer?
BUT! All this discussion about the drive today, by and large, is meaningless, since most modern cars are equipped with many stabilization systems, and if you sit behind the wheel of a rear-wheel drive BMW, you can immediately feel how pleasant it is to drive and how predictably it behaves in difficult road conditions. conditions, unlike the VAZ Kalina with front-wheel drive, for example.
Therefore, answering the question which drive is better, we have to state that there is no best drive. You need to learn how to drive a car well and feel its behavior on the road. Be attentive while driving and respond in time to changes in the road surface and the traffic situation in general.
Many lovers of outdoor activities and frequent trips out of town choose crossovers and SUVs, which use all-wheel drive, as a vehicle. Such cars are distinguished by increased ground clearance and all-wheel drive, which provides good cross-country ability.
But not always such cars are able to overcome even average off-road, not to mention serious dirt. And the reason for this may be the same all-wheel drive, or rather its design features. Therefore, the presence of all driving wheels does not mean that the machine is capable of conquering strong mud.
The main components of the transmission
Four-wheel drive means the transmission of torque from the power unit to the wheels of both axles, which increases the mud throughput.
The main design feature of this type of drive over others (front, rear) is the presence of an additional unit in the transmission - a transfer case. It is this node that ensures the distribution of rotation along the two axes of the car, making all wheels drive.
In general, this auto transmission consists of:
- clutch;
- gearboxes;
- transfer box;
- drive shafts;
- main gear of both bridges;
- differentials.
All-wheel drive transmission design option (automatically connected)
Despite the use of the same components, variations and designs of transmission - a lot.
Design and operational features
It is worth noting that on many cars all-wheel drive is not always carried out. That is, only one axis is always leading, while the second one is connected only when necessary, and this can be done both automatically and manually. But there are also variations of the transmission, in which the axle is not disabled.
Transmissions with a design that provides rotation to all wheels are used on cars with both a transverse installation of the power unit and a longitudinal one. In this case, the layout predetermines which of the leading axles functions constantly (the exception is permanent all-wheel drive).
The system that provides all-wheel drive can work with both manual transmission and any automatic transmission.
The principle of operation of the system is quite simple: from the motor, rotation is transmitted to the gearbox, which provides a change in gear ratios. From the gearbox, the rotation enters the transfer case, which redistributes it to two axles. And then, through the cardan shafts, the rotation is transmitted to the main gears.
But the general concept of the all-wheel drive system is described above. Structurally, the transmission may differ. So, as a rule, on a car with a transverse arrangement, the main gear of the front axle and the transfer case simultaneously enter into the design of the checkpoint.
But in a car with an engine installed longitudinally, the transfer case and the main gear of the front axle are separate elements, and the rotation on them comes from the drive shafts.
There are a number of design features that directly affect the patency of the car. First of all, this concerns the transfer case. In full-fledged SUVs, this node necessarily has a reduction gear, which is far from always available in crossovers.
Differentials also affect off-road performance. Their number may be different. Some cars have a center differential included in the transfer device. Thanks to this element, it is possible to change the ratio of the distribution of torque between the axles, depending on the driving conditions. In some cars, to increase cross-country ability, this differential is also blocked, after which the distribution of rotation over the bridges is done in strictly specified proportions (60/40 or 50/50).
But there may not be an interaxle differential in the design of the system. But cross-axle differentials installed on the main gears are present on all cars, but not all have their locks. This also affects driving performance.
The drive mechanisms are also different. In some cars, everything is done automatically, in others, the driver uses electronic systems for this, in others, the connection is completely manual, mechanical.
In general, the all-wheel drive system used on a car is not as simple as it initially seems, although the principle of its operation on all cars is the same.
The most famous systems are:
- 4Matic by Mercedes;
- Quattro from Audi;
- xDrive from BMW;
- 4motion of the Volkswagen Group;
- ATTESA at Nissan;
- Honda's VTM-4;
- All wheel control developed by Mitsubishi.
Types of drive used on cars
Three types of all-wheel drive have been used on cars, differing from each other both structurally and in terms of operation features:
- Permanent four-wheel drive
- With auto bridge
- With manual connection
These are the main and most common options.
Types of all-wheel drive
permanent drive
Permanent four-wheel drive (international designation - " full time”), perhaps the only system that is used not only on crossovers and SUVs, but also on station wagons, sedans and hatchbacks. It is used on cars with both types of power plant layout.
The peculiarity of this type of transmission is that the mechanism for disabling one of the axles is not provided. In this case, the transfer case can have a downshift, the inclusion of which is forced by an electronic drive (the driver simply selects the desired mode with the selector, and the servo switches).
Selector for selecting low gear and traffic intensity depending on the terrain
Its design uses a center differential with a locking mechanism. In different types of transmission, blocking can be carried out by a viscous clutch, a friction-type multi-plate clutch, or a Torsen differential. Some of them perform blocking in automatic mode, others - forcibly, manually (using an electronic drive).
Cross-axle differentials in the permanent all-wheel drive system are also equipped with locks, but not always (usually not on sedans, station wagons and hatchbacks). Also, it is not necessary to have a lock on two axles at once, often such a mechanism is installed on only one of the axles.
Drive with automatically connected axle
In a car with an automatically connected bridge (designation - " On Demand”), all-wheel drive is activated only under certain conditions - when the wheels of a constantly working axle began to slip. The rest of the time, the car is front-wheel drive (with a transverse layout) or rear-wheel drive (if the engine is located longitudinally).
Such a system has its own design features. So, the transfer case has a simplified design and there is no reduction gear in it, but at the same time it provides a constant distribution of torque along the axes.
There is also no center differential, but there is a mechanism for automatically connecting the second axle. It is noteworthy that the same components are used in the design of the mechanism as in the center differential - a viscous coupling or an electronically controlled friction clutch.
A feature of the drive with automatic connection is that the distribution of torque along the axes is done with a different ratio, which changes under different driving conditions. That is, in one mode, the rotation is distributed in proportion, for example, 60/40, and in the other - 50/50.
At the moment, a system with automatic connection of all-wheel drive is promising and is used by many automakers.
Manual transmission
Transmission with all-wheel drive in manual mode (designation - " Part Time”) is now considered obsolete and not commonly used.
Its peculiarity lies in the fact that the connection of the second bridge is carried out in the transfer case. And for this, both a mechanical drive (by means of a control lever for a transfer case installed in the passenger compartment) and an electronic one (the driver activates the selector, and the servo drive connects / disconnects the bridge) can be used.
In such a transmission, there is no center differential, which provides a constant ratio of torque distribution (usually in a 50/50 ratio).
Almost always in cross-axle differentials, locking is used, and forced. These design features provide the highest cross-country ability of the car.
Other options
It is worth pointing out that there are combined transmissions that have the design and operational features of several types of systems at the same time. They were designated " Selectable 4WD» or multi-mode drive.
In such transmissions, it is possible to set the operating mode of the drive. So, the connection of all-wheel drive can be carried out both in manual and automatic mode (moreover, it is possible to disable any of the bridges). The same applies to differential locks - interaxle and interwheel. In general, there are many variations in the operation of the transmission.
There are more interesting options, for example, electromechanical all-wheel drive. In this case, all the torque is supplied to only one axle. The second bridge is equipped with electric motors, which are activated automatically. Recently, such a transmission has become more and more popular, although it cannot be called a full-fledged system, in the classical sense. Such vehicles are hybrid systems.
Positive and negative sides
Four-wheel drive has a number of advantages over other types. The main ones can be distinguished:
- Efficient use of power plant power;
- Ensuring improved controllability of the car and its directional stability on different types of coverage;
- Increased vehicle traffic.
The advantages are counterbalanced by such negative qualities as:
- Increased fuel consumption;
- The complexity of the drive design;
- Large metal transmission.
Despite the negative qualities, cars that have all-wheel drive are in demand and are very popular even among motorists who almost never leave the city.
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