Lorsque les voitures ont gagné en popularité pour la première fois, la propulsion arrière (RWD) était la méthode de propulsion préférée. C'était aussi le seul choix. Mais la traction avant (FWD) a ensuite pris le contrôle du marché grand public en raison de son économie de carburant frugale, de sa traction plus fiable, de son emballage compact et de sa stabilité.
Aujourd'hui, la préférence se déplace à nouveau vers les AWD et 4WD en raison de la demande des consommateurs pour les SUV et les CUV. Bien qu'ils présentent une économie de carburant inférieure à celle des voitures à traction avant, les tractions intégrales et les 4 roues motrices bénéficient d'une traction et d'un contrôle accrus, mais les deux peuvent souvent être confondus en raison de leurs similitudes.
Les technologies modernes ont rendu la différenciation difficile pour la plupart, mais comprendre la différence peut signifier la différence de rentrer à la maison après une longue randonnée à travers Moab ou d'appeler le calvaire pour vous sauver.
Ne vous inquiétez pas, comme The Drive L'équipe d'information dédiée de est là pour démêler les fils et expliquer toutes les différences entre AWD et 4WD.
Les systèmes AWD et 4WD utilisent des pièces différentes. Voici une ventilation rapide des termes, noms et composants associés.
Un véhicule à traction intégrale utilise généralement un moteur, un convertisseur de couple ou un embrayage, une transmission, un différentiel central, un pack d'embrayage, un différentiel arrière et un différentiel avant. Cependant, il existe de nombreux types de systèmes AWD qui utilisent des technologies uniques, comme l'électricité hybride, et des équipements.
Un véhicule à quatre roues motrices utilise un moteur, un convertisseur de couple ou un embrayage, une transmission, une boîte de transfert, un différentiel arrière et un différentiel avant.
Un différentiel est un ensemble d'engrenages mécaniques ou électroniques dans une transmission qui divise le couple en deux arbres ou essieux de sortie pouvant fonctionner à des vitesses différentes. Il peut également être verrouillé ensemble.
Par exemple, un différentiel arrière, qui est relié à l'arbre de transmission arrière, permet aux roues arrière gauche et droite de tourner à des vitesses différentes. Un différentiel central permet aux arbres de transmission avant et arrière de fonctionner à des vitesses différentes, mais offre la possibilité de verrouiller les deux ensemble.
Il existe de nombreux types de différentiels, les plus courants étant ouverts, verrouillables ou à glissement limité.
Sur les véhicules AWD et 4WD, une boîte de transfert est un mécanisme dans une transmission qui est connecté à une transmission, un arbre de transmission avant et un arbre de transmission arrière. Utilisant généralement des engrenages, un système hydraulique ou une chaîne dans le boîtier de la boîte de transfert, la boîte de transfert transmettra la puissance de la transmission aux arbres de transmission pour alimenter les essieux avant et arrière tout en permettant aux roues avant et arrière de se déplacer à des vitesses différentes.
Sur les véhicules à 4 roues motrices, la boîte de transfert peut être actionnée manuellement par un levier, un cadran, un interrupteur ou un bouton pour engager différents réglages de vitesse. Sur les véhicules AWD, la boîte de transfert fonctionne automatiquement sans intervention.
Un système de traction intégrale fournit de la puissance aux quatre roues du véhicule en même temps tout le temps, mais la quantité de couple transmise à chaque roue varie. Selon le système, une transmission intégrale fonctionnera normalement avec une polarisation avant ou arrière. Par exemple, la Subaru Outback envoie par défaut 80 % de son couple à l'avant et 20 % à l'arrière. Cependant, lorsque la traction est nécessaire sur une ou toutes les autres roues, le système canalisera la puissance vers l'essieu qui appelle à l'aide.
Les systèmes de traction intégrale utilisent un type de différentiel central (il en existe plusieurs) qui permet aux roues avant et arrière de fonctionner à des vitesses différentes. Dans certains exemples, comme le Ford Edge, le système de traction intégrale permet de découpler complètement l'arrière pour permettre une traction avant à 100 %.
Traction intégrale à polarisation avant :Le véhicule transmet plus de couple aux roues avant qu'aux roues arrière.
Traction intégrale arrière :Le véhicule transmet plus de couple aux roues arrière qu'aux roues arrière.
Le but des quatre roues motrices est de maintenir une traction optimale lorsqu'elles sont sélectionnées manuellement. Un véhicule a quatre roues motrices lorsque les arbres de transmission avant et arrière peuvent être verrouillés ensemble pour se déplacer à la même vitesse et envoyer la même quantité de couple aux quatre roues. Les quatre roues motrices sont généralement destinées à une utilisation hors route et sur des surfaces extrêmement glissantes.
Une voiture avec 4 roues motrices à temps partiel fonctionne en 2 roues motrices à moins que la voiture ne soit manuellement ou automatiquement commutée électroniquement en 4 roues motrices. Un arbre de transmission est relié en permanence à l'alimentation, tandis que l'autre peut être connecté en cas de besoin. Le 4WD à temps partiel est le plus souvent engagé avec un bouton, un cadran, un levier ou un interrupteur à l'intérieur de la cabine du véhicule. Il s'agit du type de 4x4 le plus traditionnel et on le trouve souvent sur les véhicules 4x4 tels que les SUV et les camions de type Jeep.
Lorsqu'un véhicule est en véritable quatre roues motrices, il ne peut pas rouler normalement sur les routes régulières car les essieux avant et arrière ne sont pas autorisés à fonctionner à des vitesses différentes. En cas de tentative, la voiture pourrait commencer à se coincer ou à frissonner, un phénomène connu sous le nom de « saut de corbeau ». Cela pourrait endommager le véhicule.
Il s'agit d'un type différent de traction intégrale à temps partiel. Une voiture avec 4 roues motrices à la demande fonctionne en deux roues motrices par défaut mais fait automatiquement appel aux autres roues lorsque la traction est nécessaire.
Une voiture avec 4 roues motrices permanentes, parfois appelées 4 roues motrices permanentes ou 4 roues motrices automatiques/automatiques, envoie également 25 % de la puissance à chaque roue 100 % du temps. Cependant, un pack d'embrayage ou un différentiel central permet aux arbres de transmission avant et arrière de se déplacer à des vitesses différentes.
Sur les véhicules 4x4, il y a généralement un cadran, un levier, un interrupteur ou un ensemble de boutons avec différentes configurations de conduite. Each option should be used only in the specific intended circumstances, or the driver risks damaging the vehicle. Below, we explain how to use 2H, 4H, and 4L.
2H is an abbreviation for Two High. This means two wheels are engaged, typically the rear wheels, in high range. Drivers should use 2H under normal driving circumstances on hard surfaces.
4H is an abbreviation for Four High. This means four wheels are engaged in a high range gear ratio. Drivers should use 4H when they need extra traction, such as driving on snow or rocky trails, at average speeds of approximately 30-50 mph (check your vehicle’s manual for exact limitations and specifics).
4L is an abbreviation for Four Low. This means four wheels are engaged in a low range gear ratio. Drivers should use 4L in circumstances when maximum traction and torque is needed, such as in deep sand, mud, or snow. It is also suitable for climbing or descending steep inclines with unstable surfaces. 4L allows for slow controlled speed typically less than 15 mph and greatly helps during off-road crawling.
Electric and hybrid AWD systems operate much differently than AWD systems on traditional gas-powered vehicles. On EVs, there’s no engine, transfer cases do not apply, and mechanical linkages are replaced with computer wires. To operate in AWD, the EV must use electric motors to power both the front and rear axles and all four wheels. Here are a few examples of different types of electric all-wheel-drive setups.
The car features two electric motors. One is located on the front axle and the other is located on the rear axle. Differentials on those axles allow the wheels to spin at different speeds. Teslas call this Dual Motor AWD.
The upcoming electric GMC Hummer is rumored to have three electric motors, likely with one upfront and two on the rear. With two motors at the back, the vehicle could control of each of the rear wheels.
Not all electric cars are built the same. Rather than mounting the electric motors directly onto the axles, some electric vehicles use four independent motors built into the hubs of each wheel. Once again, computers can control how much power, negative or positive torque, and slippage occurs at each wheel.
Examples of AWD electric cars :
Hybrids combine a gas motor with some type of electric assistance. Full hybrids pair gas motors with electric motors. All-wheel-drive hybrids typically use the gas engine to power one axle and an electric motor to power the other to achieve control over all four wheels. In some cases such as the Acura NSX, however, a system will use a gas engine and multiple electric motors.
Examples of AWD hybrid cars:
This depends on how much snow is present, as well as the purpose and mission of the drive. Driving down a snowy highway? Think AWD. Driving over a snow-covered mud field? Think 4WD. Read more in How to Drive in the Snow.
Typically, yes, but some modern systems allow the driver to deactivate AWD to use two-wheel drive.
This depends on how the vehicle will be used and the climate it will be driven in.
This is dependent on the buyer’s needs, locale, and budget. The answer is not always yes.
Yes and no, AWD improves traction in slippery conditions, including on ice. But it only helps propel you forward. It won’t help you corner or stop.
Yes, AWD improves traction in slippery conditions, including when it rains.
AWD adds cost, reduces gas mileage, and has complex components that could falter.
Yes, for two reasons:AWD systems require more energy to power more wheels and add weight due to their more complex makeups.
Technically, yes, but traditionally, no. Select systems allow for the front or rear driveshaft to be fully disconnected.
With the proliferation of AWD throughout the industry and its manufacturers’ lineups, each company has slightly different technologies and uses slightly different marketing terms to describe the systems in its vehicles. Here are some of the most common systems and what they mean, as described by the manufacturers themselves.
“SH-AWD uses dynamic torque vectoring to provide more accurate and predictable handling performance in all road conditions.
Up to 70% of engine torque can be sent to the rear wheels as needed, with up to 100% of that torque apportioned to either the left or right wheels. Further, today's SH-AWD can overdrive the outside rear wheels by up to 2.7 percent, creating additional rotational speed that helps "pull" the car through the turn with increased grip and cornering accuracy.”
“Fundamentally, Quattro all-wheel drive for Audi medium and large cars works similarly to previous systems with three differentials. It is mechanically as well as electronically activated, and it distributes torque to wheels based on steering angle sensors, traction and stability control, yaw sensors (measuring how weight shifts left or right around its center of gravity) and wheel sensors.
Default power distribution is 40:60 front to rear, with up to 70% of power to the front wheels or up to 85% of a vehicle’s power to the rear. Additionally, electronic wheel-selective torque control can assist traction across each axle through individual wheel braking. Torque control is provided by an intelligent software function of the stability control.
In S and RS models, the rear Sport differential has the ability to overdrive the inside or outside wheel, or even send almost all power from one rear wheel to the other, in hard cornering, creating more neutral handling. This is known as torque vectoring.”
“With BMW xDrive, intelligent Dynamic Stability Control (DSC) sensors detect the slightest loss of grip, and using an electronically controlled multi-disc clutch, divert the power to the set of wheels that have the best traction, reacting much faster than traditional, hydraulically operated systems. BMW xDrive is a fully variable system that can send almost 100% of the power to either axle, offering instantaneous and effective transfer of engine power.”
“The HTRAC AWD system was developed as a multi-mode system, providing an electronic, variable-torque-split clutch with active torque control between the front and rear axles. The driver-selectable HTRAC Normal, Sport and Smart modes help provide confident control in all weather conditions. The Sport setting gives a more agile feel by sending more available torque to the rear wheels, for a sporty dynamic feel when desired.”
“Available active on-demand all-wheel drive helps provide enhanced driving performance by actively distributing torque between the front and rear wheels depending on road conditions and driver input. The system utilizes electro-hydraulic AWD coupling to precisely activate the multi-plate clutch plate, constantly redistributing the amount of power transferred to the front and rear wheels.
During normal driving, power is distributed according to the drive mode selected. Eco and Smart modes deliver 100 percent power to the front wheels. Comfort and Snow modes deliver 80 percent power to the front wheels and 20 percent to rear. Sport mode splits the power 65-35 percent between front and back. Lock mode delivers power evenly to all four wheels.”
“Mazda’s advanced i-ACTIV AWD system uses sophisticated real-time vehicle dynamics modeling to help predict the available grip at each tire and sends torque to the wheels that can use it best. The system comes into play before the front wheels lose grip, engaging the rear wheels to deliver traction where and when it counts.”
“At its core, the 4MATIC system feeds power to the front axles through a transfer case in the transmission, while a limited-slip differential provides a balance between front and rear. Sensors manage the torque demands of each wheel, resulting in greater traction and acceleration.”
“The compact and weight-optimized all-wheel-drive consists of a power take-off on the front axle transmission, a two-section propeller shaft, and rear axle transmission with an electro-hydraulically regulated hang-on clutch. The intelligent controller of the ALL4 system is interconnected with the Dynamic Stability Control (DSC) and constantly calculates the ideal power distribution ratio between the front and rear wheels. This means that the outstanding engine power is always channeled to the place where it can be most effectively and efficiently translated into driving fun.
In normal driving conditions with the DSC activated, it transmits the drive torque in a brand-typical manner to the front wheels. But if the DSC controller detects a danger of slip on the front wheels, the hang-on clutch will transfer the drive torque to the rear wheels with the aid of an electrohydraulic pump.”
“The new lightweight S-AWC electronically distributes driving torque between the front and rear wheels, along with Active Yaw Control (AYC). The new system offers enhanced tracking performance through cornering, and improves vehicle stability and steering response through the use of a yaw control sensor that precisely controls vehicle yaw rate by applying brake pressure on an inside wheel to pull the vehicle back into line for improved vehicle stability and dynamic composure.
Additionally, a driver-selectable push-button allows drivers to select from four distinct driving modes – the standard Normal mode, enhanced feel in slippery conditions with the Snow setting, maximum control in Lock, and an AWC Eco mode that maximizes fuel efficiency by prioritizing drive to the front wheels and still switches in a split-second to all-wheel drive when multiple sensors determine its necessity.”
“The principle philosophy for any Porsche with active PTM is the same:Enhanced driving dynamics, improved driving safety, and increased traction for an even sportier driving experience. It distributes drive torque between the front and rear axles actively and very quickly.
Permanent monitoring of driving status means PTM can be actively pre-set to respond to different driving situations:For example, sensors continuously monitor the speeds of all four wheels, the longitudinal and lateral acceleration of the vehicle, as well as the steering angle. By evaluating all sensor data, it is possible to adjust the distribution of propulsion force to the front axle as quickly and effectively as possible.”
“The Subaru Symmetrical AWD system is designed to optimize both traction and balance. The entire system lies along the centerline of the vehicle, balancing weight distribution between the two sides to help provide optimal performance and control. The system sends power to all wheels simultaneously for maximum traction and acceleration. In slippery conditions, that power is actively distributed to the wheels with the best traction.”
“The Camry and Avalon AWD system can direct up to 50 percent of engine torque to the rear wheels, in response to acceleration from a start or slippage at the front wheels. Notably, when AWD isn’t needed, such as on long highway stretches, the electromagnetically controlled coupling on the front of the rear-drive axle can disengage the propeller shaft from the differential to prioritize fuel efficiency. The AWD is designed to re-engage in an instant when needed.”
“On all MQB (modular transverse toolkit) models with the 4MOTION all-wheel drive system, power is distributed between front and rear axles on an infinitely variable basis by a multi-plate clutch. Normally, power is mainly transmitted to the front axle, which saves energy. However, in the event of an impending loss of traction, the rear axle is activated in a fraction of a second. This is why 4MOTION is considered to be a permanently engaged four-wheel-drive system.
The distribution of power to all four wheels becomes active before wheelspin occurs. A loss of traction is therefore virtually excluded. There is no fixed distribution of power. Power distribution is continuously adjusted to actual driving conditions. However, should any wheel slip, power is immediately transmitted to the wheels where it is needed.”
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