Permanent four-wheel drive: description, device, pros, cons

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:42

At the very beginning of the development of the automotive industry, car manufacturers experimented, trying to “throw out” types of car models that satisfied the needs of mankind on the market. Either the body will be presented, or the convertible or coupe. Running remained unchanged for a long time. A successful result of numerous tests, progressive engineering was all-wheel drive. A person who intends to purchase movable property doubts which drive to give preference to: decide on the rear, buy on the front, or is it better to opt for an all-wheel drive? Experts will help to resolve it, giving a detailed answer to a given topic. Buy a vehicle with plug-in or permanent all-wheel drive? The description in our article will help you decide.

General patterns

Within the framework of a capacious concept, a structure is meant where the torque coming from the checkpoint is given to all four wheels. What does this give the purchaser?

• Be able to get out faster when stuck in mud.
• Improves the dynamics of the vehicle, the start is madefaster.
• On a sliding highway, such an arrangement adds stability to the horse.

How to resolve the dilemma: permanent or plug-in four-wheel drive to choose? To do this, you need to take a closer look at both mechanisms.

Special AWD Secrets

Looking at the description of the plug-in all-wheel drive, we can note the advantage: the gearbox is able to function in two ways. One of them involves the transfer of torque only to the rear axle, the second - to both at once, allowing you to increase grip with the road surface. Management is carried out thanks to electronics. Such a device scheme underlies the creation of crossovers. Their format, regardless of size, implies the operation of the operational inclusion of additional driving wheels without the participation of the driver, in automatic mode. In order to implement such solutions, the engineers decided to introduce multi-plate clutches, periodically able to drive the rear axle to the steadily spinning front discs.

A pair of gears, an output shaft, plus a transfer case with a reduction gear suitable for climbing uphill, makes the driving much easier, the ride is more comfortable. It turns on forcibly: the driver selects the desired mode on his own using the selector. The task of the servo is reduced to the implementation of normal switching. The mark given by the AWD manufacturer denotes all-wheel drive vehicles.

What does the term "permanent four-wheel drive" mean?

Until the 1980s, these systems were installed exclusively on SUVs, which cannot be said about today: a description of permanent all-wheel drive can be found in the instructions for cars. Synchronization with the axles occurs due to the operation of the differentials. Three differentials are usually mounted, contributing to driving comfort without resistance to movement. The interaxle differential mechanism is the main element that takes on the entire load.

To increase the cross-country potential on some brands, as can be seen from the description of permanent all-wheel drive, a forced differential lock is used, which makes them identical with foreign cars on which the plug-in drive is designed. In some cases, developers prefer to equip the center differential with electronic control. Why is this scheme used?

On virtues

Electronic circuits help coordinate the functionality of the entire node. Their "mission" is to receive signals from sensors that measure the speed of rotation of the rims, instantly change the power parameters depending on road conditions, driving habits. The device of such a plan is considered to be the most progressive due to the provision of high safety indicators for road users. Also, electronics, as follows from any description of permanent all-wheel drive, can improve the dynamics of vehicles. Sedan, hatchback, station wagon are characterized by stability on the road in any naturalconditions, be it snow, heavy rain, hail, strong wind. Is it really that good?

Design flaws

Technicians are trying to upgrade the received systems, come up with something new to improve the ride quality. Improvements would not hurt because of the following disadvantages.

1. On crossovers with permanent all-wheel drive significant fuel consumption, which is not encouraging. It is consistently higher compared to monodrive machines.
2. Repair, maintenance is far from cheap. The complexity of the device adds to the difficulty of finding original parts. Gear replacement is often required, this hits the pocket of an ordinary car enthusiast with an average income.
3. A large number of nodes adds weight: the vehicle becomes heavier, making it more difficult to pull it out of the mud, steering in general.
4. Car owners are interested in the question of whether it is possible to get into an accident on a permanent four-wheel drive. It is not always convenient to drive on a slippery road. Yes, it rides quite stably, but if it “carried”, it is difficult to keep it in place. This is especially true for beginners. Experts recommend in this situation to release the gas pedal, to manipulate the steering wheel. According to drivers, on some models it was completely necessary to face the failure of the normal operation of the “swallow” during snow drifts.

Full-time issues

The owners of crossovers often have the question of whether it is possible to permanentlydrive to avoid slippage. When slipping on one axle, the second one is automatically turned off, and the center differential is responsible for this. In practice, it looks like this: the wheel is turned off, the “steel horse” moves forward a little, and turns on again. To improve the passable qualities, the best solution is to install two forced locks.

To improve the handling abilities of a car with permanent all-wheel drive, self-locking differentials, like Torsen, "viscous couplings" were invented. The goal is to add comfort to driving on an asph alt track. When one of the axles slips, a self-locking device is activated. Thus, the influence of the differential on the second axle is reduced to zero. The inquisitive mind of engineers contributed to the emergence of traction control systems, structures that distribute torque. An expensive sedan or SUV is equipped with such systems more often than budget modifications.

Another headache for servicemen and car owners arises from problems in the systems of viscous and friction clutches. There is a high chance of overheating. The same goes for Torsen. The catch is in its overheating gears. For its cooling, an acute dependence on graphite oil appears. The difficulty of repair is manifested in the location of the differential in the transmission. In the case of the “robot”, the analysis of mechanisms is inevitable. It happens that the meter “jumps”.

The normal operation of the drive is dictated by the uninterrupted performance of the functions of the box. Interruptions in the ECU are fraught with the upcoming troubleshootingtransmission unit.

Problematic link complete with permanent all-wheel drive is considered to be "razdatka" due to severe operating conditions. "Illnesses" with the computer due to adhering dirt particles, enveloping the electrical wire in a dense layer, are not excluded. An important reason to visit a car service “results” from problems with lubricants. Wear of parts leads to contamination of the oil with metal chips. Aged seals, bridge seals often leak. An increase in bearing wear with increasing mileage is inevitable.

A little about the rules

Car consumers are thinking about whether it is possible to constantly drive all-wheel drive and what mechanics advise. It is no secret that in order to master the technique of riding such devices, considerable experience and skills are required. A profitable solution for solving problems is to find a good karting track at the beginning of the development of an unusual "iron horse". It is necessary to provoke drifts, to find different ways out of a difficult situation: with gas, without it, with a steering wheel. Some try out on specially prepared ice. Such actions will help to settle down to your device.

The answer to the above question is ambiguous. Reading autoforums, the thought does not leave that this is not necessary. Servicemen adhere to a similar opinion: the front axle will quickly “fly”. It is recommended to drive in cars with permanent all-wheel drive only on slippery roads, in difficult off-road conditions. Driving on smooth road surfaces without flaws will "kill" the node ahead of time.

Recommended to whom?

Movement on a permanent all-wheel drive is justified only for the "gourmet" racing motorways. With moderate behavior, it is more appropriate to turn to the plug-in mechanism as an addition to the belay devices. Adherents of outdoor activities would be nice to take advantage of the "hard" inclusion, locking the main differential and downshift transmission. It is not recommended to abuse trips over potholes with such technical nuances. Timely oil change, technical inspection will warn against disaster.

The list of all-wheel drive cars includes Audi, Subaru and many other imported products from foreign auto industry.

Toyota Tricks

What is characteristic of Toyota's permanent all-wheel drive? In this regard, one of the elementary methods has been introduced here - the front axle, rigidly connected. Reduced planetary gear facilitates movement. "Distribution" is carried out by a lever. Mechanical clutches connect the front drive shafts. The advantage of the structure lies in the structural simplicity. The “fat” minus of the 4WD format is the possibility of operation only on a sliding surface.

When installing, balance the forces between the drive wheels. This is due to the greater load experienced by the outer wheel on long stretches of routes compared to the inner one. The axle differential acts as a balancer. It is designed to transmit torque to the two wheels of the drive system. The angular velocity of each of them matters. System"Thorsen" focuses on the gear-screw drive. It is calculated with a greater or lesser blocking factor.

In winter, the difficulty is this: one wheel turns, the other stands on a rough surface. The differential of this plan is not suitable as an interaxle option, since the opposite effect is needed here. Emphasis should be placed on the formation of a force capable of moving the car. It's impossible to guess ahead of time. In this regard, automatic distribution will be required. This led to the release of new cars with a built-in Torsen differential. Its essence is the uniform distribution of traction along the axes at the time of the difference in wheel rotation speeds. Working gears partially overlap the shafts. The wheel with the best grip on the ground takes over the torque transmitted by the shafts.

Useful repair information

Trust professionals to repair, because the problematic list of permanent all-wheel drive is not short, deep knowledge is needed. To begin with, experts will take diagnostic measures. Let's analyze a common problem using the Volkswagen Tiguan as an example after an impressive run. In the auto repair shop they meet with the need to replace the handout, and the cost of the issue will not please the owner of the "iron friend". A couple of slips - waiting for a car service. For some reason, the four-wheel drive does not work? What happened? The reason is dirt and moisture that have done their job: when checking the driveshaft, it turns out that it does not rotate with the front wheels, but stands still. Next, the distributing unit is removed. A picture emerges - the slots are simply “licked off” withtransmission clutch due to the slightest slip. A similar thing happened with the slots on the automatic transmission. The price of troubleshooting is from twenty thousand rubles. On "SUVs" it is better not to skid, not to travel along gullies, they are not intended for this. The way out is to carry out preventive maintenance, change the oil every 30,000 km, otherwise there is a high risk of getting a front-wheel drive from an all-wheel drive model.

The Haldex coupling pump was recognized as the weak link. The cost of the pump is rather big, more than two hundred thousand rubles. Close attention should be paid to replacing the lubricant on Haldex without a filter to extend the life of this important part. Clutch elements subject to wear include friction clutches. The purity of the mesh serving as a coarse filter greatly affects the operation of the all-wheel drive. After 120 thousand km of run, it is impossible to say about its cleanliness.

When is there a reason to go to the service station?

Experts advise paying attention to a number of signs:

• The first "call" for a speedy response is the incorrect operation of the entire node.
• Feel like hitting the back of the bumper when cornering.

A clogged mesh leads to an increase in loads, currents, and a reduction in the life of the part. On the fifth generation clutch, the oil changes once every 60,000 km. The oil pan needs to be flushed, the channels need to be cleaned. Sometimes the coupling is dismantled completely for thorough cleaning. Ignoring the problem leads to its costly replacement, costing over two hundred thousandRussian money or pump. Many car owners immediately prefer to change the pump without spending money on cleaning procedures.