Three types of automatic machines are popular in mass production - hydromechanical, variators and so-called robots.
The first is undoubtedly a classic of the genre. Fundamentally, the design looks like this: gear ratios are changed, braking the necessary friction clutches in the planetary gears (in fact, several independent single-stage gearboxes, each controlled by its own clutch, are assembled in one housing). The process is conducted by a hydraulic unit, including valves and actuators. In modern machines, control was assigned to the electronic brain, capable of processing a large amount of information, optimizing the process. He is also ready to adequately perceive external control actions coming from the driver (manually controlled options such as "Steptronic", "Tiptronic", etc.). The pressure for hydraulics is created by its own pump connected to the input shaft of the gearbox. At the same time, the assembly provides fluid circulation along the lubrication and cooling circuits. Another integral part of this system is the torque converter, the main “non-rigid” device that transmits torque from the engine to the transmission. Among other things, it plays the role of an automatic clutch: the elastic (through the fluid) connection between the gearbox and the engine allows you to keep the car on the brakes at any position of the selector (including “drive” and “reverse”).
Given the experience of serial production (over 50 years), hydromechanical transmission is perhaps the most complete in all respects. The main disadvantage is the complexity of manufacturing and repair, which leads to the high cost of both. The good news is the abundance of consumables and specialized workshops.
And yet, the choice should not be simplified, especially when it comes to a used car. (There is nothing to be afraid of new buyers - for three years they have been living under the wing of a dealer.) Preference should be given to European products - from experience, it is easiest to find the necessary part. Things are worse with Japanese automatic transmissions, which, incidentally, are also installed on machines from other manufacturers. To clarify - the problem is not in the quality of manufacture, but only in the availability of spare parts! The Americans go their own way, mainly offering the consumer already restored KP. The price is acceptable, but the quality of the repair, alas, is unstable - Novo-secular roulette!
Electronics, regardless of "nationality", does not cause complaints - provided that it is reliably protected from dirt and water. Best of all, when the unit is located in the cabin, it’s worse if it is attached to the gearbox housing (no protection will save you here!).
The next type of automatic transmission - the variator is simpler: on the drive and driven shafts of the transmission there are sliding pulleys connected by a variator chain or belt. When changing the distance between the halves of the pulleys, the belt will fall to the center or be pushed to the periphery. By varying the values of the working diameters in this way, the desired gear ratios are obtained. For starting off, an analogue of the clutch is also provided here - a clutch package or the same torque converter. Typically, the mechanical part operates in a fluid with all the “leaking” accessories, including a mechanical drive pump. The electronic control module of the CVTs is no more stupid than that of hydromechanics, and provides the user with a similar set of services (including manual control mode). However, the variator has an order of magnitude less detail, which reduces the likelihood of breakage. But the trouble is similar - to get new shafts and a connecting element with us is almost impossible! The unit restored in Europe costs from 4 thousand euros! So, acquiring a used “variator” car, do not skimp on diagnostics in a specialized technical center.
ON OLD YEAST
The now popular robotic gearboxes are not at all so new - they took root on trucks in the last century. At the heart of the unit is a familiar mechanical box that has received a sequential (sequential) switching mechanism. The on-board computer gives commands to the electromagnetic solenoids connected … with the familiar hydraulic valves! Yes, most often the actuators are squeezing the clutch (here it is present in the classic form - a flywheel, a disk, a basket) and including gears - hydraulic, operating under pressure up to 200 atmospheres. And so, and there is a pump, a working fluid and even a radiator to cool it! Fortunately, the lubrication system of the gearbox itself remained the same, which removed the restrictions on towing a car. The disadvantage is the same - problems with spare parts for "used" copies.
A stranger to the mind
The main advantage of an automatic transmission is not even the ease of operation - this is another step towards an ideal car. Already the easiest machine - a large dock in driving modes. He will select the necessary transmission for you, and he will save fuel, and the engine will save (both from overload and from “torsion”), and he will take care of the environment to the best of his ability. It remains to set the desired mode by putting the selector in a certain position. What does this or that symbol mean is better to follow the instructions - some letters sometimes hide different concepts (S, for example, can mean sport, but more often standard).
The numbers from 1 to 3 indicate the upper limit to which the gearbox can reach at the selected position - first, second or third gear, respectively. The option allows you to slow down the engine (with the desired degree of intensity), since the machine cannot boast of this ability in the “drive”.
On slippery roads do not neglect the "winter" mode. In it, the car moves off from second gear, reducing the risk of slipping of the drive wheels. But any slippage is harmful both to safety and to friction clutches. They do not like the latter and the “sport” mode - if you do not abuse extreme sports, the AKP resource can be easily doubled!
In boxes with an electronic control unit, the need for such intervention "in detail" is reduced thanks to artificial intelligence. Moreover, the current KPs easily adapt to the management style: the addictive cycle lasts from 2-3 to 20 trips. And as a consolation prize, the driver is offered the so-called manual mode. The name is conditional, because the driver does not directly control the gearbox, but only communicates his wishes to the controller. The main thing is not to overestimate your own qualifications: a bad commander is grief for a subordinate.
It is noted that the cost of repairing an automatic transmission increases in direct proportion to the time elapsed from the moment a malfunction occurred to its detection. If you want to save money, be on the lookout, as there are not so many characteristic features. First of all, it is necessary to monitor the state of the working fluid: an unmotivated decrease in its level, the smell of burnt oil, a puddle under the machine is a serious cause for concern. All kinds of slippage, jerking, bumps or delays when shifting gears should also be alarming. Especially beware of all kinds of extraneous sounds - more often than not they indicate excessive wear, but mechanical damage. And in no case do not go out on a car with a burning lamp for automatic transmission failures - these are not uncommon.
But if you’re not so lucky - how to get to the workshop with the least “mechanical loss”? The theory in this regard is simple - any, even short-term operation of a faulty mechanism is not good for him. Therefore, the most preferred tow truck. However, if oil has leaked or the engine does not work (read, automatic transmission pump), there is no alternative to it - hardly anyone decides to disassemble the drives of the drive wheels in order to immobilize the filling of the box. If the engine is in order, you can take a chance by reaching the service in any surviving gear. If none of them turns on, the car will have to be towed, not exceeding a speed of 40 km / h at a distance of no more than 40 km, holding the selector in position “N” (neutral). Here you can only envy the owners of the "robots": they have not written such a law - drag a car where and as much as you like.
But from each rule there are, as you know, exceptions. Therefore, becoming the owner of a car with automatic transmission, do not be too lazy to get instructions or consult a dealer.
When operating an automatic transmission, experts recommend observing several simple rules:
carefully monitor the level and condition of the working fluid. At a low level, the presence of impurities or the smell of a burnt engine do not start;
regularly change fluid and filter in automatic transmissions of any generation. In large cities, the process is better timed to coincide with every second MOT;
apply only the recommended liquid, no mixtures and miraculous additives;
at low temperatures, before starting, warm up the engine to 30–40 ° С (the liquid in the automatic gearbox will warm up “at the same time”);
monitor engine cooling: overheating of the combined radiator will lead to overheating of the oil in the gearbox;
Do not wash the engine compartment under high pressure - the electronics do not like water;
do not abuse towing - in case of breakdown call a tow truck;