The gears do not operate on traditional gear oils. They are filled with special ATF oil. This liquid is a high-index composition on a mineral or synthetic basis. Such fluids for automatic transmissions make it possible to ensure the operation of systems that monitor and control gear shifting. This fluid also transmits torque from the engine to the automatic transmission. Additionally, ATF oil lubricates friction parts and cools them.
How ATF fluids were created
The first automatic transmission was created in 1938. This design is called Hydramatic. It featured a vacuum gear shift system. This unit was created by Pontiac engineers. Even then the company was part of the auto concern General Motors.
Since before starting any innovative development preferred to check it first and test it in every possible way, new automatic transmission was installed on Oldsmobile. The tests were successful. And already in 1939, “Hydromatic” was installed as an option on the Oldsmobile Custom 8 Cruiser. This option cost $57.
General Motors' role in creating the first ATF
By the end of the 40s, automatic transmissions had become a common part of cars. And it is not surprising that the first ATF oil for automatic transmissions was created by General Motors specialists. This was the world's first transmission fluid specification. It was called Type A. The liquid was created in 1949. Then GM began to develop transmission oils, and later to classify them, putting forward the most stringent requirements for them. Products that were created in General Motots laboratories, due to the lack of competition, became international standard working fluids for any type of automatic transmission.
From to new technologies
In 1957, the already successfully existing specification was revised and it was decided to add one small new application - transmission fluid Type A Suffix A (short for ATF-TASA). 10 years later, specification B was created (this is ATF Dexron-B).
The main ingredient, due to which the liquid had lubricating properties, was blubber - this is fat that was obtained from whales. But then the development of technology in the production of automatic transmissions forced the concern to introduce something new. So, in 1973, a new specification, Dexron 2C, was developed. In 1981 it will be replaced by Dexron-2D. After a barrage of negativity from animal rights activists hit the corporation, as well as after a ban on whale fishing, the company created the innovative formula Dexron-2E in 1991. The difference between this product is that it is created on a synthetic basis. Previously, lubricants were mineral-based.
Birth of Dexron-4
In 1994, the entire world community learned about new specifications, which set out new requirements for the properties of viscosity and temperature characteristics. The specification also implied more improved friction properties. These are Dextron-3F and Dextron-3G. After 8 years, Dextron-3H comes out. But the most modern and most rigid is ATF Dexron-4. Of course, today there are other specifications from the rest automobile manufacturers. These are giants such as Ford, Toyota, Huinday and others.
How is ATF different from other gear oils?
To understand the difference, you need to approach the issue from afar. Cars use oils for engines, gearboxes, hydraulic boosters and ATF oil. What are the similarities between all these liquids? These oils are based on hydrocarbons, which are obtained through the processing of fossil fuels. This gives some similarities in characteristics. All of the above products have lubricating properties and increase slip between rubbing surfaces.
Also, all these liquids have good characteristics heat removal. They are similar in consistency. This is where all the similarities end. This sometimes causes serious mistakes when a novice car enthusiast fills the automatic transmission with manual oil and the power steering with brake fluid.
Basic properties of ATF
ATF oil is one of the most complex fluids in its composition among all lubricating mixtures used in modern car. High demands and standards are imposed on such a lubricant. The oil should have a lubricating effect - due to this, friction is reduced, and at the same time wear in the gearbox elements is reduced. At the same time, the friction forces in friction groups should increase. This will reduce slippage of other components.
Also one of important properties- heat removal. Oil has high performance thermal conductivity and fluidity. In this case, the liquid should not foam during operation. Important point- stability, namely the absence of oxidation processes when heated to high temperatures at the moment of contact with oxygen. Additionally, the oil must have anti-corrosion properties. This is necessary in order to prevent the formation of corrosion on the internal components of the mechanism. Automatic transmission fluid must be hydrophobic (this is the ability to push moisture out of the surface). In this case, it is necessary that the liquid retains its fluidity and hydraulic characteristics. ATF grease has stable characteristics and a high compression ratio over the widest possible temperature range. Another point is the decrease in penetrating ability through the automatic transmission and the presence of dye.
Typical characteristics for automatic transmission lubricants
Let's look at several ATF oil specifications, characteristics and numbers. For Dexron-2 specification kinematic viscosity is 37.7 at 40 C. At 100 degrees the same parameter will be 8.1. For Dexron-3, kinematic viscosity is not standardized at all, as well as for other specifications.
The viscosity of ATF oil according to Brooksfield for Dexron-2 at a temperature of 20 degrees should be 2000 mPa, at 30 - 6000 mPa, at 40 - 50,000 mPa. The same parameter for Dexron-3 will be 10 if the pressure is 1500 mPa. Flash point is not lower than 190 degrees for Dexron-2. For Dexron-3 - this parameter is 179 degrees, but not higher than 185.
ATF oil compatibility
Any oil (no matter whether it is mineral or synthetic) can be mixed without any consequences. Naturally, more modern liquids have improved characteristics and properties. If topped up modern liquid as usual, this will improve the properties of the poured oil. The older the specification, the more low performance she will possess. Also, the shelf life of ATF oil is much lower. Experts recommend changing this liquid once every 70 thousand kilometers. It is worth noting that many modern manufacturers They do not regulate the period for replacing this fluid. It is filled in for its entire service life. But when a car runs for 200 thousand kilometers on one oil, this is not very good. The fact is that the fluid in the automatic transmission is working. It is she who transmits torque from the engine to the wheels. This oil is constantly in action, even when the machine is at rest. neutral speed. Over time, it collects waste products.
These are metal shavings that clog the filter and sensors. As a result, the box stops functioning normally. Now to the issue of compatibility. No brand will ever fully disclose all information regarding the composition and properties of the liquid produced. Often, manufacturers limit themselves only to marketing information and advertising that forces people to buy only a specific product. But often this information is not substantiated. For transmissions with rigid torque converter locking, it is recommended to use fluids with constant friction characteristics.
For automatic transmissions with GTF blocking, products with variable properties should be filled. And finally, regardless of the automatic transmission model, all parts, bearings, gears and other elements are made from the same materials. And that means different types of ATF are not particularly different from each other.
About application features and compatibility
If the oil in the box is changed entirely, then it is best to purchase more expensive product. In this case, it is necessary to take into account constants or variables friction characteristics. If the budget is limited, then even universal oil ATF. Its use will not affect the quality of the box. If liquid is added, then experts recommend using products of a class higher or at least not lower than the one filled. But if its resource has reached 70 thousand kilometers, it is necessary complete replacement. It is advisable to perform additional washing. This operation requires an additional 20 liters of oil. It is not cheap, but, judging by the reviews, this operation perfectly washes out the chips. And its presence, as you know, makes work difficult automatic transmission transmission
So, we found out what ATF oil for automatic transmission is.
I have already touched a little on the acronym “ATF” in the article. But today I want to tell you more about it. Let's analyze all aspects of the meaning, decoding, why it is categorically different from fluids in a manual transmission, and how it works. There are really a lot of questions, even a trivial one: is it a liquid or is it oil? Let's find out...
Let me start with a definition.
ATF ( Automatic Transmission Fluid ) – stands for liquid for automatic transmission(machine gun). It is used only in “torque converter” automatic transmissions, also in some CVTs; it is practically not used in robots. Serves to lubricate internal components, as well as transmit torque from the engine - through the transmission - to the wheels.
I read on some forums that they call the “blood” of a machine gun, because the liquid is really red.
Is butter not butter?
Let's start with the easiest question: what is this oil or not oil at all? Guys, this is liquid transmission oil, it is much thinner than, say, mechanical transmissions. This is said by many features: here the torque is transmitted using a torque converter, but as we have already discussed, it is necessary high pressure- fluid oil. Due to its high fluidity, it is usually called a liquid.
For example, transmission oils for mechanics have viscosity tolerances and are divided into winter, summer and universal. You can often see numbers such as SAE 70W-85, SAE 80W-90, etc., choose for your weather conditions, however, most now use universal ones.
There are no traces of such tolerances on automatic machines! SAE viscosity is not used in these fluids; they must always remain fluid in any weather, and they must also withstand much higher temperatures than their “mechanical” counterparts. ATF fluids carry greater loads, this manifests itself in lubrication, protection of components from contamination and oxidation (rust), and also from overheating.
So the mechanics can heat up to 60 degrees Celsius during operation.
But the machine often works with temperatures of 90 – 110 degrees. For example, Chevrolet automatic machines can heat up to 120 degrees.
That’s why cooling radiators are installed on machines so that the oil doesn’t burn when high temperatures. So it is an oil, but it is not the same as the other two, transmission-mechanical and engine.
Why bright red?
As we have already discussed above, ATF oils are not like any other type of lubricant. And therefore you can’t fill it anywhere else, if you confuse it there may be serious damage. Also vice versa - if you pour a regular “manual transmission” into an automatic transmission. This is almost instant “death”. And such cases happened, often they poured engine oil and after a few kilometers the automatic transmission stopped.
To avoid such incidents, it was customary to paint the ATF red - that is, this is nothing more than a simple difference, nothing more. Well, think for yourself, you will never pour red liquid into the engine, although anything can happen...
How does it workATF fluid?
I have already touched on several aspects of the work, but now I would like to talk in detail about how it works.
Temperature
Average working temperature liquid is about 80 - 95 degrees Celsius, although at some moments, for example in traffic jams in the summer, it can heat up to 150 degrees. But why? It's simple - the automatic machine does not have a rigid transmission of torque from the engine to the wheels. Therefore, sometimes the engine gives increased power, which the wheels do not need to overcome road resistance - excess energy must be absorbed by the oil and spent on friction, hence the heating in traffic jams is simply enormous.
Foaming and corrosion
Large masses of oil that move under enormous pressure create a favorable environment for ATF fluid to foam. And in turn, this process leads to oxidation of the oil itself, and metal parts. Therefore, the liquid must have necessary additives to minimize these processes. Moreover, the additives selected are different each time; there are no identical ATF oils. All because internal structure Automatic transmissions are different everywhere, in some devices there is more metal, in others there is metal - cermets, in others there is steel - bronze, this must be taken into account.
Liquid life
As you understand, this liquid is essentially unique; it works in very unfavorable conditions, however, even at such temperatures it can operate for many thousands of kilometers. Its resource is approximately 50 - 70,000 kilometers. However, do not forget that it does not last forever, and after 70,000 kilometers its properties are lost, replacement is required.
Evaporation
Not many people know, but ATF oils can evaporate, so some manufacturers install dipsticks (to measure the level) on their machines. The level may drop due to the release of vapors through the ventilation system of the automatic transmission cavities, in simple words through the "breather". Therefore, it is important to monitor the level, this is a kind of mandatory practice.
Why "ATF is so expensive
But really, why can a liter reach a price of 700–800 rubles, while a vending machine often requires about 8–10 liters? But as you understood from above, this is the most technologically advanced liquid, and it evolves every year.
It is much more advanced than motor oil, and even more so than regular transmission oil, hence the prices. However, again, I repeat, it works in an aggressive environment and for a fairly long period of time, 60 - 70,000 kilometers.
This is what it is ATF oil, I think you liked the article. Read our AUTOBLOG, subscribe to updates.
Do I need to change the fluid in an automatic transmission?
If you believe the operating instructions, then in the case of a new car, the “automatic” does not require any maintenance up to a mileage of 100 thousand kilometers. True, skeptic oilmen frown: they say, by 40-50 thousand it would be nice to fill in fresh ATF fluid(Automatic Transmission Fluid) suitable for a specific machine. But along with specialized liquids The so-called “cartoons” are also popular - ATF with the beautiful name Multi-Vehicle (“multi-vehicle”, that is, for different cars), which can be poured into almost any automatic transmission without bothering yourself with searching for branded oil.
It would seem, why are they needed if you can buy native liquid? The answer is simple: for the secondary. They are taken by those who, already on the second circle of the odometer, are driving an “automatic” and have no idea what and when was poured into it. In addition, not every warehouse or store keeps in its bins a bottle that is known to be suitable for your AT. Delivery of liquid to order can take a long time - and “toons” meet many tolerances. So the question here is not at all about price (“toons” are not cheaper), but rather about the speed of solving the problem.
In total, we took eight liquids with the Multi-Vehicle designation for the test. We found checking the “cartoons” very interesting, because with technical point It is very difficult to create such a product. It is clear that assessing their versatility in full is an impossible task: the number of requirements, tolerances and specifications for ATF exceeds a hundred (both car manufacturers and gearbox manufacturers are trying). Therefore, we have combined all kinds of criteria into groups that are closer and more understandable to the consumer.
These are the parameters by which we will check them.
1. Friction losses in the gearbox. I wonder if the driver will feel the difference or not?
2. The influence of fluid on the efficiency of transferring energy flow from the engine to the transmission. Dynamics and fuel consumption depend on this.
3. Cold start.
4. Protective properties liquids. Based on the rate of wear of the friction pairs, we will estimate the proximity of repair or, God forbid, replacement of the box.
HOW WE CHECK
We measured the main physical and chemical indicators - viscosity and viscosity index, flash point and pour point - in a certified laboratory. Friction and wear losses were assessed using a friction machine - a device that simulates the operating conditions of various friction pairs. The tests were carried out in two stages. At the first, a model similar to a gear was studied. At the second stage, operating conditions in bearings were simulated. At the same time, friction coefficients, oil heating, and wear of friction pairs were measured. Wear was determined by accurately weighing the parts before and after the test cycle, and for the bearing model - also by the hole method. This is when, before testing, a hole of a fixed size is cut on the working surface of the sample, in the area most susceptible to wear, and at the end of the tests, the change in its diameter is recorded. The more it increases, the higher the wear.
Tests for each fluid at one and the other stages lasted a long time: one hundred thousand load cycles for the bearing model and fifty thousand for the gear model.
GINGERBREAKERS GIVEAWAY
So, let's see what happened. It immediately caught my eye that the effect of the fluid brand on the friction coefficient was very ambiguous. For the gearing model, all differences were within the measurement error limits. The Dutch NGN Universal ATF looks a little better than others. But for the bearing model everything is different - the range of the measured parameter is quite large. Here best performance- for Motul Multi ATF and Castrol ATF Multivehicle fluids.
How critical is the difference in this parameter? On a scale of everything power unit(engine and gearbox), the share of friction losses in the gearbox is not so large (if you do not take into account the losses in the torque converter). But the heating of the oil due to friction when working at different liquids differs much more significantly: the average cumulative difference for the gear and bearing models is approximately 17%. From the point of view of the temperature effect, this difference is very noticeable - up to 10–15 degrees, which gives a change in the efficiency of the torque converter by a noticeable few percent. Motul synthetics look better than others here. NGN Universal and Totachi Multi-Vehicle ATF fluids are only slightly inferior to it.
Heating a liquid also affects its viscosity: the greater the heating, the lower it is. And with a drop in viscosity, the efficiency of the torque converter decreases. Many people remember problems with the “automatic machines” of not very young “French” cars, when due to the increase in fluid temperature (especially in summer in traffic jams) they refused to work at all!
Go ahead. It is very important that the dependence of viscosity on temperature is as flat as possible. One of the main criteria for this flatness is the viscosity index: the higher it is, the better. Here the leaders are Mobil fluids Multi-Vehicle ATF, Motul Multi ATF and Formula Shell Multi-Vehicle ATF. The “cartoon” of the NGN brand was not far behind them.
Let's see how much the viscosity of the liquid in the working area of the box changes, taking into account its heating. The difference is noticeable! For kinematic viscosity it reaches 26%. And the efficiency of “automatic machines” (especially older designs) is quite low and is largely determined by the efficiency of the torque converter - which is precisely what suffers when the viscosity decreases working fluid.
The smallest drop in viscosity was found in Motul oils Multi ATF, Formula Shell Multi-Vehicle and NGN Universal ATF. The largest is for Totachi Multi-Vehicle ATF. These are, of course, comparative results; direct transfer to the efficiency of the box cannot be made. But for forced engines, in which the load on the automatic transmission components is higher, it is preferable to have fluids with more stable characteristics.
Low-temperature properties were assessed using a combination of several parameters. Obviously, all liquids, including ATF, thicken in the cold. This means that with a significant minus overboard, excessive viscosity will interfere with cranking the engine at the start, since cars with automatic transmissions do not have a clutch pedal. Therefore, we determined the kinematic viscosity of each sample at three fixed negative temperatures. In addition, we estimated the temperature at which the kinematic viscosity of the oil will reach a certain fixed value, conventionally accepted as the limit at which it is still possible to “crank” the gearbox.
At the same time, we determined the freezing temperature: this parameter is included in all ATF descriptions and indirectly indicates on what basis the liquid is made - synthetic or semi-synthetic.
Synthetics with high index viscosities: Motul Multi ATF, Mobil Multi-Vehicle ATF, NGN Universal ATF, Formula Shell Multi-Vehicle. They also recorded the most low temperatures solidification. And finally, the protective functions of liquids, that is, their ability to prevent wear. We examined the wear of two models - gearing and sliding bearings, since in a real gearbox the operating conditions of these units differ markedly. Therefore, and ATF properties, ensuring wear reduction, must be different and linked to the operation of the torque converter. And here we found a scattering of results. The leader in minimizing gear wear is Mobil Multi-Vehicle ATF, and in the competition on plain bearings, Motul Multi ATF and Totachi Multi-Vehicle ATF won by a wide margin.
TOTAL
If during traditional examinations of gasoline and motor oils As a rule, we identified only minor differences between one sample and another, but here the situation is different. In terms of key parameters, the difference between different ATFs turned out to be significant. And if you consider that the degree of influence of this complex fluid on power, fuel consumption, and the resource of the box is very noticeable, then you should think about its choice. Good synthetics with a high viscosity index is the best choice, which will protect your nerves during a winter start in fairly frosty weather, and will not create problems after a long stay in a traffic jam under the sultry sun.
The extent to which Multi matches its name will be left to the conscience of its developers. At the very beginning, we noted that it is unrealistic to test in practice every ATF in all the “machines” listed on their labels. By the way, in the descriptions (with a few exceptions) tolerances are either directly or by default designated by the word meets, that is, “corresponds.” This means that the properties of the liquid are guaranteed by its manufacturer, but there is no confirmation of compliance by the manufacturer of the car or box. In conclusion, we would like to inform you that if the planned service life of a new car does not exceed 50–70 thousand kilometers (then a replacement is planned), then you read the article in vain - you will not have to change the “liquid clutch”. In other cases, the information we have obtained should be useful. Adding up the results obtained in all tests, we found that the best products were Motul and Mobil, with Formula Shell liquid lagging behind slightly.
Our comments on each drug are in the captions for the photographs.
WHAT SHOULD THE ATF BE?
There is no more complex and controversial device in a car transmission than an automatic transmission. It combines two units - a torque converter, which ensures a continuous flow of energy from the engine to the wheels, and a planetary gear change mechanism.
A torque converter is essentially two coaxial wheels: a pump wheel and a turbine wheel. There is no direct contact between them: the connection is carried out by fluid flow. Coefficient useful action This device will depend on a lot of parameters - the design of the wheels, the gaps between them, leaks... And of course, on the properties of the liquid located between the wheels. It acts as a kind of liquid clutch.
What should its viscosity be? Too much will increase friction losses in the box - a fair share of the power will be consumed and fuel consumption will increase. In addition, the car will become noticeably slow in the cold. Too low a viscosity will dramatically reduce the efficiency of energy transfer in the torque converter and increase leakage, which will also reduce the efficiency of the unit. In addition, the viscosity of a liquid increases greatly in cold weather, and decreases with increasing temperature - the difference can be two orders of magnitude! The liquid can also foam and contribute to corrosion of box parts. It is desirable that the liquid retains its properties for a long time: then you can not look into the box for years.
That's not all. The same fluid must work in the torque converter, in the planetary mechanism, and in the bearings of the box, although the tasks and operating conditions in these mechanisms differ sharply. In the gearing, it is necessary to prevent scuffing and wear, effectively lubricate the bearings and at the same time not interfere with their work with excessive viscosity: after all, with increasing viscosity, friction losses increase. But the efficiency of the torque converter also increases with more viscous fluids.
So many parameters! Consequently, a complex compromise of the properties that the ATF must combine is required.
ATF - LIQUID OR OIL?
The classification classifies ATF as transmission oils, but its purpose is much broader. After all, lubrication of transmission elements - gears and bearings - is not the only (albeit important) function here. The main thing is that ATF acts as the working fluid of the torque converter. It is this fluid that transmits the flow of power from the engine to the transmission, therefore the properties of this fluid are very important for the efficiency of the automatic transmission.
ATF passports standardize its viscosity (at operating temperatures and at negative temperatures), as well as its flash point and pour point, and its ability to form foam during operation. After all, it is viscosity that ensures lubrication and, therefore, the performance of gears and bearings, and the efficiency of transmitting torque from the engine to the transmission.
WHAT ARE THE PROBLEMS?
ATF fluids are very capricious. Not always modern ATF may fit an old machine of the same brand. The same applies to interchangeability: say, an automatic transmission from a Japanese manufacturer in 2006 on a specialized ATF, addressed to a modern German, may not feel good... Lubricate gear wheels and the bearings will be so bad, but the torque converter may get offended and go on strike. Therefore, each automatic transmission manufacturer is looking for its own solution to the problem. And the more difficult it is to make a universal “cartoon” that suits everyone.
