Toyota automatic transmission oil temperature increased. Overheating of the automatic transmission (automatic)

16.10.2019

The automatic transmission has greatly simplified the process of driving. The standard automatic transmission is quite simple to operate and unpretentious to use. With proper care, it can work for a long time without any complaints. But if the driver does not follow the box, it may fail for a banal reason, for example, due to overheating. It can lead to tangible problems in the operation of the automatic transmission, which will require costly repairs or replacement of the unit.

Table of contents:

At what temperature should the automatic transmission operate

The automatic transmission contains ATF, which acts as a torque-transmitting link between the engine and the wheels. During the operation of the automatic transmission, the transmission fluid is heated, from which other elements of the gearbox can heat up. This can lead to final overheating if used improperly.

It is believed that the optimum ATF temperature for automatic transmission operation is between 65 and 100 degrees Celsius. If the temperature of the liquid in the box is exceeded, there is a high risk of damage to its components.

Please note: Specially for cooling the ATF fluid in modern cars, a radiator is used through which the fluid flows and cools.

What causes automatic transmission fluid overheating

As noted above, overheating of the ATF fluid in an automatic transmission can lead to a number of serious problems. Consider the most common of them:

As you can understand, automatic transmission fluid overheating is extremely dangerous and can lead to various problems.

How to detect automatic transmission overheating

An overheating automatic transmission is accompanied by the following symptoms:

The automatic transmission “kicks” when shifting gears - jolts and jerks are felt, which were not there before;
Transfers are switched at the raised turns;
Gear shifting is not always timely;
Some gears may not be included, for example, from the second box it will immediately jump to the fourth;
The overheating icon on the dashboard is on;
There is a smell of burnt ATF.

On some car models, it is possible to find out basic information about the operation of the nodes through the on-board computer. Among this information is often the temperature of the fluid in the gearbox. As noted above, if the temperature exceeds 100 degrees Celsius during operation, this indicates overheating.

Please note: On cars that do not have the automatic transmission fluid temperature control function by default, you can install a special diagnostic device, for example, ELM 327, which allows you to monitor the main parameters of the car, including the temperature in the automatic transmission.

Causes of automatic transmission overheating

Most often, automatic transmission overheating occurs for one of the following reasons:

Problems with automatic transmission fluid. If ATF does not change over 150-200 thousand kilometers (depending on the resource of the filled liquid), it begins to perform its functions worse. Over time, the additives in the liquid burn out, various debris appears in the liquid itself, and a precipitate forms. As a result, the circulation of such liquid becomes difficult;
Radiator problems. As noted above, automatic transmissions use a radiator to cool the ATF fluid. If it does not perform a function, for example, it is very dirty, this will lead to cooling difficulties, which will result in overheating of the box;
Many motorists know that it is not recommended to tow cars with automatic transmission, and it is also not recommended to act as a towing vehicle if your car has an automatic transmission. This is due to the fact that when towing a car, the automatic transmission may overheat and the wear of the box may increase;
Slip. Another problem that seriously harms the automatic transmission. If the car slips in place at high speeds, this leads to a strong heating of the box.

Please note: Many modern cars have protection against automatic transmission overheating, and the box turns off when it gets too hot.

The most popular automatic transmission is a regular automatic, abbreviated as automatic transmission. These are fairly reliable units (especially options). But they have several weaknesses, and if you do not follow the operating rules, then you can very quickly “ditch” this transmission, and the cost of a new one or repairing this one is just HUGE money! One of the detrimental causes is overheating. It is about him that I want to talk more today. As usual there will be a text version + video. So let's read and watch...

Overheating can very quickly disable your automatic transmission, and overheating may not even be noticeable, and at low speeds in the city (for example, you move in gentle modes), you won’t even notice it, and when the machine starts to kick then it will be too late. Today we will talk about the causes and symptoms, and the consequences too.

Normal automatic transmission temperature

The machine is heated by transmission oil (it is special, called -). This fluid is a transmission link - in simple words, it transmits from the engine to the wheels. All this happens in the torque converter, when one turbine (turbine wheel) conditionally tied to the engine transmits oil pressure to another turbine, which is tied to the transmission.

As you understand, it is the oil that heats up, and not the automatic transmission itself, and this heat already heats up everything else.

In order to level the excess heating of the liquid in the machine, it is passed through a cooling radiator, it is precisely because of this that destructive heating does not occur.

It is worth noting that the normal temperature of the oil inside an automatic transmission is between 65 and 95 degrees Celsius. If the temperature exceeds 100, and even more so over 110 degrees, then you already need to think and look. Otherwise, breakdowns are near

Now let's think about what could be the reasons why the machine overheats.

Causes of overheating

The reasons are often banal and everyone can face them:

Clogged cooling radiator . Usually it is separate, located next to the main engine cooling radiator. Over time, it can become clogged with fluff, dirt, insects, etc. IMPORTANT! Clean it every year (at least rinse with not very strong jets of water)

Haven't changed oil in a long time . Let's say they rode 150 - 200,000 km and never climbed into the automatic transmission. A VERY large amount of dirt accumulates, and it can already clog the cooling radiator from the inside. ATF fluid will not circulate, that's overheating for you

Towing a car or trailer . From a large towed mass, overheating and more wear can also occur.
slippage . Stuck in mud, sand or snow. If you are slipping in one place, the speed is high, the automatic transmission is overheating. Many cars even have an overheating protection system, it cuts off the machine after critical heating, you have an indicator on the dashboard

There's another reason, but that's what I call planned aging. The point here is this - on some cars, the automatic transmission radiator and the main one for the engine are combined. BUT often now motors can be high-temperature, which

Unless you're pulling trailers in the back and skidding in the mud. It is important for you to flush the radiator and change the oil inside on time

Consequences of overheating

For an automatic transmission, the consequences are the most deplorable? Let's go over the points again:

Oil (or ATF liquid) . Its operating temperature (at the best) is up to about 130 degrees Celsius. If the heating goes higher, then it corny loses its properties and may even burn. And from such burning, a precipitate may fall out, clogging many working parts - solenoids, valve body, etc. At least the performance of your box will be broken
Friction discs (or clutches). I already wrote about them, they are both hard (usually metal) and soft (can be pressed cardboard and other impregnated types of special paper). So, “soft” friction clutches, from excessively high temperatures, can corny collapse.

solenoids. In simple words, these are specialized valves that open the flow of oil to a package of one or another package of friction discs, closing or opening them. So now solenoids can be 50% plastic, and high temperature can simply destroy them

Wiring. Often, special control wires can go to solenoids, and so from high temperatures, they can also melt and collapse.

These are the consequences that can be from overheating of the machine, so it needs to be controlled

Symptoms of overheating

At the very beginning, to all car owners with, I advise you to buy the so-called (I wrote about it in detail, follow the link). You can install the TORQUE program on your phone, install ELM327 into the OBD2 connector and read the readings of many parameters, including the automatic transmission temperature. Next, find out your extreme heating characteristics (it happens in repair manuals) and look at the readings through the ELMKU. If everything is fine, then OK. If the excess, we are looking for reasons

Symptoms may be:

Shock when shifting
Smell of burnt oil
Poor gear changes
Switching occurs at high speeds
The overheating indicator lights up constantly, especially after several abrupt starts
In the most severe cases, gears may not turn on at all.

As you can see, nothing funny.

For the full operation of the vehicle, a number of working lubricating fluids are used, which make it possible to ensure the correct operation of all machine systems. One of these systems is the transmission, for which specialized automotive oil is used. It is used to lubricate the gears found in manual transmissions, as well as for steering mechanisms, drive axles and transfer cases.

Today there are two types of "transmission":

for use in manual transmissions (manual transmissions);
for front- and rear-wheel drive vehicles with automatic transmission (automatic transmission). Also, this type of oil is used for power steering (GUR).

The second category of lubricating fluids allows you to remove mechanical loads, effectively lubricates the elements, removes heat, corrosion products and micro-abrasive particles in the most worn parts. Oils for automatic gearboxes transmit mechanical energy to all hydromechanical transmission complexes. The most stringent requirements are imposed on this category of lubricants (when compared with manual transmission oils).

Mineral, synthetic and semi-synthetic materials are used as the basis for gear oils. As well as for engine oil, when choosing a “transmission”, oil product classifications are taken into account, based on which indicators such as viscosity and quality of the lubricant can be determined. Let's take a closer look at these standards.

SAE gear oil viscosity classification

The SAE index, which indicates the viscosity of gear oil, was developed by the American Society of Engineers. This standard has become widespread throughout the world and today the SAE J306 specification is used to determine the viscosity classification of engine oil for drive axles and manual transmissions. This qualification also determines the temperature range in which the use of a particular lubricant is permissible.

The lowest and highest temperature at which a car can be operated has its own limit, which is estimated:

by the temperature at which the Brookfield viscosity of the liquid reaches 150,000 cP (centipoise);
by the temperature at which the kinematic viscosity of the "transmission" is determined at a temperature of 100 degrees.

Thanks to this, it is possible to determine the load (approximate) that the protective oil film can handle.

According to SAE standards, gear oils are divided into categories similar to motor lubricants:

winter (W, Winter): 70w, 75w, 80w, 85w;
summer (without index): 80, 85, 140, 250.

Multigrade fluids carry both markings, such as SAE 75w-85. These oils can be used throughout the year. As you can see, in this regard, "transmissions" are similar to motor oils, but this does not mean that these petroleum products are used in the same conditions and have the same performance. The same applies to questions about whether it is possible to fill the “transmission” into the engine and vice versa. Engine oil can be used for gearboxes, but transmission fluid cannot be poured into the engine.

Table of ambient air temperature ranges in which gear oils can be used. The most commonly used types of oils are indicated

Minimum temperature at which lubrication of units is provided, °С	SAE class	Maximum ambient temperature, °С
-40	75W-80	35
-40	75W-90	35
-26	80W-85	35
-26	80W-90	35
-12	85W-90	45

API Gear Oil Viscosity Classification

According to the API GL system, oils are divided into quality classes. The main features of the classification are the design and operating conditions of the transmission, additional features are the content of antiwear and extreme pressure additives.

The classification is described in the API document “Designation of operating lubricating oils for manual transmissions and axles. API Publication 1560, February 1976" (API Publication 1560, Lubricant Service Designation for Automotive Manual Transmissions and Axles, February 1976). API quality classes:

GL-1

Oils for gears operating in light conditions.
Composed of base oils without additives. Small amounts of antioxidants, corrosion inhibitors, light depressant and antifoam additives are sometimes added.
Designed for spiral bevel, worm gears and manual transmissions (without synchronizers) of trucks and agricultural machines.

GL-2

Contains anti-wear additives.
Designed for worm gears of vehicles.
Typically used to lubricate the transmission of tractors and agricultural machines.

GL-3

Oils for gears operating under moderate conditions.
Contains up to 2.7% anti-wear additives.
Designed for lubrication of conical and other gears of trucks.
Not designed for hypoid gears.

GL-4

Oils for gears operating in conditions of varying severity - from light to heavy.
Contains 4.0% effective extreme pressure additives.
Designed for bevel and hypoid gears with small axle displacement, for gearboxes of trucks, for drive axle units.
API GL-4 oils are designed for non-synchronized transmissions of North American trucks, tractors and buses (commercial vehicles), for final drives and other gears of all motor vehicles. Currently, these oils are also the main oils for synchronized gears, especially in Europe. In this case, the label or data sheet of the oil must contain inscriptions about this purpose and confirmation of compliance with the requirements of the machine manufacturers.

GL-5

Oils for the busiest gears operating in harsh conditions.
Contains up to 6.5% effective extreme pressure and other multifunctional additives.
The main purpose is for hypoid gears with a significant axle offset.
They are used as universal oils for all other mechanical transmission units (except for the gearbox).
For a synchronized manual transmission, only oils that have a special confirmation of compliance with the requirements of machine manufacturers are used.
Can be used for limited slip differential if they meet the requirements of MIL-L-2105D (in the USA) or ZF TE-ML-05 (in Europe) specifications. Then the class designation has additional characters, for example, API GL-5+ or API GL-5 SL.
Oils for the most loaded gears operating in very difficult conditions (high sliding speeds and significant shock loads).
Contains up to 10% high performance extreme pressure additives.
Designed for hypoid gears with significant axle offset.
Correspond to the highest level of operational properties.
Currently, the GL-6 class is no longer used, as the GL-5 API class is considered to satisfy the most stringent requirements quite well.

New API classes

MT-1

Oils for highly loaded units.
Designed for non-synchronized manual transmissions of powerful commercial vehicles (tractors and buses).
Equivalent to API GL-5 oils but with improved thermal stability.

PG-2 (project)

Oils for transmissions of driving axles of powerful commercial vehicles (tractors and buses) and mobile equipment.
Equivalent to API GL-5 oils but with improved thermal stability and improved elastomer compatibility.

Gear oil viscosity classification according to GOST

The Russian Federation has its own classification, which is also used when determining the characteristics of gear oil, namely GOST 17479.2-85, this standard was introduced both for motor oils and for "transmission oils". It includes viscosity criteria, which are divided into four classes: 9, 12, 18 and 34. It also includes an indicator of the quality of the oil product, which is divided into five groups, according to the gradation, each group corresponds to the API quality standard, for example, TM-1 (transmission oil) equals GL-1, TM-2 - GL-2 and so on.

Thus, if we have the marking TM-5-18 in front of us, then the last digit will indicate the kinematic viscosity of the liquid.

According to GOST 23652-79, there are the following brands of transmission lubricating fluids based on viscosity indicators:

TEP-15 - are made on the basis of an extract of residual and distillation oils. They have anti-wear and depressant additives.
ТSp-10 - contain extreme pressure, depressant and antifoam additives. Such oils are used for heavily loaded gears.
Tap-15V - is made by mixing extracts of residual oils of phenolic purification with distillate oils. Contains anti-seize and depressant additives.
TSp-15K - contains extreme pressure, antiwear, depressant and antifoam additives. Applicable for heavy vehicles, for example, for KAMAZ trucks.
ТSp-14 hyp - includes anti-seize, antioxidant, depressant and anti-foam additives. Used for hypoid gears of trucks.
TAD-17i are universal liquids that are made on a mineral basis. They contain multifunctional sulfur-phosphorus-containing, depressant and antifoam additives.

In addition to viscosity, when choosing a lubricant, it is necessary to pay attention to the performance classifications (API - USA or ZF - European standard), as well as the density of the gear oil. For example, for TEP-15 oil, the density index at 20 degrees will be no more than 0.950 g/cm3.

All these properties can change after a long period of storage of a lubricant for a gearbox. Therefore, it is necessary to remember such points as: the expiration date of the gear oil.

Transmission oil storage conditions

Lubricants for gearboxes have their own warranty period, which is 5 years, and in some cases 3 years. After this period, the additives contained in the fluid lose their properties and, accordingly, such an expired oil will not meet the necessary requirements.

It is worth noting that the period of 3-5 years indicates the shelf life of automotive oil in unopened containers. If you have already opened the bottle, then the shelf life of the liquid will depend on many conditions. In order for the composition to remain effective for a longer time, it is necessary to adhere to the following recommendations:

avoid temperature fluctuations, the liquid must be stored at a constant temperature not exceeding 20 degrees;
oil should be stored in a well-ventilated area, away from direct sunlight;
it is not recommended to pour the lubricant into another container, it is better to store it in the factory canister, with a tightly closed lid;
do not freeze the "transmission" under any circumstances.

Under these conditions, the oil will be stored for the entire declared period.

Some motorists "revive" expired oil with special additives. It is not recommended to do this, since “live” additives may remain in the liquid, and with such a mixture, their amount will change, which, in turn, will no longer meet the standards. In addition, new components may chemically react with old additives, causing their properties to be unpredictable.

Many mistakenly believe that if the "transmission" has changed its color, then this is the main sign of the unsuitability of the fluid. It is not always so. The fact is that in the production process the main parameter is the lubricating characteristics of the composition, so some deviation in color or smell is acceptable. However, if not only the color has changed, but also a dark crystalline precipitate has appeared, and the oil itself has become cloudy, then such a product cannot be poured.

It is also worth saying that storing transmission or engine oil in a barrel or car system are two different things. In the second case, the lubricant is constantly in contact with the environment, resulting in oxidative processes and various deposits. Therefore, even if you poured new oil into a car without a run, this does not mean that you can change it after 5 years. A scheduled oil change for a gearbox depends on operating conditions, but experts recommend changing the fluid every 70,000 km during normal operation of the system and after 25 000 km when driving under special conditions (hot, cold, full load, etc.).

In custody

Some brands of cars do not provide for a scheduled replacement of the "transmission", but, nevertheless, it is recommended to check the fluid level weekly.

As a rule, if the automatic transmission is in good condition and operates in optimal modes, it facilitates the process of driving a vehicle.

At the same time, even on new cars with an automatic transmission, the owner may encounter the fact that. Also, the gear oil in the machine may darken too quickly, etc.

Quite often, the cause of such failures is overheating of the automatic transmission. Next, we will look at how to understand that the automatic transmission is overheating, the reasons why the automatic transmission overheats, and what needs to be done in this case.

Read in this article

Overheating of the automatic box: consequences and signs

So, we note right away that a significant increase in the temperature of the transmission oil in the machine usually manifests itself in the form of certain malfunctions in the operation of the automatic transmission.

Ignoring such symptoms can lead to a reduction in the resource of the unit itself or breakdowns. In other words, in this case, the automatic transmission often fails, after which an expensive overhaul is required or.

We go further. The reasons for overheating of the automatic transmission can be different. First of all, in the unit itself there are a large number of loaded elements that interact with each other. As a result, a large amount of heat is generated, which is removed by the ATF transmission fluid.

It becomes clear that problems in the automatic transmission or gas turbine engine, a deviation from the norm of the oil level in the machine, a decrease in ATF pressure, and the loss of the properties of the transmission fluid itself lead to an increase in the temperature of the automatic transmission. In some cases, the oil in the gearbox is heated up to 120 degrees or more.

Such heating is critical, the oil loses its properties, the unit malfunctions, and the wear of the box increases significantly. The consequences of automatic transmission overheating are manifested in the form of a breakdown, as well as a number of other elements of the gearbox.

In practice, after a couple of tens of minutes, the operation of the automatic transmission in the maximum heating mode will be enough for the unit to fail. For this reason, it is important to promptly identify the symptoms of automatic transmission overheating. In cases where the automatic transmission overheats, signs of excessive heating can be determined independently. If the automatic transmission is very overheated, the transmission can transfer the unit to.

Check or A/T lights up on the dashboard, indicating problems with the automatic transmission. Various automatic transmission sensors detect an increase in temperature, a decrease in ATF pressure, etc. In such a situation, it is not uncommon when the torque converter literally turns blue from strong heating, the automatic transmission wiring is melted, the clutches burn and crumble.

In this case, when the automatic transmission has entered emergency mode, it is optimal to immediately stop using the car and deliver it to the service not on its own, so as not to worsen the situation further. Moreover, if it is supposed to tow without hanging the drive wheels, then you need to separately take into account all the rules and nuances of such towing a car with automatic transmission.

Please note that the machine does not always “fall” into an accident when overheated. Often the box works, the check does not light up, but the temperature approaches a critical point. In such a situation, after the machine reaches operating temperature, the driver usually feels obvious jerks, jerks when shifting, the machine slips, delays gear changes, etc. At the same time on a cold box it works fine.

You need to understand that in the future problems still cannot be avoided, since constant overheating, albeit not critical, significantly reduces the resource of friction clutches, solenoids, can cause deformations, etc. The transmission oil itself, under conditions of increased heating, also quickly loses its properties and becomes heavily contaminated. This means that the owner must constantly check the level and quality of the oil in the automatic transmission.

It is also important to note any changes in the operation of the unit and immediately carry out diagnostics, change the automatic transmission oil and filter in the automatic transmission in a timely manner, use high-quality fluids recommended by the transmission manufacturer itself.

Causes of automatic transmission overheating

If we talk about the reasons why the automatic transmission overheats, the following can be distinguished among the main ones:

Significant loads on the transmission and heavy operating conditions (trailer towing, frequent and long slippage in mud, snow, etc.)
Insufficient regular automatic transmission cooling or problems with the automatic transmission cooling radiator;
Reducing the oil pressure in the machine (dirty channels, filters, breakdown of the automatic transmission oil pump);
Low / high, malfunctions of the control system, problems with solenoids;

At the same time, problems associated with the automatic transmission oil cooler (automatic gearbox heat exchanger) are a common and common problem. The fact is that if the radiator is contaminated with deposits and natural wear products of the automatic transmission, the hot oil ceases to be effectively cooled in the radiator.

Also, failures are possible in the operation of other elements. For example, automatic transmission solenoids are valves that allow ATF to be directed through channels. If the solenoid does not fire in time, this leads to violations in the supply of the working fluid, which lubricates and cools the parts.

How to solve the problem of automatic transmission overheating

First of all, if the box overheats, it is necessary to start with automatic transmission diagnostics. An integrated approach usually allows you to quickly determine the cause and find out why the automatic transmission is heating up.

Often, to eliminate overheating of the machine, it is necessary to clean the valve body channels, change the transmission fluid and filters, and flush the automatic transmission oil cooler. For cleaning, you can use different methods, ranging from the use of flushing and ending with the disassembly of the unit.

Also an effective way to solve problems with overheating is to install an additional automatic transmission cooling radiator with a thermostat. Such a radiator allows you to quickly reach the operating temperature and further maintain the heating of the oil in the machine no higher than 70-90 degrees.

Taking into account the fact that many modern automatic transmissions can normally warm up to 100-110 degrees, experienced car owners install an automatic gearbox additional radiator not in case of urgent need, but in order to prevent and increase the life of the gearbox.