Application area

Transmission oil- lubricating oil used to lubricate engines (for example, boat motors), transfer cases, gearboxes, steering mechanisms, main gears of driving axles, as well as gear and chain drives (reducers) of all types.
The criteria for assessing the quality indicators of transmission oils are:

• extreme pressure, anti-wear and anti-pitting properties;
• high antioxidant stability;
• viscosity-temperature properties;
• do not have a corrosive effect on transmission parts;
• protective properties in contact with water;
• compatible with rubber seals;
• anti-foam properties;
• physical stability in conditions of long-term storage.

Types and classification

Gear oils are divided into classes according to the field of application, viscosity and performance. There is also a division according to the method of oil production - synthetic and semi-synthetic.

By field of application:

• API GL-1- Oils for gears operating in light conditions.
• API GL-2
• API GL-3- Oils for gears operating in moderate conditions.
• API GL-4- Oils for gears operating in conditions of varying severity.
• API GL-5- Oils for the most heavily loaded gears operating in harsh conditions.
• API GL-6- Hypoid gears with increased displacement, operating in conditions of high speeds, high torques and shock loads.
• API MT-1- Oils for highly loaded units

By viscosity:

By operational properties:

• Mineral oils without additives
• Mineral oils with antiwear additives
• Moderate performance EP mineral oils
• High performance EP mineral oils
• Mineral oils with EP additives of high performance and multipurpose action, as well as multi-purpose oils

Domestic classification of gear oils is reflected in GOST 17497.2-85.

The designation of transmission oils consists of groups of signs, the first of which means - TM (transmission oil); the second group of signs is designated by numbers and characterizes belonging to the group of oils in terms of operational properties; the third - denoted by numbers and characterizes the class of kinematic viscosity.

Specifications

For the full operation of a vehicle, a number of working lubricating fluids are used, which allow ensuring the correct operation of all systems of the machine. One of these systems is the transmission, for which a specialized automotive oil is used. It is used to lubricate gear joints found in manual transmissions, as well as 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 cars with automatic transmission (automatic transmission). Also, this type of oil is used for power steering (GUR).

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

Mineral, synthetic and semi-synthetic materials are used as the basis for transmission oils. As well as for engine oil, when choosing a "transmission", the classification of petroleum products is taken into account, based on which it is possible to determine such indicators as the viscosity and quality of the lubricant. Let's consider these standards in more detail.

SAE transmission oil viscosity classification

The SAE index, which indicates the viscosity of a 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 at 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:

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

This makes it 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 engine lubricants:

• winter (W, Winter): 70w, 75w, 80w, 85w;
• summer (no index): 80, 85, 140, 250.

Multigrade fluids have both markings, e.g. SAE 75w-85. These oils can be used throughout the year. As you can see, in this regard, "transmissions" are similar to engine oils, but this does not mean that these oil 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 temperature ranges in which gear oils can be used. The most commonly used types of oils are indicated.

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

• Light duty gear oils.
• Consist of base oils without additives. Sometimes antioxidant additives, corrosion inhibitors, light depressants and defoamers are added in small amounts.
• Designed for spiral-bevel gears, worm gears and manual transmissions (without synchronizers) of trucks and agricultural machines.

GL-2

• Contains antiwear additives.
• Designed for worm gears of vehicles.
• Typically used for the lubrication of transmissions in tractors and agricultural machines.

GL-3

• Oils for gears operating in moderate conditions.
• Contains up to 2.7% antiwear additives.
• Designed for lubrication of cone and other gears of trucks.
• Not intended 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 intended for non-synchronized gearboxes of North American trucks, tractors and buses (commercial vehicles), for main and other gears of all vehicles. Today these oils are also used for synchronized transmissions, especially in Europe. In this case, the label or data sheet of the oil must contain an inscription about this purpose and confirmation of compliance with the requirements of the machine manufacturers.

GL-5

• Oils for the most heavily loaded 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 significant axle displacement.
• They are used as universal oils for all other mechanical transmission units (except for the gearbox).
• For a synchronized manual transmission, only oils are used that have a special confirmation of compliance with the requirements of the machine manufacturers.
• Can be used for limited slip differentials if they meet MIL-L-2105D (US) or ZF TE-ML-05 (Europe) specifications. Then the class designation has additional signs, for example, API GL-5 + or API GL-5 SL.
• Oils for the most heavily loaded gears operating in very difficult conditions (high sliding speeds and significant shock loads).
• Contains up to 10% of highly effective EP additives.
• Designed for hypoid gears with significant axle displacement.
• They correspond to the highest level of performance properties.
• Currently, GL-6 is no longer used as API GL-5 is considered to meet the most stringent requirements reasonably well.

New API Classes

MT-1

• Oils for highly loaded units.
• Designed for unsynchronized mechanical transmissions of powerful commercial vehicles (tractors and buses).
• Equivalent to API GL-5 oils, but with increased thermal stability.

PG-2 (draft)

• Oils for transmission of drive 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.

Classification of gear oil viscosity according to GOST

The Russian Federation has its own classification, which is also used to determine the characteristics of transmission oil, namely GOST 17479.2-85, this standard was introduced both for engine oils and for "transmission". It includes viscosity criteria, which are divided into four classes: 9, 12, 18 and 34. It also includes an indicator of the quality of a petroleum 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, then the last figure 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 residual and distillation oils extract. They have antiwear and depressant additives.
• TSp-10 - contain extreme pressure, depressant and antifoam additives. These oils are used for heavily loaded gears.
• Tap-15V - is made by mixing extracts of residual oils of phenolic purification with distillate oils. Contains extreme pressure and depressant additives.
• TSp-15K - contains extreme pressure, antiwear, depressant and antifoam additives. Suitable for heavy vehicles, for example, for KAMAZ trucks.
• TSp-14 hyp - includes extreme pressure, antioxidant, depressant and antifoam additives. Used for hypoid gears of trucks.
• TAD-17i - universal liquids that are made on a mineral basis. They contain multifunctional sulfur-phosphorus, depressant and antifoam additives.

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

All of these properties can change after an extended shelf life of the gearbox lubricant. Therefore, it is necessary to remember such points as: the shelf life of the gear oil.

Storage conditions for transmission oil

Lubricating compositions 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 expired oil will not meet the necessary requirements.

It should be noted that the period of 3-5 years refers to the shelf life of automotive oil in an unopened container. 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 longer, it is necessary to adhere to the following recommendations:

• prevent temperature changes, 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 a factory canister, with a tightly closed lid;
• do not freeze the "transmission" under any circumstances.

If these conditions are met, 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 mixing, their amount will change, which, in turn, will no longer meet the standards. In addition, new components can chemically react with old additives, resulting in unpredictable properties.

Many people 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, therefore, some deviation in color or smell is permissible. 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 must not be poured.

It is also worth noting that storing transmission or engine oil in a barrel or vehicle system are two different things. In the second case, the lubricant is constantly in contact with the environment, as a result of which oxidative processes occur and various deposits appear. Therefore, even if you have poured new oil into a car without a run, this does not mean that you can change it in 5 years 000 km when driving in special conditions (heat, cold, full load, and so on).

In custody

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

In this article, we will look at existing ways to classify gear oils. Compared to engine oils, there are few of them, at least basic ones. First you need to decide on the types of transmission oils, since different transmissions use different oils. So, as a first approximation, we have manual transmissions, which are adjacent to transfer cases and drive axles with differentials in them, and automatic transmissions.

Oils for manual gearboxes

For this type of transmission, there are two main types of classification, which are already familiar to us in ways. These are SAE, which standardizes the viscosity of used transmission oils, and API, which specifies their level of performance. In addition, there is a GOST classification system, as usual, combining the classification of viscosity and quality level.

Classification of gear oils SAE J306

Let's go over SAE briefly, if you need more information, read the article about. So, most gear oils, like engine oils, are multigrade, suitable for year-round use. At least, this is what we hope for by the type of viscosity recording according to SAE 80W-90, 75W-90, or something else like that. We see here both the number of "winter" viscosity (before the letter W - winter, that is, "winter"), and summer viscosity (in this case 90). Since transmission oil works under different conditions than engine oil, different viscosity parameters are determined for it. In the winter figure, unlike a motorboat, the maximum temperature "sits" at a viscosity of 150,000 cPs (and not 60,000, as in engine oil) and a minimum kinematic viscosity at 100 ° C. The illustration shows all viscosity grades of the gear oil.

Despite the fact that the numbers themselves differ (for engine oils, for example, 10W-40, and for transmission oils, 75W-90), their actual viscosity is approximately the same. The numbers were deliberately changed so that motorists did not confuse these oils with each other when filling. Although engine oil, in general, can be poured into a box (this was even recommended by VAZ for front-wheel drive eights and nines at the dawn of their appearance). But not the other way around. The transmission in the engine is completely irrelevant.

API classification for gear oils

The performance level of transmission oils is established by the API grading system. The designation principle is as follows: the numbers from 1 to 6 were added to the letters GL (for now), as the quality of the oil improved. At the moment, the revision of the standard from 2013 is relevant, according to which the classifications are considered valid:

• GL-4 - describes oils for spiral bevel axles operating at medium to hard speed and load conditions, or for hypoid axles operating at medium speed and load conditions. Such oils can be used in manual transmissions (including front-wheel drive vehicles), where MT-1 classification oils are not suitable (that is, non-ferrous steel synchronizers are present).
• GL-5 - describes oils for gears, including hypoid, in axles operating at various combinations of high speed / shock and low speed / high torque. In fact, this oil is better in its properties than GL-4, but its use in gearboxes is limited, since in order to achieve such parameters, an additive is often used that negatively affects the color of synchronizers. Recently, this additive can be replaced with one that is harmless to synchronization, and, accordingly, oil can be poured into the bridges and manual transmissions. Oils with such an additive in the composition have the GL-4 / GL-5 specification.
• MT-1 are oils for non-synchronized gearboxes used in buses and heavy trucks. They have better protection than GL-5 and GL-4 against thermal decomposition, wear of parts and seal materials. Cannot be used in synchronized gearboxes. Also, these oils cannot be mixed with engine oils used in the transmission of tractors (there are universal oils for tractors that are poured into all components from the engine to "wet" brakes and hydraulic drives, for ease of maintenance).

Traditionally, when choosing an oil, you should adhere to the manufacturer's recommendations. There is also a clause about limited slip differentials (they are also self-locking) - their properties are regulated separately by the manufacturer of the units. Such differentials require the presence of the frictional properties of the oil (to increase friction in the right place at the right moment), which means the appropriate additive. Such oils, as a rule, have in their name the letters LS (Limited slip - literally "limited slip").

In addition to the existing ones, there are still outdated API designations, namely:

• GL-1 - oil without antiwear additives, sometimes used in tractors. It is recommended to use MT-1 oils instead.
• GL-2 is a slightly better oil, copes with the protection of worm gears.
• GL-3 is an oil for transmissions operating under moderate to heavy duty or for spiral bevel axles operating under light to moderate loads. Not suitable for hypoid gears.
• GL-6 - This specification was developed for high offset gears. Contains more EP additive than GL-5. Now it is not used, because the manufacturers of aggregates are trying to make transmissions with smaller gear displacement angles without using outdated designs, and for them the GL-5 provides sufficient protection. In general, we were too smart with this GL-6 :).

In general, these oils differ in their antiwear and EP additives. The higher the number, the greater the percentage of content.

SAE J2360 Standard

There is another standard developed by the Society of Automotive Engineers (SAE) after it was discovered that the GL-5 and MT-1 did not meet all the requirements in modern transmissions. Made on the basis of these standards plus the American military standard MIL-PRF-2105E. For GL-5, added tests for the absence of sludge and abrasive deposits on the shafts (which can affect the seals), for compatibility with seal materials and for stability of properties during long-term storage. So, when choosing an oil, it will be useful to check the presence of this standard, in addition to the usual GL-4 and GL-5.

Standard GOST 17479.2-85

The Russian standard for transmission oils, introduced together with the engine standard in 1987, as well as for engine oils, contains a classification both in terms of viscosity and the level of performance properties. The designation has the following form - TM-5-18, where TM means "transmission oil", number 5 characterizes the level of performance properties, number 18 is responsible for the indicator of kinematic viscosity. In total, there are 5 gradations of properties from 1 to 5, by analogy with the API classification (i.e. TM-1 is equal to GL-1, and so on). Here is the API and SAE mapping table.

In addition to the GOST designation for oils produced in Russia, the designations adopted for transmission oils until 1987 are widespread. Up to being placed on the label as a name (for example, Tad-17i). Here is a table of correspondence between these names and GOST.

Oils for automatic transmissions

With oils for automatic transmissions, the situation is slightly different. There is no officially developed international standard for them. De facto, such a standard is General Motors specifications called Dexron (for example, Dexron II, Dexron III, and so on). The logic of assigning digital indices is simple - as the automatic transmission improved, another specification was issued for this box. In Russia, two specifications are most common:

• Dexron II (aka Dexron II D) is a mineral oil used in cars since 1981.
• Dexron III is usually a synthetic oil with improved thermal, antioxidant and frictional properties relative to Dexron IID. Used in cars since 1993.

In addition, there are less common, but also circulating specifications:

• Suffix A - Sometimes called Dexron I or TASA (Type A Suffix A). This is an early specification developed in 1957 with the US military.
• Dexron II E - improved low temperature fluidity relative to Dexron II D, however it is not recommended to use II D instead of II E.
• Dexron VI - approximately since 2006 this fluid replaces Dexron III and Dexron II E. First fill oil in GM vehicles. The low distribution is apparently due to the inertia of consumers' thinking and the postulate of "filling liquids according to the manual", in which this standard could not be spelled out on cars older than 2006.

Of course, in addition to those described, there are still a bunch of other classifications of transmission oils, such as ZF specifications (one of the largest manufacturers of all kinds of transmissions), many automakers have their own specifications, Ford's Mercon (by the way, compatible with the corresponding Dexrons) ... However, for the most part they are very close to ATFs from GM, and if we talk about manual transmissions, then compliance with API and SAE tolerances is mandatory for them. If you are interested in more details about automatic boxes, you can read about. It describes the types of boxes, liquids, compatibility and replacement.