Transmission lubricants are used in gearboxes, transfer cases, axles and steering gears. There are many cars where the same engine oil is poured into gearboxes . But in individual mechanisms that are subjected to particularly heavy and complex loads, and where it is difficult to get oil droplets and fog from it, a transmission oil pressure supply is required.
Different groups and types of motor fluid are divided. The classification of gear oil also varies.
Accepted Classifications
One of the international classifications is the separation by viscosity. This classification of gear oils is called SAE. In it, lubricants are divided into seven classes, four of which are winter (denoted by the letter W), and the remaining three are summer. All-weather marking involves a double designation, for example, 80W90, 75W140 and others.
Another classification of gear oil, called API, involves the division into six groups. They are used depending on the purpose, because of which their type of gear transmission, specific loads and temperature are provided.
SAE gear oil classification in general
This classification was developed by the American Society of Engineers. She became widely known. Many motorists know her better than any other.
The viscosity grade of the lubricating fluid is found in the operating instructions of each vehicle.
The choice of what this classification of gear oils offers is based on the temperature indicators of the environment where the car will be operated. Viscosity properties are determined in relation to the achievement of 150 thousand SR according to Brookfield. If this value is exceeded, the bearings of the pinion shaft will begin the process of destruction. To avoid this, you should strictly follow the recommendations for low temperature data, choosing the right lubricant.
If the car is planned to be operated at a temperature of minus thirty degrees and below, then hydrocracking or synthetic lubricants, as well as semi-synthetic viscosity 75W-XX with a viscosity limit of 5000 cP, will be suitable for manual transmissions.
High temperature is determined at 100 degrees. Upon reaching it, the parts should not begin to collapse, even if you have to be under such influence for 20 hours or more.
Viscosity Classification of Transmission Oils: Details
Here, as well as in motor ones, lubricating fluids are divided according to a seasonal basis:
- winter - 70W, 75W, 80W, 85W;
- summer - 80, 85, 90, 140, 250.
In this classification, such a division is conditional, since different manufacturers have their own developmental features.
But the SAE J306 standard, for example, has such requirements that transmission fluids must meet. So, they should contain a single degree of winter or summer series, or a combination of both degrees. Two winter degrees cannot be at once.
In addition, if motor greases are designated in the range from 0 to 60, then gear lubricants range from 70 to 250.
So the developers tried to prevent possible errors when choosing oil. Thus, if motor and transmission fluids have the same viscosity, then according to SAE their values will be different.
API in general
The universal classification of gear oils for all types, alas, has not yet been created. But according to the API class for manual gearboxes, it is most convenient to classify lubricants.
On it, cars use GL-4 or GL-5 group oils. GL-4 is suitable for mechanics and gears with hypoid or spiral-conical pairs and is used in moderate climatic conditions. And GL-5, in addition to moderate, can be used in harsh conditions on different types of gears.
Separate API Groups
Let us consider in more detail all the groups that the API gear oil classification represents.
Group GL-1 owns mineral lubricants. These oils lack additives other than those that have antioxidant and antifoam properties.
GL-2 includes oils with anti-friction additives, which are used for worm gears with low rotating speed.
GL-3 is a lubricant that already has a considerable amount of additives, which include, and have wear-resistant properties. They are used in gearboxes with several stages and for steering, in main and hypoid gears. Spiral bevel gear pairs are used with oil, designed for operation at low speeds and not in harsh conditions.
The GL-4 group has a high percentage of additive content. These include those that have anti-seize properties. They are mainly used in cars with conventional gearboxes. The lubricant is able to function properly in such gearboxes, where there are high-speed rotation and low torque or vice versa.
GL-5 includes lubricating fluids that can operate in difficult conditions, where it is necessary to exert a lot of effort and overcome heavy loads. Such oils are used on different models of cars and motorcycles. Applicable for hypoid gears, pairs of gears working with impacts. Lubricants contain a large number of additives based on sulfur-phosphorus elements and reduce the likelihood of metallic burrs.
GL-6 oils provide good performance even under harsh operating conditions. They effectively withstand rotational speed, high torques and shock loads. They have the greatest number of anti-seize additives compared to other groups. But oils of this group are not used often.
The main number of gear oils is made on a mineral basis. Synthetics are used very rarely.
Other classifications
The classification of gear oil according to CAE and API is the most common. But there are other divisions. For example, lubricants for automatic transmissions belong to a separate category. They are not covered by the API as a gear oil classification. Zeke, Total, Mobil and other manufacturers are guided by their own indicators in the manufacture of lubricating fluids.
ATF classification
Oils for automatic machines are often painted in a bright color so that the motorist does not confuse and does not fill it in the manual transmission. Also, mixing colored liquids is not allowed,
There are no classifications for automatic transmissions that would be as unified as for manual transmissions. Therefore, this issue is addressed by the manufacturers themselves. So, in General Motors use the classification of Dexron, and in Ford - Mercon.
ZF classification
The classification of the company Zahnradfabrik Friedrichshafen, shortly ZF, is widely known. It is a leader among European manufacturers of gearboxes and engine systems. Having developed its own classification, the company offers to focus on their classes in terms of quality and viscosity.
Each gearbox has its own oil. The division provides both a letter code and a digital one.
What to base on when choosing
Classification of gear oils by API, SAE, etc., makes selection much easier. But, acquiring a lubricating fluid, one should also understand what tasks it should solve. Among them stand out:
- preventing too much friction and increased wear on the surfaces of gears or other transmission components;
- the energy expended due to the creation of the film must be reduced;
- creating heat dissipation;
- stopping or minimizing the oxidation process;
- the absence of a negative effect on the reaction of transmission parts on the surface;
- non-reaction with water;
- preservation of initial properties during long-term storage;
- reduction of noise and vibration arising from transmission work;
- non-emission of toxic fumes when heated.
Properly selected gear oil will successfully solve its problems and help to extend the life of the mechanisms.