Car is quite complicated mechanism, which consists of many components and mechanisms. During operational process, all its parts interact with each other. As a result, friction occurs. In time, the duration of such process can harm the components of one or another unit. To avoid this accident, different types of lubricating oils are used for mechanic vehicles. Transmission oil is referred to such lubricants. This oil is used for greasing of transmission and steering mechanisms. In this article we’ll describe its functions, types and what to pay attention to, while buying it.
1. Main characteristics and functions of transmission oil.
2. Gearbox oil types.
3. How to buy necessary oil?
1. Main characteristics and functions of transmission oil
Oil foe transmission is a special composition, which is used for protection of change gearbox components, drive axles baseband transmission, transfer gear, steering mechanisms and various types of
chain drives and geartrains (gear system).
Gearbox oils are made of base part synthetic or mineral substructions, enriched with various functional additives (anticorrosive, anti-wear-related, antiwelding). More often, such substance is got from oil-product remains with addition of different supplements, which include chloride, phosphorus, sulfur and bisulfide.
The operation principle of transmission oil is in creating of protective layer, which covers the components and protects them from threats and hard working conditions.
The consistence of this oil must be viscous enough and don’t allow layer destruction under impact of high temperatures and shock stress. Besides, under normal condition, its thickness doesn’t have to interfere with work of mechanism in cold season. In other words, it must not depend on temperature difference. This characteristic of transmission oil is called the viscosity index.
Main requirement to gearbox oils are determined after working material analysis, gearbox working conditions and purpose of oil itself. Considering transmission heavy loads, the main requirement for gearbox oil is resistance of speed skidding rate, considerable temperature difference (from -60 to +150°С) and high pressure.
Mafunctions of transmission oil are:
- reduction of power loss during friction;
- heat elimination from mating surface;
- protection from wear out, wedging-in, pitting corrosion;
- reduce of noise and vibration from timing gears;
- non-waste and nontoxicity;
- shock stress reduction.
For durable and reliable fulfilling of its functions, the oil must have following characteristics:
- low level of foam formation;
- ani-wear-related and antiwelding properties;
- high resistance to oxidation processes;
- high visco-temperature threshold;
- protective properties during water contact;
- optimum level of transmission process rubber elements interworking;
- stability of composition chemical reaction during whole shelf-life.
2. Gearbox oil types.
Various agents, additives, which compose all transmission fluids, have a large impact on gearbox oil viscosity. The most renown transmission liquid is petroleum oil, which has positive features and low cost. Petroleum oils became basis for making synthetic transmission oils, quality of which surpassed the one of their predecessor. It was possible due to composition, which could coact with any additive and supplement. Therefore, working lifespan of components is largely increased with using of this type of transmission oil.
Though, complication of producing and perfect quality affected the cost of synthetic gearbox oil, which made it expensive. If you have no wish to pay much money and you always look for middle ground, then you should pay attention to semi-synthetic oil, which is perfect combination of quality and cost.
As engine oils, the transmission ones are also divided into types depending on viscosity rate. There are such conventional types (SAE classification):
winter type - SAE 70W, 75W, 80W, 85W;
summer type - SAE 80, 85, 90, 140, 250.
The convention of such dividing is determined by constructional peculiarities of transmission packs produced by different manufacturers. For example, depending on different loads and oil operating temperature, there are some transmissions, for which winter compositions can provide sufficient level of protection at wide range of ambient temperatures (these are mechanical transmissions installed in motor-cars).
Due to last changes of standard viscosity classification, all types of oils must be marked: W (f. e. SAE 75W) for one rate of winter, one rate of summer type (f. e. SAE 85) or combination of these rates (SAE 75W-85). Marking of two winter rates will no longer be used (f. e. markings acceptable before SAE 75W-85W, SAE 75W-80W, SAE 80W-85W).
New marking standards and additional viscosity rate require from oil vendors exact estimation of oil characteristics level. Due to this, recommendations of manufacturers become more specific. For example:
oil type SAE 80 – is meant for summer use;
SAE 80W – is meant for winter use;
SAE80W-80 – all-season option.
Now transmission and engine oils, which have the same viscosity, according to SAE marking, will be substantially different.
As for unified system for oil classifying by any definition (quality, purpose and performance characteristics) – it does not exist. And internationally recognized system is API includes only oils meant for mechanical transmissions. According to API, all oils are marked as API GL and are divided into 5 quality groups: from API GL-1 to API GL-5 and few project-oriented. Main features of this classification system are transmission working conditions and its construction. To auxiliary characteristics refer presence of antiwelding and antiwear supplements.
In European countries also used classification ZF TE-ML, which includes all oils, including hydromechanical transmission liquids. Zahnradfabrik Friedrichshafen (or ZF) is one of the largest European companies, which produces power packs and transmissions. It created classification for all vehicle transmissions. According to it, any of them has its own lubricating oil list, and are marked from ZF TE-ML 01 to ZF TE-ML 14. All viscosity rates, types, quality degrees, trademarks and manufacturers are stated there.
Usually, recommended type of transmission liquid is stated in vehicle technological documents and is carved on transmission oil gauge. For most modern vehicles with robotic transmission used liquid type Dexron, Dexron-2 or Dexron-3. Though, recently new type appeared – type T or T2. It is not recommended to mix these two types. That’s why there are two colors for them: red for Dexron and yellow for T.
How to buy necessary oil?
Everyone understands that their cars can’t do without lubricating fluid. And it must be replaced quite often. The frequency of this process depends on composition mark and working conditions. For example, one type of oil must be replaced each 15000 km, another can last only 30 km. That’s why you should take selection of oil seriously. Buying the lubricant you should take into account: loading power, which affects component and relative slip speed. According to these values, you can pick up oil of certain viscosity and necessary number of antiwelding supplements.
Always read the information on label carefully. This will tell you whether you should or shouldn’t buy this product. Besides, buying petroleum, synthetic or part synthetic transmission oil, inquire its viscosity (stated on label). If the heating index (up to 100°С) will be less, than 24 mm2/s (class “140”), then it is good for cars in countries with warm climate. In cold climate it is better to use oil class “90”.
Also don’t forget the quality, because everyone knows that quality oil will give you necessary result and increase vehicle working lifespan. Of course, you can’t find out oil efficiency beforehand, but you can try oils produced by renowned manufacturers, whose production quality was proofed more than once.