The main physical and chemical properties of vehicle gear oil are basically the same as that of engine oil, as well as apparent viscosity, groove point, mechanical impurity injection, storage stability, thermal oxidation stability, etc.

The automobile transmission mechanism is the power transmission device between the engine and the automobile driving wheel, that is, the device that transmits the power generated by the engine to the driving wheel through the clutch, gearbox, transmission shaft, main reducer, differential and half shaft

The load on the gear is large, and the pressure on the lubricating oil film is also large:

In the general automotive transmission gear oil pressure up to 2000~3000MPa; The pressure of the gear oil on the hyperbolic gear can reach 3000~4000MPa; When driving on uneven roads, the impact and vibration caused by severe bumps will make the gear bear more pressure, so the lubricating oil between the friction surface is easy to extrusion and cause wear.

The operating temperature is lower than that of engine oil, but the range of variation is large:

Generally, the working temperature of automotive gear oil is not as high as that of internal combustion engine oil, even if it works under harsh conditions, the maximum temperature for a short time is only 100 ° C. Due to the high speed of foreign advanced cars, the sliding speed between the tooth surfaces is large, and the tooth shape is curved and the pressure is strong, so the oil temperature of the rear axle hyperbolic gear can reach 160~180℃. Because the working temperature of the rear axle main speed reduction gear box is the highest in the transmission device, the rear axle gear oil temperature is mainly considered when evaluating the vehicle gear oil. Because the gear used under harsh conditions, especially the hyperbolic gear, will be very high temperature due to friction, so that the lubricating oil adsorption film produces desorption and loses its function, forming direct contact with the friction surface of the metal, in order to prevent the wear and tear of the metal under extreme pressure conditions, in the gear oil to add extreme pressure anti-wear agent. The working temperature of the gear oil changes with the regular environment and seasonal changes, so the working temperature range of the gear oil changes greatly, and the gear oil with good low-temperature flow performance should be used in the cold region in winter.

The gear pair is in a state of boundary lubrication

Due to the high contact stress of the gear friction pair, elastic deformation occurs when the gear surface is in contact, so that the gear pair is in the state of elastic fluid dynamic lubrication, but because of the large speed change and the number of rotation times in the operation of the car, the gear oil is easy to be squeezed out from the teeth. Therefore, the vehicle gear oil is required to have good oiliness and extreme pressure. Extreme pressure gear oil has accounted for the vast majority of automotive gear oil used abroad. Other requirements for the quality of automotive gear oil should have appropriate viscosity, good viscosity-temperature characteristics, good thermal oxidation resistance and so on.