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Truck Encyclopedia (32): Why does gear oil stick like paste?
Gear oil, commonly known as tail tooth oil, is different from engine oil, which is only responsible for the protection and lubrication between gears. However, as the end link of power output, after the power passes through the transmission, the output torque is large and the gear load is heavy. Therefore, the drive axle gear needs to be changed regularly and the gear oil is maintained.
● It is a head-to-head "lifting bar"
Before introducing gear oil, let's briefly understand how the drive axle works. The truck transmission converts power from the engine and transmits power to the drive axle through the drive shaft, which is converted through the gears (speed ratio) inside the drive axle, and finally transmitted to the wheels after passing through the differential gears.
Although the structure of the drive axle gear is relatively simple, the pressure on this set of gears is also very high when the truck pulls the cargo. As can be seen from the above GIF, the gears are all hard contact, but if the oil film is broken, the gear loses lubrication and heat dissipation, and the direct contact between the teeth can easily cause gear ablation, tooth surface damage (plastic deformation) and other failures.
The direct consequence is that your vehicle's drive axle squeaks, shakes, or even fails to drive. Think about the car you pulled, the car broke down and couldn't drive, how anxious you were.
Therefore, in order to protect the gears, improve transmission efficiency, reduce power loss, and prevent the protection of the gears inside the drive axle, it is necessary to change the gear oil regularly to lubricate and dissipate heat.
In order to avoid tooth surface wear and plastic deformation, the working conditions of drive axle gears require gear oil to have high viscosity and oil film strength, so gear oil usually contains more extreme pressure anti-wear agent. For an explanation of extreme pressure anti-wear agents, you can watch the previous article "Truck Encyclopedia: Good Oil Performance, All Dependent on Additives". This is one of the reasons why gear oil has such a high viscosity.
In addition, although the working temperature of gear oil is lower than that of engine oil, there is no independent radiator, and the temperature depends on the ambient temperature and the load condition of the truck. Secondly, except for a few high-end trucks such as Scania and MAN, the gear oil in the drive axle of most trucks generally does not have a circulation device and a filtration device, and the working state is soaking lubrication.
Therefore, gear oil must also have good high temperature resistance, oxidation resistance, foaming resistance, emulsification and rust resistance.
● Gear oil, also divided into grades
The American Petroleum Institute API has classified the performance of vehicle gear oils. There are currently 5 grades of gear oil. The specific performance is shown below.
● Editor's postscript
As a sophisticated transportation system, trucks have a bucket effect, and the absence of any shortcomings will cause vehicle performance to deteriorate or even lie down. Although the drive axle looks strong and durable, many card friends neglect maintenance, and the gears inside many drive axles are not in good condition.
When cardholders buy a car, the car will come with a vehicle instruction manual, which stipulates in detail the maintenance cycle of the drive axle and the requirements of oil, so when maintaining, cardholders should maintain the vehicle drive according to the requirements of the vehicle instruction manual.
It is important to make money and save money, but 7 points for car maintenance, 3 points for car repair, and maintenance on time to reduce wear and tear, so that the road to making money can be smoother.
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