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Why the Viscosity of the Gear Oil is Critical for Final Drive Motor Performance

It is always advisable to change your gear oil regularly to ensure that the final drive motor runs efficiently. This is especially true for heavy-duty diesel engines such as the ones found in excavators. Even though not all excavators can be considered to be big since their net rated power can range from 14.5 horsepower to 512 horsepower.

One important property of the fluid that is maintained when you change your oil regularly is viscosity. We’ll look at how viscosity impacts the efficiency of the gear oil, and what the specifications mean for Bobcat, Komatsu, or John Deere final drive motors.

Enhances Efficiency

The gear oil needs to be viscous enough to prevent friction between metal surfaces under high levels of pressure. Viscosity refers to the thickness of a fluid, which is in centistokes. Honey is thick and has a value of 10,000 centistokes, as opposed to 1 for water.

Gear oil has a viscosity of about 8,200 centistokes, which is much higher than hydraulic fluid. With a viscosity ranging from 16 to 100 centistokes, hydraulic fluid does not have the thickness to provide the need protection for the moving parts in the drive motor.

Therefore, if the viscosity of the fluid is compromised significantly, the final run motor cannot perform at its peak. One common culprit that causes premature failure for 90% of Bobcat machines, is a clogged case drain filter.

When the filter is clogged, the pressure rises and the seal breaks. The hydraulic fluid finds its way into the gear section. The resulting viscosity is too low to provide the required protection for moving parts. As the gear oil loses its thickness, critical components begin to break down. Eventually, the drive motor fails.

Effect of Temperature

The viscosity of the fluid can be affected by temperature. At high temperatures, it flows with ease. It is advisable to run the engine for a couple of minutes, before changing the gear oil of your final drive motor.

Manufactures of final drive motors provide specifications for gear oil viscosity, among other specs in the manual. However, people are sometimes confused by the grading in the specifications. For example, if you look at your John Deere’ manual, the viscosity grade is probably going to be 10W-30 for its gasoline engines.

“W” stands for Winter Standard Grade. This means the fluid was tested in low temperatures. If the engine oil specifications for your John Deere is listed as 10W-30, the first number indicates the value for the Winter Standard Grade is 10. The second part denotes the value is 30 for the Standard Grade.

When the viscosity of the gear oil in your excavator final drive is compromised, its lifespan is significantly reduced. You need to change your gear oil regularly to ensure the fluid is working in its tip-top performance. The gear oil needs to have specific chemical and mechanical properties so that it can remain efficient even when subjected to significant amounts of pressure and heat.

In Conclusion

You need to pay close attention to the specifications by given by John Deere and other excavator drive motor manufactures. If you need to consult a grading chart, note that the tables are different from those given for regular automotive oils. If you keep these things in mind, you can ensure you get the finest gear oil that will always uphold the performance of your excavator.

Our family at Mini Final Drives has been providing excellent Quality, Value, and Service for over 50 years, and you can continue to count on us for a lifetime of friendly, helpful support for all your final drive and travel motor needs. Call us today at 877-483-2806 or visit our online store at to find and order what you need today for Fast and Free delivery to your door.

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