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Revisiting the Topic of Gear Oil

Gear oil is an important piece of the puzzle when it comes to making your final drive motor last. In this Shop Talk Blog post, we are going to talk about gear oil for final drives.

Revisiting the Topic of Gear Oil

Gear Oil and Final Drive Motors

Gear oil serves several purposes:

  • Reduces friction through lubrication
  • Conducts heat away from critical components
  • Reduces wear
  • Prevents corrosion

All of this helps to increase the useful life of your final drive motor. With final drive gear hubs, it is important that you use the right kind of gear oil because of the aggressive environment inside that hub: extreme pressure, heat, shock loads, and more all make it a challenge for a good gear oil to do its job.


Gear Oil versus Engine Oil

Gear oil is not the same as engine oil -- for one thing, it will have a higher viscosity than engine oil. High viscosity oils provide a thicker fluid film for protecting surfaces and provide better wear resistance than less viscous oils. However, lower viscosity oils are better are removing heat and result in reduced friction -- but they cannot handle the high pressures that occur as gear teeth interact with each other in a gear hub. Most gear oils have additional additives to help with these high pressure environments, and that additive usually involves sulfur. Sulfur can damage bronze and brass bushings, so gear oil can’t be used just anywhere.

SAE Gear Oil Designations

One of the most common gear oil designations would be the SAE designations. With SAE gear oil grades, the higher the designation number, the higher the number the more viscous (or thick) the gear oil is going to be. Just keep in mind that the SAE gear oil viscosity numbers are not a direct comparison to SAE engine oil viscosity measures (e.g., the engine oil equivalent to 80W gear oil is not going to have an 80W designation).

Multi-Grade Gear Oil

The gear oil recommended for use in just about all final drive motors is a multigrade gear oil. That means that it contains additives that change its viscosity at different temperatures. Multi-grade gear oils are represented by two numbers.


 The single-digit designation with a W represents the performance of the gear oil at lower temperatures (some people associate W with winter). This represents the low-temperature behavior of the gear oil and was tested at 0°F. It can be thought of as its cold crank viscosity.

The number without a letter beside it represents its performance when hot, with its viscosity measured according to SAE guidelines at a temperature of 212°F. This can be thought of as its actual working viscosity.


Gear Oil Recommended for Final Drives

For most final drive motors, we recommend SAE 80W/90 gear oil. It is designed to handle the high pressures and wear that gear hubs are exposed to, and works quite well for final drive gear hubs. However, we encourage you to find out exactly what your final drive manufacturer recommends and use that.

Texas Final Drive is your partner in providing new or remanufactured final drive hydraulic motors from a single mini-excavator to a fleet of heavy equipment. Call today so we can find the right final drive or hydraulic component for you, or check out our online store to find your O.E.M. manufacturer brand motor now.

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Topics: Final Drive Motor Gears, Final drive motor, Gear oil, Lubrication

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