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How Aging Gear Oil Affects Final Drives

There's a reason why we encourage our customers to regularly replace the gear oil in their final drives. Gear oil is inevitably going to degrade, or age, over time. Find out what that means to your final drive motor.

How Aging Gear Oil Affects Final Drives

Here are a few other blog posts that might be of interest to you:

Why is Aging Gear Oil Important?

Let's look at the basic effects of aging on gear oil:

  • Increased thickness
  • Loss of lubrication
  • Reduced ability to conduct heat
  • Depletion of EP/AW additives

These four effects work are all going to lead to issues with premature wear. And some of them interact with each other to accelerate aging and its effects.

Increased Thickness

Over time, gear oil will thicken. In fact, one of the ways that our final drive technicians can tell that the gear oil hasn't been changed is by its viscosity. If we open up a final drive and it looks like pudding inside, we know it hasn't been maintained well. And that thickening will lead to a host of other problems.

Loss of Lubrication

As gear oil thickens, it simply can't do a good job of lubricating. The thickness slows its movement down can't respond as quickly to generate the protective film between contacting surfaces. That leads to an increase in friction, which is never good. Friction is always going to generate more heat and will also lead to premature wear. Premature wear will eventually introduce generated contamination which gives rise to even more friction. It is a very damaging cycle. 

Reduced Ability to Conduct Heat

As gear oil ages and thickens, it can't conduct heat away as effectively. In fact, if anything, it will trap heat inside your planetary hub -- and heat is one thing that will accelerate how fast gear oil ages and breaks down. Heat also increases friction, which is also going to generate more heat. 

Depletion of EP/AW Additives

Key additives, such as EP (Extreme Pressure) and/or AW (Anti-Wear), are going to start breaking down chemically. These additives are extremely important to the performance of your gear oil because they enable lubrication under extremely high forces and provide enhanced anti-wear properties.

Impact of Aging Gear Oil on Your Final Drive Motor

Gear oil is used in the planetary hub of your final drive. This is the portion that contains the planetary gear set that converts the speed generated by the hydraulic motor into the torque needed to move your machine. Wear in this part of your final drive will impact its performance and, as mentioned earlier, generate internal contamination that will accelerate wear. It will reduce the useful life of the components in the planetary hub -- and lead to expensive repairs or rebuilds. 

Minimizing the Effects of Aging

To minimize the impact of aging gear oil, there are two key things we recommend:


We even have a blog post detailing exactly how to do that.



As soon as one of our technicians opens up the gear hub, they can tell immediately if the owner has neglected to change the gear oil -- sometimes just from the sulfurous smell that emanates from it.  Failure to change out the gear oil can void our warranties. To keep your final drive at peak performance and extend the gear hub as long as you can, we encourage you to check and change the gear oil on a regular basis.

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Topics: Final Drive Maintenance, Gear oil, Planetary Hub

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