What Is The Importance Of Surface Conditions For Final Drive Components

The surface is the key thing that helps different components perform their functions within the final drive effectively. Good or fine finish surfaces meet the exact clearance needed for specific operation within the final drive.

Damage on the surfaces like pitting or scratching can adversely impact the performance of your final drive motor.

It will minimize the clearance and promote metal-to-metal contact, leading to premature failure of components. Therefore, you cannot underestimate the surface conditions of your final drive motor.

In this article, you will know more about the importance of surface conditions. Different types of surface damage and solutions for preventing surface damage. Sounds exciting? Let’s find out!

Introduction: Surface Conditions

Some components within the final drive require tight tolerances to meet or fulfill their operational needs efficiently and effectively. Surface conditions are the conditions that affect how friction works and how fast the object performs its function.

A good surface finish means a more dimensionally stable component. This means this component will not affect the performance of other components within the assembly. It will also contribute to the longer life of your final drive.

What Is The Importance Of Surface Conditions?

The reason why you should consider surface conditions lies in the relation of power and torque.

1.   Link Between Power and Torque

You can figure out the link between the two through the following formulae:

P = Power

T = Torque

𝟂 = Rotational Speed

This equation specifies that torque is proportional to power and inversely proportional to the rotational speed. This means as the power increases, the torque increases. Similarly, as the torque increases, the rotational speed decreases. If there is a loss in power, this means a loss in torque.

2.   Impact of Rough Surface on Fluids

The rough surface represents the uneven metal surface. When fluid flow over, it loses some energy because of unevenness.

The uneven surface results in more friction, leading to power loss. It needs to do great work flowing from one point to another. In the beginning, these losses are referred to as minimum, but as time passes, they result in severe damage.

3.   Fluid Escape

A rough surface forces the fluid to move in the sections where you don’t want it to be. The fluid has certain pressure move on in the area offering low resistance. The damaged surface results in this area.

Whenever the fluid takes the wrong path, you will experience a decrease in the total amount of torque. This path often results from the leaking seal in your final drive.

Kinds of Damaged Surfaces

There are several kinds of surface damage that you can experience in your final drive motor. The most common types of damage are as follows:


Abrasive contaminants are the main cause of scratches within the final drive. Whether they are within hydraulic fluid or in planetary portion within gear oil. The outside of the final drive leads to severe forms of abrasive contaminants.

Sometimes the internal components also result in contaminants. These contaminants are due to catastrophic failure or wear and tear inside the final drive motor. These damages form metallic particles.

Remember, you can experience rapid wear because of abrasive contaminants within lubricant or hydraulic fluid.

This happens when there is no optimum lubrication, or the lubricant expires. It is unable to perform its function. Scratches also result from excessive wear. For instance, see the above image.


Cavitation leads to pitting in your final drive motor. As the name reflects, they have the appearance of smaller pits. When these pits grow in size with time, you can witness the missing metal in large amounts—pitting damages the most important surfaces within the final drive. This leads to a reduction in fluid power as well as torque generation.

The pitting phenomenon occurs when minute bubbles form within the hydraulic fluid close to the metal surface and explode.

These minute bubbles explode highly and form pits over the entire metal surface. The exploded metal then gets mixed in the hydraulic fluid leading to contamination. You can witness pitting mostly on the cam ring or thrust plate.

Cavitation forms when there is water present within your hydraulic fluid. You can prevent this by preventing your hydraulic fluid from water and moisture.


Galling may occur when metal surfaces stick to each other during direct contact. This occurs when metal surfaces experience excessive load. It is similar to friction welding but on a very low level.

As sliding continues, the sticking ends up leaving behind a rough surface. A rough surface contributes to severe galling and higher friction.

Galling mainly occurs because of no lubricant or a low level of lubrication. The components which bear severe galling include bolts and bushings.


Fretting is a phenomenon that has a link with bearings. On the other hand, annoying has a link with two contacting metal surfaces. The main difference between these two phenomenon types is how they occur.

Fretting occurs because of oscillation or vibration, while galling occurs through mating and sliding. This phenomenon results in rough surfaces, higher friction levels, and worse contamination internally. Fretting has an appearance similar to fretting. You can reduce this phenomenon by keeping lubrication at an optimum level.


Cracking is what everyone wants to avoid in their final drive. Some people think tiny cracks cannot do much damage, but when they spread, they do so with the speed of sound. The major cause leading to cracking is high stress at one point.

The stress on a single point is so high compared to what it is in the surroundings. This is the main reason behind their spreading faster and unexpected failure.

The excessive load is the root cause of crack formation. You can make them worse if the component has premature failure effects.


From the above information, it is clear that damage to the surface mainly results from:

  • High loads
  • Abrasive contaminants in Gear Oil as well as Hydraulic Fluid
  • Selection of the wrong kind of gear oil
  • Cavitation
  • Wear and Tear

The surface damage is normally because of wear and tear, but you can eliminate this effect by applying the following measures:

  • Avoid contaminating your gear oil and hydraulic fluid
  • Maintain the oil level to the optimum
  • Avoid Excessive loading

Doing this will increase the effectiveness and efficiency of your final drive motor and the life of your final drive.

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