Causes Of Internal Leakage In Final Drive And Consequences

A final drive is an essential component of construction equipment. It transmits power from the engine to the wheels and is responsible for its overall performance. However, internal leakage in a final drive can lead to several consequences. These consequences include decreased efficiency, reduced equipment lifespan, and even accidents.

In this blog post, we will explore the causes of internal leakage in a final drive and its consequences. Stay tuned!

Introduction to Internal Leakage in Final Drive

The word “leak” / sometimes refers to “leakage” when used to describe a final drive motor. It immediately brings images of something being wrong with your vehicle.

Internal leakage has some benefits when you have an engine with a hydraulic system. But this is good up until a certain level.

Leaks are an inevitable part of any vehicle. The most common vehicle leakage is hydraulic fluid from the final drive motor. However, there’s more than one type of leakage exist that can occur.

What Do You Mean By Internal Leakage?

Internal leakage occurs when there is interference between different hydraulic system components. This could be because of an improper fit or less clearance. Let’s begin our discussion with Final Drive Motors.

The final drive motors are precision-built with the right clearances to operate effectively.

Clearance is the space between two surfaces in a machine. The clearance spaces between different components in an engine are crucial to proper function. For example, in an axial piston motor, the clearance is present in the center of the cylinder block and the piston.

This clearance offers proper lubrication to the piston cylinder and opening within. Operation requires a certain level of internal leakage for proper functioning.

The hydraulic fluid that flows through this clearance never leaks out of the system. From there, the hydraulic fluid is directed towards the reservoir through a drain line with low pressure. This result in zero fluid loss.

In other words, Internal leakage does not affect how well your final drive motor works.

Difference Between Good and Bad Leaks

While there are many reasons for internal leakage to exist. This could be because of cleaning or cooling systems.

Regardless of how you use your system, the hydraulic fluid never gets out of the system. Rather it is always directed from higher pressure area to lower pressure area.

Eventually, as time goes on and you keep using your machine. It results in wear from natural sources and dirty fluids, leading the operating clearance to grow.

When the clearance grows enough, it will lose more fluid internally. Keep in mind that leakage that takes place internally never contributes to engine performance.

You can’t afford to let your hydraulic system suffer. As more fluid gets lost internally, the efficiency will decrease and performance may become less than expected!

If the operational clearance grows more than the optimum limit, it will lead to fluid bypass. When this happens, you cannot accomplish any work at hand with your final drive and pump.

What Leads to Excessive Leakage Internally?

Several causes lead to excessive leakage internally. Some of the major causes are as follows:

  • Wrong Choice of Replacement Components
  • High Temperature During Operation
  • Wrong Hydraulic Fluid Usage
  • Damaged Seals

1.    Wrong Choice of Replacement Components

The wrong choice of replacement components can lead to excessive internal leakage. This is because of the low quality of gear assembly, poor gear design, and poor mounting.

It results from insufficient or incorrect knowledge about the available options for an individual component.

Sometimes you also get a component that offers low operational clearance and is not a perfect fit. This is also one of the reasons for excessive internal leakage.

2.    High Temperature During Operation

High temperature during operation increases final drive motor temperature under load.

Excessive internal leakage increases the internal friction and requires extra lubrication to ensure transmission efficiency.

As the temperature due to increased friction increases, the hydraulic fluid becomes less dense. This Reduction in viscosity due to high temperatures contributes to Excessive Internal Leakage.

3.    Usage of Wrong Hydraulic Fluid

Using the wrong type or brand of hydraulic fluid can lead to excessive internal leakage. It causes wear and tears in your final drive.

The reason is the wrong viscosity and fluid density level. Wear and tear inside the final rive contaminates the hydraulic fluid. These contaminants, along with fluid, remain inside and cause deposition. This causes further wear and tear.

4.    Damaged Seals/ O-rings (Caused by Internal Leakage)

Damaged seals are the most common cause of internal leakage in Final Drive Motors.

These seals are not seen at first, but they become evident once the oil gets contaminated with dust, water drops, or dirt.

Damage can occur in different ways, such as:

  • Hardening of the seal material due to metalized oil and insufficient lubricant
  • Poor quality seal edges due to manufacturing defects or incorrect assembly
  • Faulty sealing surfaces due to mechanical damage

Consequences of Extra Internal Leakage

Usually, a final drive will show some signs of weakness when it got severely affected by excessive internal leakage. When it is weak, you may experience the following consequences:

1.    Pull on One Side

Suppose you’re noticing that your machine is pulling significantly to one side. It could be an indication of a final drive motor. Your one final drive is badly affected because of excessive internal leakage.

2.    Difficulty While Moving on Slopes

Suppose your final drive motors on excavators face the same issue of excessive internal leakage. This will make your excavator unable to climb on the hill or sloppy areas.


If you experience nothing in the issues mentioned above in your final drive motor. This means the only cause of internal leakage might be worn-out final drive parts. When a surface has worn out and lost its finish, it’s possible to rebuild the underlying material to maintain an OEM tolerance.

If you’re tired of the headaches and money spent on internal leakage in final drives and repairs, see Xugong Final Drive Parts. Xugong parts are your go-to choice when it comes to affordability and reliability. We’re the go-to shop for all your final drive motor needs. From rebuilds and repairs to buying new or remanufactured final drives – Xugong parts have you covered!

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