Sometimes what seems like a final drive problem may be something else -- like the charge pump. 

---

Here are a few other Shop Talk Blog posts you might find helpful ...

• Repairing a Final Drive Motor
• Does Your Skid Steer Drive Motor Need Service?
• Reviewing Hydraulic Connections on a Final Drive

---

A weak charge pump can make it seem like you've got problems with your final drive motors. That means you could replace your drive motors and not see any change in their performance. And to complicate things further, a weak charge pump that is ignored can lead to irreparable damage to your brake assembly. So what is a charge pump and how does it affect your final drives?

What Are Charge Pumps?

Charge pumps are hydraulic gear pumps that can serve several different purposes in a hydraulic system:

• Supplying hydraulic fluid flow and pressure to make up for internal leakage and losses within pumps and motors
• Providing additional flow and pressure needed to keep components within motors and pumps lubricated with hydraulic fluid
• Providing flow and pressure for auxiliary functions, including braking systems for final drive motors

When charge pumps affect final drive motors, it's usually involves the brake systems.

Charge Pumps and Final Drive Brakes

When the charge pump starts to go out, it won't have enough pressure and force to release the brakes on your drive motors. In the beginning, the brake disc pack will be the first component to be damaged. If ignored, the final drive brake assembly can be seriously damaged leading to costly repairs. Eventually, the final drive motor itself can be affected and suffer damage.

Symptoms of Charge Pump Issues

Symptoms of charge pump issues typically include ...

• Resistance to controls
• Brake drag
• Squealing or screeching drive motor
  
• A machine that will not move
• An overheating final drive

Of course, these symptoms can also be related to other issues (e.g., a leaking brake seal, worn out bearings). However, before sending your final drive motor in for repairs, its a good idea to check out the condition of the charge pump.

Checking the Charge Pump Pressure

If you don't have a service manual for your machine, find a copy or borrow one. Go to the section that talks about pump/charge pump  -- it may be under hydraulic charge pump pressure. This section will have the information on how to check the pressure. And it well tell you what the pressure readings should be if the charge pump is working correctly. Based on the results you get from testing, you can determine whether your problem is the charge pump or the final drive(s). Another quick test you can run is to check the pressure on both the brake lines. If they aren't the same, then the problem likely the charge pump.

Conclusion

Charge pumps can affect the performance of your final drives, and can even cause damage if they don't have the pressure and flow needed to release the brakes on your motors. If you have any questions about charge pumps and how to tell if they are the source of your problems, you can give us a call at 877-751-1854.

---