October 5, 2017
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Eliminating External Causes for Final Drive Failure

There are times when what we think is a problem with the final drive actually has another cause.  If this is the case, then it only makes sense that replacing the final won’t fix the problem and may result in damage to the replacement.  In this week’s Shop Talk Blog post, we are going to look at what might be wrong besides the final drive.

Charge Pump

A common problem that many people mistake fora weak final drive is a malfunctioning charge pump. If you notice the final drive is acting weak and is making a screeching noise, the problem is probably the charge pumpA weak charge pump cannot provide enough pressure to disengage the internal brake on the final drive motor. This is similar to of driving a car with the emergency brake on.  While this problem is not in the final drive itself, failure to address it will eventually result in severe damage to the final drive motor.


Track Tightness

If you have a tracked machine — whether its a CTL, MTL, mini-excavator, or full-size excavator — your tracks will affect the performance of your final drive motor. If the tracks are too tight or the tracks and their components aren’t in good condition, the increased friction can cause your final drive motor to seem weak. Check the tightness and condition of your tracks before you conclude that the problem is with the final drive.

High Speed Mode

If you machine is having trouble climbing steep grades or keeps trying to steer to one side, there is a good chance your final drive may be trapped in high-speed mode. High-speed mode means more speed and less torque. If your final drive motor is stuck in high-speed mode, it may not be able to generate sufficient torque. This would be a problem with the speed control system and not with the final drive itself.


Back Pressure in Case Drain

The case drain line is designed to be a low pressure line, but it can become pressurized when there is a blockage. If your final drive motor has a case drain line, trace the line until you find the case drain filter. Remove the case drain filter and check to see whether it is clogged or blocked. If in doubt, replace the filter and determine if there is improvement in the performance of your hydraulic motor. Always follow the manufacturer’s recommendation for checking the case drain filters. You will save thousands of dollars in unnecessary repairs and avoid some truly catastrophic damage to your final drive motor.

Pressure and Flow

A lack of hydraulic pressure and flow is one of the most common causes behind a weak final drive or travel motor, and it is not the fault of the motor.  You can eliminate this as a possibility by checking the pressure on the final drive and referring to manufacturer guidelines to determine what the reading should beA lack of pressure could be caused by a hydraulic fluid leak, insufficient fluid in the hydraulic tank, or something similar.

A Warning

Replacing a final drive without making sure that it’s actually causing the problem will only mean more downtime and the potential for irreparable damage to the new final drive. Always address external causes before installing a new, reman, or rebuilt final drive motor. If you aren’t sure whether it’s the drive or not, describe the symptoms to an expert and get a second opinion.  Remember you can always call us at Final Drive Parts at 888-934-6257!

Additional Blog Posts

Here are some other Shop Talk Blog posts that you may find helpful …

Charge Pump Failures on CTLs and SSLs

Why Is My Final Drive Motor Weak?

Flushing the Hydraulic System


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