A customer sent in a Hy-Dash brand final drive in for repairs. The symptoms were quite simple: the tracks on one side of the machine had been losing power and finally refused to move, so he pulled the track drive and brought it to us. In this Shop Talk Blog post, we are going to look at what caused this kind of catastrophic failure and how you can avoid a similar fate.

Basic Inspection of the Hy-Dash Final Drive

The exterior of the Hy-Dash final drive motor was thoroughly cleaned before the drive itself was disassembled. Upon disassembly, we found no evidence of poor maintenance. Everything seemed to be in fair condition for the age and hours on the motor, and it showed no evidence of the usual causes of loss of power in a final drive or travel motor.

It seemed that all we could find was the usual wear and tear -- but nothing severe enough to affect the performance of the motor to the point it would stop turning. Finally, however, we discovered what had caused the gradual loss of power and eventual failure.

Source of Final Drive Motor Failure

While inspecting the lower shaft, coupling, and upper shaft, we realized that the gears on the shafts were not longer engaging with the coupling. No power or torque whatsoever was being transmitted at this point. When the coupling fails to grip the upper and lower shaft, the drive will not turn regardless of how much power you give to it.

Upon closer inspection of the lower shaft, it was obvious that the teeth had been worn away from the shaft and the same was true for the upper shaft.

Gearing Up for Problems

The image below clearly shows the difference between worn teeth and good teeth on a drive shaft.  Notice that as a shaft begins to wear the teeth develop a pointy shape.  The teeth should have a flat, thick surface on the tips for optimum performance and transmission of power and torque. The gradual loss of power would have developed as the gear teeth began to wear away. Once they were no longer able to engage the coupling, the travel motor would no longer turn. The problem was as simple as that.

Cause of Failure

This type of extreme wear on the main shafts is caused by going back and forth too rapidly on the toggles/joysticks.  It very similar to going into drive on your vehicle and then immediately putting it into reverse while skipping neutral.  You know that would be rough on your car … imagine what it can do to your final drive! 

Lesson Learned

Just because a machine is built to be tough and powerful does not mean that it can be abused without repercussions. If you want your machine to keep running at optimum power for as long as possible, avoid going back and forth too rapidly on the drive controls.  This can gradually reduce the useful life of parts and bring your machine to a halt, and result in something wrong with your final drive that can cost hundreds of dollars to repair.

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