A heavy-duty forestry machine with individual planetary final drives at each wheel experiences a grinding noise and excessive backlash when power is applied to one particular wheel. The noise is more pronounced when reversing. What is the most probable cause?

Question: A heavy-duty forestry machine with individual planetary final drives at each wheel experiences a grinding noise and excessive backlash when power is applied to one particular wheel. The noise is more pronounced when reversing. What is the most probable cause?

Answer options: ✅ Worn or chipped planetary gears within that final drive.

• A cracked rim or loose wheel nuts.
• A faulty hydraulic motor supplying the final drive.
• Incorrect tire pressure on the affected wheel.

Correct answer: Worn or chipped planetary gears within that final drive.

Explanation: Grinding noise and excessive backlash, especially pronounced under load and reversing, are characteristic symptoms of worn or chipped planetary gears within the final drive unit. This indicates internal mechanical damage. Cracked rims or loose wheel nuts would cause vibration or wobble but not internal grinding. A faulty hydraulic motor would affect power delivery, and incorrect tire pressure would only influence ride quality or grip, not mechanical grinding.