A little bit of periodic maintenance can reduce the downtime for your mini excavator and extend the service life of its final drive motor. It’s an obvious, yet often overlooked activity—checking and changing the gear oil in your heavy equipment’s final drive.
Final Drive Maintenance Basics
Let’s begin with some maintenance basics. Ask yourself these questions:
- Do you have a documented maintenance schedule for each piece of heavy equipment?
- Do you know when this equipment last received a change of final drive gear oil?
- When was the last time the oil levels were checked in the travel motors?
If you can provide definitive answers, then you clearly understand the importance of gearboxes and lubrication. An uncertain answer means your equipment may need more maintenance attention.
To begin with, always check the owner’s manual for the factory-recommended oil change schedule. A useful guideline is to check the oil level for every 100 hours of operation and do an oil change at least once a year or 200-300 hours, whichever comes first.
Final Drive Maintenance: Checking The Oil Level
Mini excavator final drive gearboxes are designed to be filled only halfway, or to the center of the cover plate where the oil service plugs are located, hence the need to position one of the plugs at the 3 o'clock or 9 o'clock position if there is not a plug located in the very center of the cover plate. Filling to this halfway point ensures adequate lubrication. Never fill beyond the center of the cover plate, as this can create excessive pressure, damaging seals and even fracturing or dislodging the cover plate!
Now, let’s review in detail how to check a final drive’s oil level.
First, make sure that the equipment is on level ground. Locate the cover plate of the final drive motor and identify two or three drain plugs. Next, position the travel motor so that one plug is set at 12 o’clock and another plug is positioned at either 3 or 9 o’clock.
Ensure that the plugs and the adjacent areas are clean and free of dirt, sand, and other debris. Keep in mind that the plugs may be under extreme pressure. You may need a few hammer strikes to loosen the plugs.
Next, carefully and slowly turn your wrench to loosen the plug at the 3 o’clock or 9 o’clock position. Allow any pressure to escape gradually. Caution is warranted here, as extreme pressure can turn the plug into a projectile.
With the plug removed, a small amount of oil draining out means the oil level is fine. A large amount can mean that the drive was overfilled (not a good thing) or that the equipment is not level.
If the oil level is low, open the plug at the 12 o’clock position and add oil through this hole until you see oil begin to drain out of the 3 o’clock or 9 o’clock opening. Be sure to use the correct type of oil and never mix oil types.
Tightly secure the loose plugs, and your equipment will be ready for its next job.
Final Drive Maintenance: Changing the Gear Oil
Changing the gear oil or gear lube is equally a simple and straightforward process.
Start by checking the owner’s manual to verify the oil type – remember that you should NEVER combine different types or grades of oil.
Due to the oil’s viscosity (thickness), draining the oil will be easier when it’s warm.
Our instructions here will assume that you are changing the oil as a separate task from checking the oil level. Some steps may appear to be similar.
Make sure that the equipment is on level ground. Next, locate the cover plate of the final drive motor and identify two or three drain plugs. Position the travel motor so that one plug is set at 6 o’clock, and another plug is set at either 3 or 9 o’clock.
Be sure to clean the drain plugs and the adjacent areas from any dirt or debris that may be present. Again, being cautious of potential pressure hazards, gradually loosen the 6 o’clock-position plug.
Be sure to place a basin or pan underneath this plug to capture the oil as it drains. Also, you can loosen the plug at 3 or 9 o’clock to help vent the oil. Remember, a few hammer strikes can help you loosen stubborn plugs.
Use this opportunity to inspect the old oil for metal flakes. The presence of flakes or other contaminants can call for a round of troubleshooting.
At the same time, check the main hub mechanical seal—located between the sprocket and track frame—for leaks.
To add new oil, position the plug openings at 12 o’clock and either the 3 or 9 o’clock positions. Using the 12 o’clock opening, pour in the new oil until it just begins to drain out of the 3 or 9 o’clock opening. Tighten the loose plugs, and you’re good to go.
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