Do you know what the most common problem is on a CAT mini excavator final drive? Get ready to find out, and learn how to keep it from happening to your final drive.

Final Drive Duo-Cone Seal

When CAT excavator track drive motors come into the shop for repairs or re-manufacturing, we usually find out that the problem started with a simple leak between the sprocket and the back side of the hydraulic motor. That particular leak is caused by a failed floating face seal, also called a duo-cone seal or a mechanical face seal. It’s job is to keep the gear oil in your final drive.

Gear Oil Leaking from the Final Drive

When a duo-cone seal fails, two things will happen: the gear oil will begin to leak out and contaminants will begin to make their way inside the planetary hub — and this is very bad. The leak will be found between the sprocket and and the final drive. As the leak progresses, you’ll find yourself having to top off the gear oil repeatedly. Keep in mind that this is just a temporary solution and a sign you need to replace the seals. As the seal continues to wear, the leak will get worse and you may end up running your final drive with not enough gear oil in it, which can do very severe damage.

As the seal weakens, debris from the job site can begin to make its way in. This includes abrasive contaminants like sand, grit, and soil that will wreak havoc with your final drive. In fact, we have opened many a final drive core only to discover that instead of gear oil the gear hub is filled with a sludge made up of gear oil mixed with all kinds of debris.

Sources of Duo-Cone Seal Problems

Duo-cone seals wear out and need to be replaced according to manufacturer recommendations (when feasible) or when you notice a leak behind the sprocket. Another cause of failure is related to the excavator undercarriage. If the undercarriage is not kept clean, debris can get packed in so tightly around the final drive motor that it actually pushes the duo-cone seal out of place. The smooth mating face of the seal is vital for it to function properly. When the duo-cone face seals are forced out of place, debris gets wedged between the faces. That abrasive debris can not only forces the faces apart far enough for debris to get inside the final drive, but can scar up the faces and provide additional paths for even more gear oil to leak out.

Preventing Damage From Failed Duo-Cone Seals

If you have a duo-cone seal that is failing, don’t put off getting it replaced. The down-time and basic costs to replace the face seals is far, far less than what it will cost to repair the damage done by ignoring the leak (and that’s assuming your final drive can even be fixed). Next, keep the undercarriage of your CAT excavator clean. Ideally, it should be cleaned at the end of each shift and preferably with a pressure washer to keep debris from building up around the final drive motors.

Final Drive Preventive Maintenance

No matter what brand of excavator you own, leaks should never be neglected. Many times the worst damage we see on excavator final drive motors is due to a leaking face seal that was neglected just a little too long. Save yourself time and money with a little preventative maintenance.