Final drive maintenance – important information

18.03.2024

I don’t think anyone needs to be convinced that repairing an excavator’s final drive is an expensive and time-consuming process. This is not only about the cost of the parts themselves, but also about losses resulting from machine downtime. Regular inspection and maintenance of this element of the suspension system is therefore crucial for optimal operation of the excavator.

Why is regular final drive maintenance essential?

Final drives for tracked excavators are exposed to heavy loads, which means that without proper maintenance, they wear out quickly. Leaving them alone for a long time is not only a risk of permanent damage, but also a threat to the entire hydraulic system. Contamination resulting from wear of the final drive’s working elements may be transferred along with the oil to other parts of the machine connected to it, causing extensive failures.

It’s better to take a few minutes and perform regular maintenance on your excavator’s final drive than to waste a lot of time and money on repairs. If for some reason you need to replace your final drive with a new one, we have many replacement final drives for crawler excavators, of popular brands (such as JCB, Bobcat, Case, or Airman). 

The most important maintenance tasks

To ensure proper operation of the final drive’s and to avoid serious failure, the following activities should be performed regularly:

1. Checking the final drive gear oil

Experts say that the gear oil level should be checked after installing a new final drive, after 100–150 hours of operation, and then afterwards 500–800 hours of operation. Detailed information is contained in the operator’s manual (O&M). You can check the oil level in a few simple steps:

  • While looking at the cover plate of your final drive motor (after removing the cover on the outside), you should be able to notice two or three plugs (depending on the model). A common two plug system will mostly be arranged at an angle of 90° to each other. However, in the case of a three plug system, they will usually be in one line (two at opposite edges and one in the middle.) You should arrange the final drive so that:
    By two plugs set – the upper one is at the 12 o’clock and the bottom plug one is at the 3 o’clock position (the manufacturer’s logo or hole sign will help for better orientation).
    By three plugs – they should be positioned so that the filler hole cap is at the top (usually marked as “fill line”).
  • Carefully clean the final drive, and remove any debris (sand, mud, dirt, dirt, etc.) especially around the plugs, so that it does not get into the gear oil, while removing the drain plug.
  • Slowly remove plugs (both by two plugs, and by three plugs, remove one plug in the middle and one plug at the top.) The plugs may need to be loosened with a hammer.
  • If there is enough gear oil in the drive, it should be level with the centre hole at 3 o’clock. If there is less gear oil, you need to add oil to equalize with the mentioned hole.
  • After topping off the oil, put in new plugs.
    There is one rule – gear oil should not exceed half of the capacity of the final drive.

2. Change out the gear oil

The gear oil (or gear lube) should be changed out completely in accordance with the manufacturer’s recommendations included in the operator’s manual. It is best to do this while the oil is still warm, as this will make it easier to drain out. To change out the gear oil, follow these steps:

  • Set the final drive so that the mentioned plugs are at 3 and 6 o’clock (at two holes) or the one marked “drain” is at the bottom (at three holes). The lower hole will be used for draining out, and the upper/middle hole will be used to ventilate the system.
  • Clean the surface of the final drive and first remove the lower cap and then slowly the upper cap. If it is necessary, use a hammer to loosen them.
  • While the oil will drain out through the lower hole, make sure there are no metallic shavings in it. If they appear, it means that the gear mechanism is damaged and the final drive needs to be serviced or replaced with a new one.
  • All the oil has drained out – start pouring new oil – in the case of two holes, simply turn them over so that the lower one is on top. In the case of three holes, the third one is used for adding oil (marked “fill”).
  • Pour the new oil through the top hole. CAUTION – remember to pour the same type of oil that was used before, NEVER MIX THEM.
  • After filling the final drive to the appropriate level, install new plugs.

3. Check the Case Drain Filter

Almost every final drive motor is equipped with a case drain filter located on the return line to the hydraulic tank. Its task is to catch impurities from the hydraulic fluid while it leaves the power motors. If this filter is not checked and replaced regularly, it can become clogged. This might cause pressure to build up in the system’s components, which can eventually rupture them.

Locating this filter may be a bit problematic – there may be up to 5 hydraulic filters in an excavator, and it is best to check with the service centre. They will check the model and serial number of the excavator to check what specific hydraulic filters are there, and where they are located. The frequency of their replacement, and exact technique, should be checked in the machine’s manual.

Remove the filter and connect the drain lines to avoid potential contamination and loss of hydraulic fluid. Unscrew the filter and check the condition of the filter element – it will usually be conical and made of sintered bronze. The filter elements should be replaced if they are no longer bronze.

4. A leaking final drive

Leakage checks should be practiced daily once over before starting work. There are two different forms of leaks on a final drive: hydraulic leaks and gear oil leaks.

A gear leak can be detected by looking for traces of oil behind the gear or for drops of oil on the tracks of a tracked excavator. Such leaks are most often related to the mechanical face seal and should be addressed as soon as possible.

Hydraulic fluid leaks may be the result of a leaking hose (which can be repaired quickly) or problems with the hydraulic motor – hydraulic oil chemical degradation, or final drive – most likely a clogged filter.

How often should I do final drive maintenance?

There is no clear answer to this question – it all depends on the specific excavator model and the intensity of its use. Remember that preventative maintenance for final drives is important.

The starting point for establishing a maintenance schedule should be the Operation and Maintenance Manual prepared by the manufacturer. It was created by engineers responsible for the machine design, who know perfectly when maintenance is needed. Of course, the frequency of maintenance work will increase with the intensity of use of the travel motor. You should also constantly monitor the condition of the final drive and, if necessary, top up the oil level.

Final drive maintenance – summary

Excavators are the most frequently used construction machines, which are intensively used in difficult terrain. The use of a travel motor on the drive wheels makes it easier for the machine to move off-road. It is essential to maintain final drive regularly. It will help to avoid expensive and serious breakdowns and increase the final drive’s lifespan.

Furthermore, it is worth remembering that repairing hydraulic motors is rarely profitable and in case of more serious failures, it is better to replace the entire final drives at once.

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