• How well the gearbox has been maintained
  • How often the oil has been changed
  • How far the machine tracks
  • The conditions in which the machine has been working

The tell-tale symptom that the seal needs replacing is that the excavator final drive is leaking.

The easiest way to change the floating seals is to remove the drive from the machine. Here are some tips on Excavator Final Drive Removal and Replacement.

It is not recommended to attempt changing the seals in situ as the spring pressure from the new seals will stop you drawing the two halves of the final drive casing close enough to re fit the main nut, ring of bolts, circlip or ‘half-moon’ retaining rings. It also helps to have gravity on your side when setting the new seal as they can be difficult to set in place, let alone when on the machine.

To remove the floating seal, you will need to remove the final drive cover and gearsets so you can see what is holding the two halves of the final drive case together. Here are some possible arrangements:

  • A circlip or 2 x ‘half moon’ retaining rings, simply remove and there will be nothing stopping the two halves of the case being separated.
  • A large nut holding everything together with a locking mechanism stopping the nut spinning loose. Locking mechanisms can be:
    • A pin that can be knocked downwards
    • Pins that need to be drilled and extracted
    • Grub screws either in the top or the side of the nut.

Once removed, the nut can be undone. Depending on the make of the gearbox, nut tension can be anywhere between just over hand tight to 17000NM. Smaller excavator drives generally have much lower torque settings so if you don’t have the correct tool, a couple of taps with a hammer and punch will usually get the nut moving. Gentle heat sometimes helps but be careful not to burn any plastic bearing retainers etc.

Once the two halves of the case are separated, use a pry bar to pop the old seals out. You then need to remove the build-up of debris that gets compacted around where the O-ring sits. If the two tapered housings are not properly clean, you will not be able to set the new seal. Both parts of the housing need to be smooth before you attempt to set the new seal.

Before you fit the new floating seal it’s a good idea to check the main bearing tension. The bearing tension will more than likely need adjusting on a drive with high hours to compensate for bearing wear. You can’t check bearing tension with the seals fitted as the spring pressure from the seal will give you a false reading.

When fitting the new seal, you’re not trying to push it all the way home. You need to make sure the O-ring is caught just inside the lip of the tapered housing just enough so it won’t pop out. The seal will only sit in its proper place when you draw the two halves of the case back together. With the new seals fitted, it can be difficult to draw the two halves of the case together to start the nut/bolts or locate the circlip. In this instance, clamp the hub and spindle together.

This can be a tricky operation so if you don’t want to attempt the job yourself, contact your local FDC dealer.