This time a CIFA truck mixer pump came in with an oil leak from the drum drive gearbox. Replacing the seal itself is not complicated – the real challenge is getting to the gearbox. The video shows how to safely support the drum, remove the gearbox, reseal it and refit it.
Removal: the motor first, then the drum
The first step is removing the hydraulic motor that drives the gearbox and drum. The motor also acts as the drum brake, and to reach the remaining bolts the drum has to be rotated. We did not disconnect the hoses – there were no leaks there, so we simply loosened them and moved the motor aside.
To make room for the gearbox we removed the bracket supporting the main boom and moved the cooler aside. Then came the tedious part: dozens of Allen bolts joining the gearbox to the drum, with difficult access. The bolts fixing the gearbox to the frame (three on each side) are removed by holding them with a wrench through service openings.
Securing the drum
Once the gearbox is unbolted, the drum would slide forward and could hit the frame. That is why, before removal, we secured it from the rear with a ratchet strap and then lifted it with a forklift. For the duration of the repair the drum was additionally supported so that it did not rest on the forks.
Gearbox repair in the workshop
After dismantling the gearbox the cause was obvious: the main seal had aged – the rubber had hardened, stopped working and no longer sealed, and the dust shield was damaged. All parts were washed, and during assembly we:
- pressed in the new seal (lightly lubricated before fitting) and the shaft onto its bearing,
- oiled the main bearing and secured the shaft with its nut,
- fitted the planet gears of each planetary stage, oiling every bearing and gear,
- fitted a new O-ring under the housing and bolted the gearbox together.
Refitting and start-up
The gearbox went back in on the forklift, was precisely aligned and bolted to the drum and then to the frame. Finally we fitted the cleaned drum motor with a new seal and filled the gearbox with gear oil supplied by the customer – the level is checked through the sight glass. The drum turns quietly with no leaks, and the machine went back to work.
A word of praise for the operator: the machine arrived clean and well maintained, so we could start work immediately.
Takeaways
- Gearbox seals age over time – they harden and lose their sealing ability, even without mechanical damage.
- The key to a safe repair is securing the drum against sliding before the gearbox is unbolted.
- A clean machine shortens service time and cost.
Having problems with the hydraulics or gearboxes in your machine? Check our construction machinery service.
Watch the repair video: How Do You Get In There? Repairing the Drum Drive Gearbox of a CIFA Truck Mixer Pump
