Fix it: how to repair a dumper clutch
After problems arose selecting a gear on a three-ton dumper truck, Jamie Casey set about fixing it. Costing just €230 for parts, here's how he did it
A clutch assembly is a device which, when disengaged, interrupts the power from an engine or motor to a gearbox. This allows the machine to engage or disengage gears, start or stop, and move off smoothly.
A simple clutch assembly has three main parts; the clutch disk, the pressure plate and the release bearing. The pressure plate clamps the clutch disk up against the engine's flywheel, thereby transmitting the power from the engine through the clutch to the gearbox. To interrupt this flow, the operator presses the clutch pedal and releases the pressure plate, meaning the clutch disk is no longer clamped against the flywheel and the drive is interrupted.
There are generally two common faults with clutches. The first is clutch slippage, recognised as a sudden increases in engine revs without the proportional increase in ground speed, especially while pulling a heavy load. In this case, either the pressure plate is getting weak, or the friction surfaces of the clutch disk are becoming worn.
The second fault is a difficulty in selecting a gear, often without clutch slippage. In this case, the release bearing is generally at fault. What happens is the release bearing becomes worn over time, and is no longer able to push on the pressure plate to release the clutch and interrupt the power from the engine.
The clutch featured here is from a three-ton dumper used for muck shifting duties in a landscaping business. Recently it became very difficult to select a gear, so I knew we had some issue with the release bearings. The new clutch kit was sourced in the UK, and cost €230. The entire job took about six man hours from start to finish, and required pretty basic workshop tools, namely sockets, spanners and a hydraulic jack.
A The clutch assembly itself is sandwiched between the gearbox and the engine, so to access it, both of these components must be split apart. The gearbox was unbolted from the engine, and completely removed from the machine.
B The release bearing was assessed and found to be badly damaged. It had been allowed to travel off centre, and had become unevenly worn. Note the difference between the new and old release bearings, left and right, respectively.
C A new clutch kit was sourced. Note the pressure plate in the foreground, the clutch disk at the back and the release bearing to the right.