Fault Phenomenon: Hitachi ZX330 excavator a metallic impact sound occurs at the hydraulic pump during startup or gear shifting.

Troubleshooting Process:
– Checked coupling: elastic rubber element worn down.
– Checked alignment: engine-pump alignment good.
– Checked splines: splines slightly worn.
– Checked torsion: high engine torsional vibration.

Root Cause: The elastic element in the drive coupling between the engine and hydraulic pump wore out, causing direct metal-to-metal contact.

Required Parts: Hydraulic pump drive coupling elastic element.