Excavator Spare Parts CAT E320GC E323GC Swing Motor Assembly Swing Reducer Gearbox 536-6580 378-9517 Replacement swing motor assembly and swing reducer gearbox designed for CAT E320GC and E323GC excavators. Suitable for maintenance, repair, and overhaul applications where reliable slewing performance and correct fitment are essential. Common Faults 1. Weak swing with slipping during startup 2. Abnormal swing noise, including gear howling or knocking sounds 3. Oil leakage at