Swing Motor & Reducer Assembly for Caterpillar 305.5 / 306 / 305CR
Model: PCR‑4B‑20, Part No.: 452‑6209
Product Overview
This Swing Motor & Reducer Assembly is a complete slewing power unit for Caterpillar mini excavator Machine. It consists of a radial‑piston Hydraulic piston motor and integrated SWING REDUCER, serving as the core slewing actuator of the excavator hydraulic system. As one of the key parts of excavator rotation drive, this hydraulic motor converts hydraulic pressure energy into mechanical torque, while the built‑in reduction gear reduces speed and amplifies output torque, enabling stable 360‑degree rotation of the upper carriage. Though different from FINAL DRIVE and Travel Assembly used for walking drive, this assembly undertakes all slewing‑movement loads of the equipment. Model PCR‑4B‑20, OEM Part No.452‑6209 features compact layout, built‑in parking brake and relief‑valve protection. It is perfectly interchangeable with original components and widely used for overhaul, repair and aftermarket replacement of Caterpillar 305.5, 306 and 305CR mini excavators. Reliable operation of this Hydraulic piston motor and its SWING REDUCER directly guarantees the safety and stability of the whole hydraulic system.
Technical Specifications
‑ Applicable Machine: Caterpillar 305.5 / 306 / 305CR Mini Excavator
‑ Assembly Type: Complete Swing Drive Unit, including hydraulic motor + SWING REDUCER
‑ Motor Model: PCR‑4B‑20
‑ OEM Part Number: 452‑6209
‑ Motor Category: Radial‑piston Hydraulic piston motor
‑ Max continuous pressure: 245 bar; Peak pressure: 280 bar
‑ Built‑in functions: Mechanical parking brake, anti‑shock relief valve
‑ Installation: Standard flange mounting, pinion output
‑ Working medium: Anti‑wear hydraulic oil for mobile construction hydraulic system
‑ Operating temperature: ‑20℃ ~ +85℃
‑ Feature: Low‑speed high‑torque output, strong overload resistance, compact size, easy installation, strict dimensional match with original excavator Machine, suitable for frequent forward‑reverse slewing operations.
Working Principle
High‑pressure oil delivered from the main control valve of the hydraulic system flows into the hydraulic motor. Inside the Hydraulic piston motor, high‑pressure oil pushes radial pistons to generate rotary power. The rotation speed is reduced and torque is multiplied through the planetary gear set inside the SWING REDUCER, driving the slewing gear to rotate the excavator upper body. The built‑in parking brake automatically locks the output shaft when the Machine stops rotating to prevent platform drifting. Different from FINAL DRIVE and Travel Assembly which provide walking power, this assembly only controls the rotation of the upper frame. Worn pistons, cam rings, gear teeth or failed seals inside will lead to faults such as weak slewing torque, slow rotation, oil leakage, abnormal noise or shaking. Replacing the complete swing motor and reducer assembly can fully restore slewing performance and keep the hydraulic system running stably.
Core Advantages
1. Integrated Hydraulic piston motor and SWING REDUCER one‑piece assembly, simplifies installation and reduces assembly error risk during maintenance of the excavator Machine.
2. Radial‑piston hydraulic motor delivers large starting torque, stable low‑speed performance, adapts to heavy‑load and frequent‑slewing working conditions.
3. Built‑in brake and overload protection valves effectively absorb hydraulic impact, protecting both the hydraulic motor and the whole hydraulic system.
4. High‑precision gear pair inside the SWING REDUCER, low backlash, strong wear resistance, extending the service life of the swing drive unit.
5. Strictly follows OEM dimensions of part 452‑6209, excellent interchangeability, direct replacement without secondary machining, convenient for on‑site overhaul, different from separate maintenance of FINAL DRIVE or Travel Assembly.
Application Range
PCR‑4B‑20 Swing Motor & Reducer Assembly is a dedicated slewing drive component for the hydraulic system of small construction Machine. Specially compatible with Caterpillar 305.5, 306, 305CR mini excavators. Widely supplied for machinery repair workshops, maintenance service stations, construction equipment leasing firms and global spare‑parts dealers. Not used for walking drive (FINAL DRIVE / Travel Assembly), only for upper‑body rotation.
