4440264 Original Excavator Hydraulic Main Pump Ball Bearing for ZX870-5

The Hitachi original excavator hydraulic main pump ball bearing (universal part number: 4440264) is a key supporting component of the core power unit of the hydraulic system. This original spare part is mainly used to support the high-speed rotating shaft of the hydraulic main pump and withstand the radial and axial loads generated by the plunger or gears inside the pump. According to existing information, it is clearly suitable for hydraulic main pumps of large excavator models such as Hitachi ZX890-5A. Given the universality of hydraulic pump design, this bearing may also be applied to other Hitachi large models equipped with similar main pumps, such as the ZX870, ZX850, ZX650 series, etc.

This bearing is the core component in the hydraulic main pump that ensures high-speed, smooth, and precise rotation of the pump shaft. As an original ball bearing (also labeled as needle roller bearing in some materials), its core function is to support the pump shaft with extremely low frictional resistance and transmit the load generated by rotational motion to the pump body. It is usually made of high-quality bearing steel (such as GCr15), which undergoes precision forging, heat treatment (quenching and tempering), and ultra precision grinding, with extremely high dimensional accuracy, rotational accuracy, and excellent fatigue strength and wear resistance.

The maintenance core of this bearing lies in ensuring effective lubrication, preventing contamination, and timely monitoring of abnormal conditions. Due to the bearings being enclosed inside the hydraulic main pump, daily maintenance mainly relies on the overall maintenance of the hydraulic system. Firstly, it is necessary to strictly replace the hydraulic oil and filter element according to the maintenance cycle, and use oil products that meet the original factory standards. This is the key to preventing abrasive wear and extending bearing life.