Cummins 3966721 Piston Skirt

The Cummins 3966721 is an aluminum piston skirt designed for the articulated split piston assembly used in Cummins 8.3L and 8.9L diesel engine platforms. This component mates with a separate steel crown (commonly part numbers 4089963, 4941395, or 4941393) to form a complete piston. It is engineered for high thermal stability and reduced friction in heavy-duty applications. The skirt features anodized or coated surfaces for enhanced scuff resistance during cold starts and high-load operation. This part serves as a direct replacement for OEM 3966721 and superseded alternate number 4945337. It is utilized across on-highway truck, construction machinery, generator set, and marine propulsion installations.