Freewheel Clutch/Pulley for alternator. This unit is standard equipment on all Sprinter alternators (7 Groove - 55 mm OD).
THIS IS A CRITICAL COMPONENT OF THE SERPENTINE BELT SYSTEM AND A KNOWN CAUSE OF BREAKAGE PROBLEMS. IT IS COMMON FOR THIS DECLUTCHING PULLEY TO FAIL, LONG BEFORE THE ALTERNATOR WEARS OUT.
A special tool is required for installation of this unit and are not usually replaceable outside a repair facility. If you are purchasing a new alternator, you will not need to buy this, as the alternator is furnished with a new pulley.