Genuine OEM Volkswagen Retaining Washer, part number 01L321166. This washer is designed to prevent a fastener from loosening or to maintain tension within the transmission assembly. It is located as part number 3 in the diagram. This retaining washer has a diameter of 51mm. Genuine OEM retaining washers are precisely engineered to provide the correct clamping force and prevent vibration-induced loosening, ensuring the reliability of transmission components.