Doc's Diesel Transmission Filter Kits: Doc's Diesel Transmission Filters are designed to keep your transmission fluid clean. Transmission Filters are very critical to the longevity of your vehicle and cleanliness of the transmission fluid so Doc's Diesel recommends changing MORE often than OEM recommendations. Reduce costly repairs with regular transmission filter maintenance with Doc's Diesel. Crossover #'s: Doc's DF-440: Motorcraft LC3Z-7G186-A, LC3P-7G186-AC, LC3Z-7F396-A, LC3Z-7F396-B / FT221 Change Interval: (Transmission Filter Kits) *MOST OEM recommendations are based off regular driving and NOT hauling. Doc's Diesel recommends changing transmission filters earlier than OEM recommended for preventative maintenance and ensure longevity of your transmission. 25,000-50,000 miles Recommended 60,000 miles Maximum