ALCO C-643DH

The ALCO C-643DH, also called the Century 643DH, was a twin-engine diesel-hydraulic locomotive and the first diesel-hydraulic road switcher built in the United States. It had a C-C wheel arrangement and generated 4,300 horsepower from two 12-cylinder ALCO 251C engines driving a German Voith hydraulic transmission. Only three were built, all for the Southern Pacific in 1964, numbered 9018 to 9020, to join 21 Krauss-Maffei ML-4000 diesel-hydraulics already on the roster. They spent most of their lives in California's flat San Joaquin Valley. Poor performance of diesel-hydraulics and their foreign-made components led Southern Pacific to sell all three for scrap in 1973, and none were preserved.