Powerful even by today’s standards, EMD’s SD45 had the most horsepower of any six-axle unit from the company until the SD50 of nearly two decades later. Distinctive for its flared radiators, the SD45 derived its power from a 20-cylinder version of the 645 prime mover. Introduced in 1965, the SD45 was sold until 1971, but the type was experience problems early on, especially with crankshaft failures, and the only slightly less powerful SD40, with a more reliable 16-cylinder 645, was to gain favor.
The SDP45 had an extended frame and rear hood to allow the fitting of a steam generator; those purchased by the Great Northern were later used in freight service by successor Burlington Northern, while the Southern Pacific units were used in commuter service for years after the advent of Amtrak, before ending their lives hauling freight. The Erie Lackawanna was the major user, although their units did not have steam generators, the extra length being used to accommodate larger fuel tanks for long-range freight service.The SD45-2 model, built until 1975, introduced the Dash-2 electric system, and did not have the flared radiators, while the SD45T-2 tunnel motor version had the intakes moved down low to suck in the cooler air closer to the bottom of tunnels.
Many of the rebuilt SD45s operating today originated with the PRR; these units were historic in that they were the last Pennsy units to be delivered, with the last few arriving after the Penn Central merger. After serving through the PC years, the SD45s were retired by Conrail in 1981-83, with many going to the C&NW, and then being subsequently sold for rebuilding.
Walter B. Feibelman “Rails to Pittsburgh 1945-1970: Steam, Diesel and Electrics in Pittsburgh Pennsylvania” P.96 photo of SD45 demonstrator 4554 at PRR’s Conway Yard; p.110 photo of Penn Central SD45 6210 at Horseshoe Curve.