EMD SD45

EMD SD45 The EMD SD45 was a 3600-horsepower six-axle road locomotive built by Electro-Motive Division during the late 1960s and early 1970s for North American railroads. It combined a high-output twenty-cylinder EMD 645 engine with an SD-series frame derived from earlier EMD SD24 and EMD SD35 designs, aiming to provide increased horsepower for heavy freight services on lines operated by carriers such as Santa Fe, ATSF, Union Pacific, Southern Pacific, and Burlington Northern. The model had a significant influence on motive-power strategy during the late dieselization era and on fleet management practices among Class I railroads including PRR and Illinois Central Gulf.

Design and development

EMD introduced the SD45 amid competition from General Electric and the market shift following orders placed by Northern Pacific Railway and Great Northern Railway, with EMD leveraging experience from the EMD SD24 program and partnerships with the ALCO customer base. Designers targeted enhanced tractive effort for heavy manifest and unit coal trains operating on routes such as the Southern Railway mainlines and the Rock Island Line transcontinental corridors. The twenty-cylinder 645E3 engine aimed to deliver sustained horsepower across gradients found on the Cascade Range and Sierra Nevada subdivisions, while the six-axle (C-C) truck arrangement addressed weight distribution concerns for track classes controlled by bodies like the Interstate Commerce Commission.

Technical specifications

The core of the locomotive was an EMD 20-cylinder 645-series prime mover with a 20× displacement arrangement, producing 3,600 hp and driving a DC generator to feed six DC traction motors mounted on General Steel Castings or Flexicoil trucks. The SD45 featured a 65-foot frame, dynamic braking, multiple-unit compatibility standardized to AAR controls, and air brake systems interoperable with Knorr-Bremse-equipped consists. Cooling systems, fuel capacity, and electrical systems reflected EMD practice of the era and paralleled components used in contemporaries such as the EMD SD40 and GE U30C. Weight distribution and axle loadings were designed to meet American Association of Railroads standards while maximizing adhesion for service on grades like those on the Allegheny Mountains and Appalachian freight corridors.

Production and variants

Production ran from 1965 to 1971 with 786 units constructed for customers including Santa Fe Railway, Denver and Rio Grande Western Railroad, Seaboard Coast Line, Chessie System, and Conrail. Variants and rebuild programs produced subtypes and derivatives: some units were re-engined or downgraded to SD45R-class specifications by shops operated by NRE, General Electric-affiliated maintenance teams, or railroad company shops such as NP shops. Other modifications paralleled rebuilds undertaken on EMD SD40-2 and EMD SD38 fleets, including conversions to 16-cylinder 645 powerplants, electrical upgrades, and the installation of microprocessor controls in later life, reflecting practices employed by Santa Fe and Union Pacific shops.

Service history

The SD45 saw widespread use in heavy-haul freight, manifest, and unit-train coal service on major systems including Santa Fe, Union Pacific, Southern Pacific, N&W, and Penn Central. The model performed notably on high-tonnage routes such as the BNSF Railway predecessor corridors and on unit coal runs serving Appalachian mines to steel mills in regions served by Bethlehem Steel and U.S. Steel. Operational issues including crankcase durability and fuel consumption led several railroads to reassign units to low-speed drag service or to undergo rebuild programs similar to those applied to SD45T-2 and SD40 classes. During corporate mergers and consolidations—Chessie System into CSX, and Burlington Northern merger moves—many SD45s were renumbered, reassigned, or retired, mirroring broader motive-power rationalization trends seen in the Conrail era.

Preservation and disposition

A number of SD45s survive in museums, tourist operations, and on short lines, preserved by institutions such as the Illinois Railway Museum, the Colorado Railroad Museum, and private heritage groups associated with former owners like Santa Fe and Union Pacific. Preservation efforts have included cosmetic restoration, mechanical overhaul, and operation in excursion service on lines owned by entities such as San Luis and Rio Grande Railroad and Durango and Silverton Narrow Gauge Railroad affiliates. Others were cannibalized for parts to support remaining SD40-2 fleets or sold to leasing companies including GATX and GE Capital before final disposition. The class remains of interest to historical societies and railway historians affiliated with universities and archives like the National Railway Historical Society.

Category:Electro-Motive Division locomotives Category:Diesel-electric locomotives of the United States