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"GP39" and "GP39-2": EMD's Mid-Powered 645 Model

Published: January 5, 2025

By: Adam Burns

Introduced in 1969, the GP39 was part of the EMD's latest line of 645-powered models. Also regarded as second-generation variants, this period was marked by a significant shift in the industry as companies sought more economical and efficient locomotives to replace their aging first-generation fleets. 

With the GP39, offering 2,300 horsepower, EMD aimed to capture the mid-powered market with railroads interested in a more powerful but fuel efficient model which utilized only a 12-cylinder 645 prime mover.

However, the industry was disinterested in dealing with the increased maintenance costs of a turocharger and ultimately only 23 examples of the initial model sold.  The later Dash 2 variant was more successful although most went to the Santa Fe.

Chesapeake & Ohio GP39 #3910 - one of twenty Chessie purchased - is seen here at Lima, Ohio on May 22, 1981. Doug Kroll photo.

Background

The GP39 entered EMD's catalog in the spring of 1969, a time when the builder's new 645 line was selling quite well.  As a result of its success, the company believed a mid-powered, turbocharged design would also enjoy high sales.

The model was powered by the 645E3C prime mover—a turbocharged, two-stroke diesel engine that encapsulates the engineering prowess of its era. The 12-cylinder powerplant delivered robust performance and could perform a variety of tasks, from switching to general road service.

One unique aspect was its use of advanced technology for its time. The model integrated the AR10 alternator, providing improved electrical efficiency and performance over the earlier models that used generators. 

Despite its engineering strengths, the GP39 experienced limited production numbers. Only 23 units were built; 20 were sold to the Chesapeake & Ohio while the Atlanta & St Andrews Bay purchased a single unit.  In addition, Kennecott Copper acquired two units with DC main generators, which were classified GP39DC.

In pursuit of evolving its design further, EMD introduced the GP39-2 in August, 1974. This variant featured largely internal improvements.

Noteworthily, the model incorporated modular electrical components enhancing maintenance efficiency—forward thinking for the era.  In addition, it offered greater tractive effort, reduced exhaust emissisions, and more robust engine components.

Interestingly, the Dash 2 variant may have never been cataloged if not for the Santa Fe's interest in turbocharged models and requested such in the GP39 line.  

Of note was the 33 examples purchased by Kennecott Copper.  As Greg McDonnell notes in his book, "Locomotives: The Modern Diesel & Electric Reference, Second Edition," all but four were customized with a special high cab (and nose) and underclearance for open-pit mining operations.

As a historical footnote, Katy 360-379 were the final GP39-2s produced, outshopped in the spring of 1984.  They were equipped with a unique GP49 carbody.

A pair of Kennecott Copper's unique GP39-2s, #792 and #799, sporting the high cabs are switching at Garfield, Utah on June 13, 2004. Doug Kroll photo.

Data Sheet

Production Roster

GP39

GP39DC

GP39-2

Burlington Northern GP39-2 #2713 and GP35 #2526 are both seen here at Portland, Oregon on May 23, 1984. Doug Kroll photo.

Legacy

While the GP39 did not achieve widespread production success, its legacy is significant for several reasons. It highlighted the need for varied power options in locomotive fleets, influencing subsequent models and industry decisions.

The model exemplified the value of combining moderate horsepower with advanced electrical systems, paving the way for future developments in diesel-electric technology. Today, a few can still be found in service around the country, such as on the Reading & Northern and Freeport-McMoRan (Arizona).