EMD SD7. The EMD SD7 is a model of 6-axle diesel locomotive built by General Motors Electro-Motive Division between May 1951 and November 1953. It had an EMD 567B 16-cylinder engine producing  for its six traction motors. United States railroads bought 188 units.

This was the first model in EMD's SD (Special Duty) series of locomotives, a lengthened B-B GP7 with a C-C truck arrangement. The two extra axles and traction motors are useful in heavy, low-speed freight service. EMD continues to produce SD series locomotives to this day. Some SD7s both high and short-hood can still be found in service today on shortline railroads and industrial operators, although most Class I roads stopped using these locomotives by the 1970s and 1980s.

Design and production 
The SD7 was conceived as a modification of the existing EMD GP7 with two additional powered axles, one for each truck. Providing two more axles served two purposes: it gave the locomotive more tractive effort compared to the four-axle GP7, and it distributed the locomotive's weight more evenly.

EMD produced its first examples of the SD7 in May 1951, using the 567B engine. Starting in August 1953 a total of 26 SD7s were produced which used either the 567BC engine or the 567C engine.

SD7s were originally set up to run long hood forward, usually noted by the letter "F" painted adjacent to the top step of the long hood boarding steps. Many were later changed or upgraded to run short hood forward as is today's Association of American Railroads standard.

EMD ended production in November 1953 and began producing the SD7's successor, the SD9, in January 1954.

Rebuilds

SD7R 

The Southern Pacific Transportation Company had rebuilt a total of 42 of their SD7 locomotives into the EMD SD7R. They were numbered 1500–1542. The rebuilds had also included upgrades to the electrical systems, traction motors, as well as a changeout of the prime movers swapping the 16-cylinder 567B prime movers with 16-cylinder 645CE prime movers.

Original buyers

Preservation

Currently preserved 
Burlington Northern #6008 (ex-Great Northern #558) is preserved at the Minnesota Transportation Museum in Saint Paul, Minnesota. #6008 was one of the first 20 SD7s to be built in 1952; it's currently under restoration to its original appearance as Great Northern #558.
Southern #197 is preserved at the Virginia Museum of Transportation. It was originally built as Central of Georgia #201.
Southern Pacific #1518 (ex-EMD demonstrator #990), is preserved in operational condition at the Illinois Railway Museum. #1518 was the first SD7 (later converted into an SD7R) built by EMD.
Portland and Western formerly rostered SD7 #1501 (Ex-SP #5280), which was retired in 2023 as part of a fine resolution agreement with the EPA.
The Dakota Southern Railway rosters one SD7, #512 (ex-MILW #2212)
ILSX #1751 (ex-Pennsylvania Railroad #8589) is in operation at Red Trail Energy in Richardton, ND.
Nevada Northern Railway 401 is in service at the Intermountain Power Plant in Delta, Utah. When retired, it will be donated to the Nevada Northern Railway Museum, as part of an agreement with the museum.

References

Further reading

 
 
 
 
 
 
 
 
 
 Diesel Era Volume 6 Number 6 November/December 1995, "EMD's SD7" by Paul K. Withers pp 5–20; 47–50.

External links 

 Locomotive Truck EMD FlexiCoil C

SD07
C-C locomotives
Diesel–electric locomotives of the United States
Railway locomotives introduced in 1952
Freight locomotives
Standard gauge locomotives of the United States