EMD "SD7" Locomotives

Last revised: June 23, 2023

By: Adam Burns

Electro-Motive's SD7 was essentially the very same thing as a GP7 except that it sported a C-C truck arrangement as opposed to the Geep’s B-B setup (meaning the SD had six axles instead of four).

For EMD, railroads at the time were simply not interested in six-axle locomotives despite their added benefits. Even similar designs being offered by the American Locomotive Company (Alco), Baldwin and Fairbanks Morse all sold poorly.


Still, EMD would continue to offer six-axle variants of popular General Purpose (GP) line until sales finally began to take off with the SD40 of 1966. It is somewhat surprising that despite less than 200 SD7s built a few still remain in regular freight service. 

The irony here, of course, is that when these locomotives were cataloged few railroads were interested.  However, overtime their value increased as the industry recognized the efficiency of six-axle power. 

As a result, many SD7's, and the later SD9, enjoyed many decades of service; examples officially known to be preserved include Central of Georgia #201 at the Virginia Museum of Transportation and EMD's first SD7, demonstrators #990 at the Illinois Railway Museum.


Burlington Northern (Colorado & Southern) SD7 #6077 (built as #817) and GP38-2 #2154 at North Yard in Saginaw, Texas, circa 1983. Mike Bledsoe photo. American-Rails.com collection.

The EMD SD7, which debuted in early 1952 (three years after the release of the GP7) was merely a step up from the GP7 model. It was EMD’s first six-axle (C-C) locomotive and virtually identical to her GP7 sister in every other way.

For instance, the SD7 featured the very same General Motors-built 16-cylinder 567B prime mover and produced the same 1,500 hp.

Its primary purpose was that the extra two axles produced more traction (which allowed the locomotive to handle stiffer grades), allowed for better weight distribution (which was a big plus on light rail and bridges unable to support heavy loads, found on many branch lines) and its Flexicoil trucks allowed for ease of maintenance on its center traction motor.

One additional advantage of the SD7 was that while competitors offered six-axle models based from the same frame of a four-axle, EMD designed its very own frame for the SDs which at 60 feet was about five feet longer than the GP7 (to provide adequate space for the C-C trucks).

The SD7's two additional axles allowed it to produce far more tractive effort than the GP7. Using GM's model D47 traction motor (the GP7 utilized the D27B) the SD7 could produce 75,000 pounds of continuous tractive effort while the GP7 produce roughly half that amount, 40,000 pounds.

Additionally, it offered a starting effort 90,800 pounds compared to the GP7's 65,000 pounds. This also meant that the SD7 could start a train much more quickly than its four-axle counterpart.

75991907762787289019772980.jpgBurlington Northern SD7 #6088, sub-lettered for the Fort Worth & Denver, is seen here in Fort Worth, Texas, circa 1983. Mike Bledsoe photo. American-Rails.com collection.


In the early 1950s railroads still preferred four-axle diesel locomotives in main line freight service and as such, few early model SD designs were constructed.

The SD7, for instance, sold just 188 units, although railroads like the Southern Pacific which had many routes with stiff grades loved the model and used them in regular service for more than four decades.

Railroads that ultimately purchased the SD7 included the Baltimore & Ohio (5, numbered 760–764), Bessemer & Lake Erie (8, numbered 451–455, 801–803), Chicago & North Western (5, numbered 1660–1664), Burlington (37, numbered 300–324, 400–411), Milwaukee Road (24, numbered 2200–2223), Colorado & Southern (10, numbered 810–819), Central of Georgia #201, Denver & Rio Grande Western (5, numbered 5300–5304), Fort Worth & Denver (11, numbered 850–860), Great Northern (23, numbered 560–572), Kennecott Copper #903, Minneapolis & St. Louis (2, numbered 852, 952), Nevada Northern #401, Pennsylvania Railroad (2, numbered 8588–8589), SP (43, numbered 5279–5293, 5308–5335), and Union Pacific (10, numbered 775–784).

Data Sheet and Specifications

Entered Production4/1952 (Milwaukee Road #2200)
Years Produced4/1952 - 11/1953
Engine BuilderGM
Length60' 8 ½"
Height (Top Of Rail To Top Of Cab)15' 0"
Weight360,000 Lbs
Fuel Capacity2400 Gallons
Air CompressorGardner-Denver
Air Compressor ModelWBO
Air Brake ManufacturerWestinghouse
Air Brake Schedule24RL
Truck TypeFlexicoil
Truck Wheelbase13' 7"
Wheel Size40"
Traction MotorsD47 (6), GM
Primary GeneratorD22, GM
Auxiliary GeneratorDelco (A8102)
MU (Multiple-Unit)Yes
Dynamic BrakesYes
Gear Ratio62:15
Tractive Effort (Starting)90,800 Lbs at 25%
Tractive Effort (Continuous)75,000 Lbs at 9.3 mph
Top Speed65 mph

Production Roster

Total Built = 188

Owner Road Number(s) Serial Number(s) Order Number Completion Date
Milwaukee Road 2200-2208 15612-15620 5139 4/1952-6/1952
Milwaukee Road 2209-2211 15621-15623 5201 6/1952, 8/1952
Electro-Motive (Demonstrator) 990 (became Southern Pacific #5308) 15624 7512 10/1952
Great Northern 550-564 16099-16113 5146 5/1952-10/1952
Nevada Northern 401 16824 6397 8/1952
Milwaukee Road 2212-2214 16941-16943 5144 6/1952
Fort Worth & Denver City (Burlington) 850-857 17121-17128 6468 3/1953
Colorado & Southern (Burlington) 810-817 17129-17136 6274 1/1953-2/1953
Bessemer & Lake Erie 801-803 17138-17140 6436 10/1952
Southern Pacific 5279-5293 17144-17156 5157 11/1952-1/1953
Colorado & Southern (Burlington) 818-819 17260-17261 6274 2/1953
Chicago, Burlington & Quincy 400-411 17396-17407 5140 11/1952-12/1952
Minneapolis & St Louis 852, 952 17408-17409 5181 12/1952
Electro-Motive (Demonstrator) 991 (became Baltimore & Ohio #760) 17410 6457 3/1952
Kennecott Copper Corporation 903 17411 6456 12/1952
Great Northern 565-572 17896-17903 5182 3/1953-4/1953
Bessemer & Lake Erie 451-455 17904-17908 5212 4/1953
Fort Worth & Denver City (Burlington) 858-860 17921-17923 5249 10/1953
Denver & Rio Grande Western 5300-5304 18124-18128 5232 5/1953
Chicago & North Western 1661-1664 18223-18227 5185 5/1953
Chicago & North Western 1660 18227 5276 6/1953
Union Pacific 775-781 18284-18290 5244 6/1953
Union Pacific 783-784 18291-18292 5277 6/1953
Union Pacific 782 18293 5278 6/1953
Milwaukee Road 2215-2219 18301-18305 5274 10/1953
Milwaukee Road 2220-2223 18306-18309 6516 10/1953
Central of Georgia 201 18310 6512 5/1953
Chicago, Burlington & Quincy 300-324 18320-18344 5242 5/1953-10/1953
Southern Pacific 5316-5335 18381-18400 5188 8/1953-9/1953
Southern Pacific 5309-5313 18401-18405 5282 7/1953
Southern Pacific 5314 18406 5283 7/1953
Southern Pacific 5315 18407 5286 7/1953
Pennsylvania 8588-8589 18669-18670 5300 10/1953
Baltimore & Ohio 761-764 18683-18686 5303 11/1953

An Electro-Motive builder's photo showcasing new Great Northern SD7 #558 in the summer of 1952. Author's collection.


EMD also constructed two demonstrators, #990 and #991 with the former going to SP and the latter to the B&O.

Despite their relative poor sales numbers, several SD7s remain in service on short lines, more than a half-century since they first left EMD's shops in La Grange, Illinois (a true testament to the reliability of EMD's first generation diesels).

Interestingly, SP kept their SD7s in service through the end with the UP merger in 1996.

Places you can still find SD7s include the Dakota Southern, Tate & Lyle grain elevator in Mattoon, Illinois, Cargill's grain elevator in Litchfield, Minnesota, Peavy grain elevator in Jamestown, North Dakota, Portland & Western Railroad, and a few others are stored away on sidings, some since forgotten. 


  • Foster, Gerald. A Field Guide To Trains. New York: Houghton Mifflin, 1996.
  • Hayden, Bob. Diesel Locomotives: Cyclopedia, Volume 2 (Model Railroader). Milwaukee: Kalmbach Publishing Company, 1980.
  • Marre, Louis A. Diesel Locomotives: The First 50 Years, A Guide To Diesels Built Before 1972.  Milwaukee: Kalmbach Publishing Company, 1995.
  • Pinkepank, Jerry A. Diesel Spotter's Guide.  Milwaukee: Kalmbach Publishing Company, 1967.
  • Schafer, Mike. Vintage Diesel Locomotives. Osceola: MBI Publishing, 1998.
  • Solomon, Brian.  EMD Locomotives.  Minneapolis: MBI Publishing Company, 2006.
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