EMD "SD50" Locomotives

Last revised: July 18, 2023

By: Adam Burns

Electro-Motive's SD50 was only marginally successful and the model ran into numerous problems. The design fell far short of the high quality, reliable, long-lasting locomotives that railroads had become so used to purchasing from EMD.

The locomotive was released by the company in the early 1980s and was another attempt to provided a higher-horsepower model to keep pace with General Electric's increasing competition and its C36-7 model that offered more power than the SD40-2.

Unfortunately, EMD rushed the SD50 into production and it not only suffered mechanical problems but also did irreparable damage to the company's reputation as a respectable locomotive builder. 

Interestingly, after the issues with the SD50 were corrected the locomotive did prove quite reliable..  As a result, many many remain in use today. 

Those found on Class I operations, however, no longer operate in their original configuration; CSX has rebuilt their units to SD50-2 and SD50-3 specifications while Norfolk Southern has de-rated theirs to what is termed an SD40E.


Chessie System SD50's at Cumberland, Maryland in June of 1986. Author's collection.


When the SD50 hit the market in 1980 GE was already well established and was providing EMD more competition with every passing year.

Overall the SD50 was very similar to the SD40 series in terms of its layout and design (although it was a bit longer at just over 71 feet and included an extra 600 hp), and its most striking difference was not in appearances at all but what was under the “hood” as the locomotive carried new microprocessors and electronics.

In essence, the locomotive was a transition to the present-day highly computerized models from the then "Dash 2" line that providing EMD with so much success. Unfortunately for EMD the SD50 was not the answer to quelling GE’s increasing market share.

While the locomotive provided sufficient power, rated at 3,600 using General Motors' 16-cylinder model 645F3B prime mover, it was habitually unreliable and prone to numerous mechanical troubles.

Using General Motors' latest D87 traction motor the locomotive could produce tractive effort ratings on par with the SD40-2; 92,000 pounds starting and 82,100 pounds continuous.

To make matters worse the locomotive had a very complicated electrical system and was a headache for maintenance and shop crews.

Not surprisingly because of the SD50’s setback it was mostly a failure in terms of sales and only sold over 400 units when production ended in 1985.

To correct the flaws with the prime mover EMD moved quickly to launch the SD60 model, which it released in 1984.

While the locomotive was more fuel efficient, featured EMD’s new 710-G3A engine, and was much more reliable the failures of the SD50 haunted the original design with less than 600 built.

However, EMD manufactured several variants through 1995 which sold relatively well and by the time production had ended on the SD60 more than 1,100 had been built. In any event, buyers for the SD50 included the Baltimore & Ohio (20, numbered 8576-8595), Chicago & North Western (35, numbered 7000-7034), Chesapeake & Ohio (43, numbered 8553-8575, 8624-8643), Conrail (135, numbered 6700-6834), Rio Grande (17, numbered 5501-5517), Kansas City Southern (11, numbered 703-713), Missouri Pacific (60, numbered 5000-5059), Seaboard System (81, numbered 8500-8552, 8596-8623), Southern (20, numbered 6506-6525).

Missouri Pacific/Union Pacific SD50 #5002, only a few months old, lays over in Fort Worth, Texas in March, 1985. Steve Bledsoe photo. American-Rails.com collection.

While both models were only marginally successful and the market had already turned heavily in favor of GE-built locomotives, the SD50 and SD60 can continue to be found on railroads all across the country, including Class Is.

The SD50 was also the last EMD to be built solely with the standard cab design as the SD60 was offered with the now popular (and mandatory) wide-cab "safety" design (the SD70 was the last EMD locomotive to receive any standard cabs and most were purchased by Norfolk Southern).

It should be also be noted that EMD released the SD50F in 1985. This model was built solely for the Canadian National Railway as a "cowl" design with 60 ultimately constructed. However, like the original SD50 design the SD50F continues to have reliability issues today even though many remain in service.

Data and Specifications

Entered Production5/1981 (Kansas City Southern #704)
Years Produced (SD50)5/1981 - 2/1986
Years Produced (SD50S)12/1980
Engine BuilderGM
Length71' 2"
Height (Top Of Rail To Top Of Cab)15' 7 ½"
Width10' 3"
Weight368,000 Lbs
Fuel Capacity3500 Gallons
Air CompressorGardner-Denver
Air Compressor ModelWBO
Air Brake ManufacturerWestinghouse
Air Brake Schedule26L
Truck TypeHT-C
Truck Wheelbase13' 7"
Wheel Size40"
Traction MotorsD87 (6), GM
Primary GeneratorAR11, GM
Auxiliary GeneratorDelco (A8102)
MU (Multiple-Unit)Yes
Dynamic BrakesYes
Gear Ratio62:15
Tractive Effort (Starting)92,000 Lbs at 25%
Tractive Effort (Continuous)82,100 Lbs at 11 mph
Top Speed65 mph

Production Roster


Total Built = 431

Owner Road Number(s) Serial Number(s) Completion Date
Kansas City Southern 704-713 806044-1 thru 806044-10 5/1981-6/1981
Seaboard System 8500-8524 817046-1 thru 817046-25 1/1983-2/1983
Norfolk Southern 6506-6520 827041-1 thru 827041-15 7/1984
Conrail 6700-6739 837047-1 thru 837047-40 10/1983-12/1983
Seaboard System 8527-8552 837048-1 thru 837048-26 2/1984-3/1984
Chesapeake & Ohio 8553-8575 837057-1 thru 837057-23 1/1984-2/1984
Conrail 6740-6779 837065-1 thru 837065-40 4/1984-6/1984
Seaboard System 8525-8526 837068-1, 837068-2 3/1984
Norfolk Southern 6521-6525 837073-1 thru 837073-5 07/1984
Seaboard System 8596-8602 837080-1 thru 837080-7 6/1984
Baltimore & Ohio 8576-8595 837081-1 thru 837081-20 7/1984-8/1984
Missouri Pacific 5000-5059 847008-1 thru 847008-60 11/1984-12/1984
Seaboard System 8603-8623 847017-1 thru 847017-21 1/1985-2/1985
Denver & Rio Grande Western 5501-5517 847022-1 thru 847022-17 8/1984-9/1984
Conrail 6780-6804 847032-1 thru 847032-25 4/1985-5/1985
Chicago & North Western 7000-7034 847049-1 thru 847049-35 11/1985-12/1985
Conrail 6805-6834 857080-1 thru 857080-30 1/1986-2/1986
Chesapeake & Ohio 8624-8643 857095-1 thru 857095-20 10/1985-11/1985


Total Built = 6

Owner Road Numbers Serial Numbers Completion Date
Norfolk & Western 6500-6505 806030-1 thru 806030-6 12/1980

These six examples were identical to the standard SD50 line except for their SD40-2 frames, which was 2' 4" shorter.  These same frames had been used on Kansas City Southern #700-703, which were designated as SD40X's although were otherwise SD50's internally.

Electro-Motive's use of "S" in the SD50S variant was unknown although apparently meant "short."  The units originally featured an older blower duct but were returned to EMD in October, 1981 and equipped with the free-flow system.

General Motors Diesel Division (GMDD)


Total Built = 60

Owner Road Number(s) Serial Number(s) Order Number Completion Date
Canadian National 5400-5424 A4472-A4496 C455 4/1985-8/1985
Canadian National 5425-5439 A4547-A4561 C455 8/1985-2/1986
Canadian National 5440-5459 A4617-A4636 C461 2/1987-7/1987



T0tal Built = 31

Owner Road Numbers Serial Numbers Completion Date
Saudi Government Railway 3500-3505 808047-1 thru 808047-6 12/1981
Saudi Government Railway 3506-3515 838085-1 thru 838085-10 12/1984
Saudi Government Railway 3516-3522 958646-1 thru 958646-7 11/1997-12/1997
Saudi Government Railway 3523-3530 (assembled by ITS Rail at Paducah, Kentucky) 20038550-1 thru 20038550-8 8/2005

A group of new Missouri Pacific/Union Pacific SD50's, about a month old, at Fort Worth, Texas on December 2, 1984. Steve Bledsoe photo. American-Rails.com collection.

Another variant of the locomotive was the SD50S built just when production on the model was beginning. The "S" regarded a shorter frame making them just over 69 feet length.

All six were purchased the Norfolk & Western (numbered 6500-6505) and its order was completed by December of that year.

In any event, be on the lookout for the locomotives, while together they can hardly be distinguished, compared against other EMDs they can easily be picked out with their extremely long frames compared to others like the SD40 and SD45 series.

Non-Class I operators of the SD50 today include the Reading & Northern, Hudson Bay Railway, and Utah Railway among many others. 


  • Foster, Gerald. A Field Guide To Trains. New York: Houghton Mifflin, 1996.
  • Marre, Louis A. and Pinkepank, Jerry A. Contemporary Diesel Spotter's Guide, The: A Comprehensive Reference Manual To Locomotives Since 1972.  Milwaukee: Kalmbach Publishing Company, 1989.
  • Marre, Louis A. Contemporary Diesel Spotter's Guide, The: A Comprehensive Reference Manual To Locomotives Since 1972, Including Rebuilding, Upgrading, And Leasing Programs (2nd Edition).  Milwaukee: Kalmbach Publishing Company, 1995.
  • Solomon, Brian. American Diesel Locomotive, The. Osceola: MBI Publishing, 2000.
  • Solomon, Brian.  EMD Locomotives.  Minneapolis: MBI Publishing Company, 2006.
  • Solomon, Brian.  GE and EMD Locomotives:  The Illustrated History.  Minneapolis:  Voyageur Press, 2014.
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