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EMD's "SD9", The Cadillac: Its Second Six-Axle Model

Last revised: August 27, 2024

By: Adam Burns

The SD9, often nicknamed the "Cadillac" for the smooth ride its Flexicoil trucks provided, was the builder's second six-motored model.  It followed the early SD7, offering a slight increase in horsepower.

While the industry remained settled on four-axle power in general road service, the SD9 nevertheless saw higher sales than its predecessor.  This trend would continue as EMD cataloged increasingly more powerful six-axle models, which drew increasingly more interest.

Externally, there are few visual clues to differentiate the two models as they feature nearly identical carbodies.   One notable buyer of the SD9 was Southern Pacific. 

The company was eager to purchase the SD7 for its secondary lines, and wound up with the largest fleet.  The railroad was so pleased with the model it also amassed the largest roster of SD9s. 

In fact, SP went on to rebuild many SD7s and SD9s, and several were still in regular service when the railroad merged with Union Pacific in 1996.

Photos

A faded Norfolk & Western SD9 soldiers on in service, seen here switching the former Virginian yard in Mullens, West Virginia during October of 1980. Rob Kitchen photo.

History

The SD9 was part of Electro-Motive's so-called "9 Line" which included the F9, SD9, GP9, and E9 which all debuted in 1954.

Among the model's most notable improvements was its use of EMD's latest power plant, the 567C, which offered an additional 250 horsepower.  This engine, as Brian Solomon notes in his book, "Electro-Motive: E Units and F Units," was the most advanced in the series up until that time.

Its upgrades included a redesign of the engine crankcase to withstand a greater beating in daily service, replacement of water seals susceptible to leaking on older model 567s, and an improved cooling circuit.  

Baltimore & Ohio SD9 #1837 is seen here in Cumberland, Maryland during March, 1975. The unit was assigned to hump yard service during this time. American-Rails.com collection.

Reception

The Southern Pacific was one of the first railroads to take notice.  The "Special Duty" line blended increased tractive effort with a lighweight truck to provide exceptional performance on secondary branch lines.

The SP fielded many of these, especially in Oregon, which contained stiff grades.  It quickly tested and soon purchased a fleet of 43 SD7s.  They likewise purchased the most SD9s, buying 150 of the 471 produced domestically (another 44 were acquired by foreign lines).

While the 515 units paled in comparison to the more than 4,000 four-axle GP9s sold, railroads were beginning to take notice of EMD's six-axle line.   Many which had tested the SD7 also purchased the SD9. 

A handsome quartet of Southern Pacific SD9's in the "Black Widow" livery, led by #5472, have freight #805 on the San Joaquin Line, circa 1958. Gordon Glattenberg photo. American-Rails.com collection.

Spotting Features

There were few telltale differences between the SD7 and SD9.  In his book, "A Field Guide To Trains," author Gerald Foster the only notable clue is the marker lights.  On the former these are more inset along the tapered short hood while on the latter they were moved further outward.

Data Sheet and Specifications

Production Roster

Total Built = 515

Export

Rio Grande SD9 #5309 was only a few months old when photographed here by Jackson Thode between assignments at the engine terminal in Provo, Utah in 1957. Author's collection.

In addition, when either model was equipped with dynamic brakes two additional cooling fans were located over the blister.  Buyers of the SD9 were lines one might expect, requiring greater tractive effort in tough environments; the Rio Grande, Missabe, Pennsylvania, Great Northern, and Chicago & Illinois Midland among others.

A number of foreign lines also purchased the model which included Orinoco Mining of Venezuela, Korean National Railroad, and the Chile Exploration Company.

Colorado & Southern (Burlington) SD9 #838 passes the depot and Purina grain elevator in Loveland, Colorado with southbound loads of limestone for the Great Western Sugar factory during the 1960s. Photographer unknown. American-Rails.com collection.

Sources

• 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.

• Solomon, Brian.  EMD Locomotives.  Minneapolis: MBI Publishing Company, 2006.