Alco "RSD-5" Locomotives

Last revised: May 7, 2023

By: Adam Burns

The RSD5 was essentially an extension of the RSD4 model as it meant to replace a flaw in the earlier design. After fixing the issue, which had to do with inadequate spacing the RSD5 sold nearly six times as many units as its predecessor.

The model was meant to compete with the Electro-Motive Division's SD7 design, the six-axle cousin of the GP7. Interestingly, despite railroads' disinterest in C-C locomotives at the time, Alco actually outsold its competitor by a few units.

The RSD5 was, of course, nearly identical to the RSD4 although Alco did bump its horsepower rating just slightly, which actually made it a touch more powerful than the SD7. 


Santa Fe RSD5's #2141 and #2161 at Raton, New Mexico, circa 1965. collection.


The RSD5 was rushed into production as a replacement for the earlier RSD4, whose frame was not long enough to support the main generator. As such, at nearly 56 feet, 7 inches the later RSD5 was nearly eight inches longer than its predecessor.

Internally, the model was identical to the RSD4 and both were essentially the same as the four-axle RS3. From a strength standpoint, the RSD5 was slightly better; it offered 1,000 pounds more starting tractive effort (90,000 pounds) and an additional 100 horsepower (1,600 hp). Interestingly, despite the RSD4's issues most railroads that purchased it returned to buy the RSD5.

The RSD5 entered production in 1952 directly after the unsuccessful RSD4 and remained in the company's catalog until 1955. The new model used the same Alco 244 prime mover.


As with all other "D" designated models, the RSD5 used a C-C truck arrangement with all six axles powered. The six axle models were meant to provide a sizable increase in traction and be used on light branch/secondary lines allowing the locomotive's weight to be distributed more evenly over additional axles.

Santa Fe RSD5 #2140 lays over in Colorado Springs, Colorado circa 1965. collection.

In an attempt to probably ease railroads fears over the problematic RSD4, Alco even built an RSD5 demonstrator to prove that the model no longer suffered from its previous issues.

Apparently, the Atchison, Topeka & Santa was quite impressed as they purchased more than 50 units of the design after only picking up ten examples of the RSD4. Additionally, lines like the Chesapeake & Ohio and Southern Pacific, both of which had not even purchased the RSD4 bought nearly 90 of RSD5s between them. 

39689035723785238968932896809379089809.jpgMilwaukee Road RSD5 #571 (built as #2151) at Pigs Eye Yard in St. Paul, Minnesota; August, 1965. Fred Byerly photo. collection.

Data Sheet and Specifications

Alco Class606-DL-360
Entered Production3/1952 (Chesapeake & Ohio #5570)
Years Produced3/1952-3/1956
Model SpecificationE1664/A/B
Engine244, V-12
Carbody StylingAlco
Length (Between Coupler Pulling Faces)56' 5.75"
Weight360,000 Lbs.
Dynamic BrakesOptional
Truck TypeTrimount
Truck Wheelbase12' 6"
Wheel Size40"
Traction MotorsGE 752 (6)
Traction GeneratorGT566
Steam Generator-
Gear Ratio74:18
Tractive Effort Rating78,750 Lbs. at 5.5 MPH
Top Speed60 MPH

Production Roster

Owner Road Number(s) Quantity Date Built
Alco Demonstrator1606 (Became Santa Fe #2157)11952
Birmingham Southern16011953
Chesapeake & Ohio5570-5595261952
Central Railroad Of New Jersey161511953
Chicago & North Western1665-1667, 1684-1690101953-1954
Ferrocarril del Pacífico801-8353511/1953-3/1956
Ferrocarriles Nacionales de México6900-6901211/1955
Milwaukee Road2150-215561953
Santa Fe2110-2162531952-1953
Southern Pacific5294-5339, 5345-5448, 5494-5507641953-1956
St. Louis Southwestern (Cotton Belt)270-27231953
Texas & New Orleans (SP)155-186321953
Utah Railway30611955


  • Foster, Gerald. A Field Guide To Trains. New York: Houghton Mifflin, 1996.
  • Kirkland, John F. Diesel Builders, The:  Volume Two, American Locomotive Company And Montreal Locomotive Works. Glendale: Interurban Press, 1989.
  • Pinkepank, Jerry A. Diesel Spotter's Guide.  Milwaukee: Kalmbach Publishing Company, 1967.
  • Solomon, Brian. Alco Locomotives. Minneapolis: Voyageur Press, 2009.

Santa Fe RSD5 #2122 is between assignments in Barstow, California during the late 1960s. Note the Warbonnet F unit in the background. collection.

Many of the railroads that purchased the RSD5 employed them in heavy freight service such as the Utah Railway, Milwaukee Road, Chicago & North Western, Southern Pacific. The latter three roads particularly loved six axle diesels, practically since they were first manufactured by Alco and EMD.

In any event, for a six-axle model the Alco RSD5 sold relatively well at 204 units for a number of Class I railroads such as the Milwaukee Road, Southern Pacific, Chesapeake & Ohio, and Santa Fe (this also includes the 37 purchased by Mexican lines, Ferrocarril del Pacífico and Ferrocarriles Nacionales de México).  


Today, at least two of these units have been preserved, former Utah Railway #306 (as Nickel Plate #324) and Chicago & North Western #1689. 

After the latter was retired in March, 1981 she went through a number of owners, and even once wore Western Maryland colors leading excursions on the Western Maryland Scenic Railroad.  Today, she has been returned to her C&NW colors thanks to the efforts of the Illinois Railway, which has lovingly restored the locomotive.

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