The Alco C636

The Alco C636 was the builder's final and most powerful six-axle, C-C model. While nearly 100 were built, less than 40 were sold to US railroads, as many systems found the model to be troublesome and unreliable, which certainly reflected the American Locomotive Company's (Alco) perception by the late 1960s. During Alco's early years of its Century line the locomotives proved to be fairly reliable with substantial pulling power, particularly the four-axle models. However, it can probably be accurately assumed that by the last few years of the company's operation as a locomotive builder it let much of its quality control measures slip. Unfortunately, Alco had not been a serious contender as a manufacturer since around the time of World War II as it continued to lose market share to GM's Electro-Motive Division and General Electric from the 1950s onward (GE began building its own diesel after 1959). Interestingly, despite few sales of the C636 (and sister M636) you can still find the locomotive in regular service on shortlines Delaware-Lackawanna and Livonia, Avon & Lakeville.

Conrail C636 #6792 is seen here in Syracuse, New York during 1979. This big Alco was built as Penn Central #6342 in 1968.

The Alco C636 began production in 1967 just a little over one year before the company would outshop its last locomotive. The most powerful standard model diesel locomotive Alco ever built (the company would manufacture a few powerful variants of its Century line for Southern Pacific and Union Pacific known as the C and C855) the C636 could produce 3,600 horsepower using the company's 251E model prime mover. Likely due to Alco's haste to keep pace with GE and EMD the C636 was plagued with problems that this time was not due to the prime mover. Instead, railroads such as the Santa Fe found issues with the traction motor blower failing, which would cause the prime mover to likewise shutdown. Ultimately, this issue and Alco's already shaky reliability in its earlier engine models (such as the 539 and 244) kept many railroads from purchasing the C636.

A pair of Canadian National M636s, #2335 and #2321, have a westbound freight near Burlington, Ontario on August 25, 1974.

Additionally, the high horsepower, six-axle locomotive market had yet to take off although by the late 1960s railroads were beginning to understand the benefits of the setup. For instance, the industry leader at the time, GM's Electro-Motive Division, sold more than 5,000 examples of its four-axle designs during the '60s including the GP35, GP38, GP40, and their variants. In contrast, similar six-axle versions sold just over 500. However, before the decade ended EMD released the SD40 in 1966. It was cataloged about the same time as Alco's C636 and while the SD40 produced less horsepower the industry was impressed with everything it had to offer and would purchase nearly 1,200 of them before being replaced by the updated SD40-2 in the early 1970s that would sell even more.

Canadian Pacific M636 #4732 and an SD40 rest under the sander at Sudbury, Ontario on September 24, 1989.

As powerful as the six-axle Century line was, particularly the C636, railroads came to also dislike them as they caused significant wear to the track structure. For instance, the C636 weighed in at 420,000 pounds while similar models built by EMD and GE weighed much less (the SD40/-2 weighed only 368,000 pounds and the U30C weighed only 363,000 pounds). Unless a railroad used the C636s on a line that was equipped with heavy rail and a high degree of maintenance the infrastructure really took a beating from the locomotives. Even then, most companies were turned away by the weight issues with the earlier C628 and C630. Additionally, with the industry being at its weakest point in its history during the late 1960s and through the 1970s few roads had the monetary resources or track to operate the C636.

Conrail C636 #6783 (former Penn Central #6333 built in 1968) and C630 #6769 (former Pennsylvania #6319 built in 1966) are seen here in Syracuse, New York during 1979. Most Alcos had short careers on Conrail.

In the end, only 83 units of the Alco C636 and M636 (built by the Montreal Locomotive Works) were sold, and of those only 31 were purchased by US railroads (Penn Central, Illinois Central, and Spokane, Portland & Seattle). Alco also built three demonstrators (#636-1, #636-2, #636-3) that were purchased by Québec Cartier Mining. The M636s were purchased by Canadian National, Canadian Pacific, Ferrocaril del Pacfico, and Québec Cartier Mining also picked up a few more. Most of these locomotives were built by MLW after Alco had shuttered its Schenectady, New York plant.

Alco C636 Production Roster

Owner Road Number(s) Quantity Date Built
Alco (Demo)636-1, 636-2, 636-331968
Illinois Central1100-110561968
Penn Central6330-6344151968
Spokane, Portland & Seattle330-335, 340-343101967-1968

Australian-Built C636s (A.E. Goodwin, Ltd.)

Owner Road Number(s) Quantity Date Built
Cliff's Robe River Iron Associates262.001-262.005, 171561971-1972
Hamersley Iron2006-2017121968-1970
Mt. Newman Mining5452-5468171969-1972


CN M636 #2317 lays over in Fort Erie, Ontario on September 23, 1972.

The primary difference between the M636 and the C636 was that the former rode on Dofasco trucks while the latter featured high adhesion trucks. British Columbia Railway's M636's also came equipped with wide cabs.  Interestingly, for the early problems the C636 suffered a handful still operate around the country. Shortline Delaware-Lackawanna operates an astounding three C636s and three M636s. Also, shortline Western New York & Pennsylvania operates three M636s and uses a former C636 for parts.  Finally, for more information about the C636 please check out the charts listed above.

Related Reading

Share Your Thoughts

Have your say about what you just read! Leave me a comment in the box below. Please note that while I strive to present the information as accurately as possible I am aware that there may be errors. If you have potential corrections the help is greatly appreciated.

Check out the website's digital book (E-book), An Atlas To Classic Short Lines, which features system maps and a brief background of 46 different historic railroads.



Related Reading



A History Of The American Locomotive Company (Alco)




A History Of The Montreal Locomotive Works (MLW)


Other Alco Century Models



The C415




The C420




The C424




The C425




The C430




The C628




The C630




The C643DH (Experimental)




The C855 (Experimental)


Alco's Notable Prime Movers



The Model 244




The Model 251