1. Home
  2.  ›
  3. Diesel Locomotives
  4.  ›
  5. U23B

GE's "U23B": Testing The Market For A Mid-Powered Model

Last revised: May 8, 2023

By: Adam Burns

General Electric's U23B was released at a time when both builders opted to unveil mid-powered designs during the height of the horsepower race.

For EMD it was the GP38/GP38-2, a very successful line in its own right that wound up selling more than 2,600 examples between 1966 and 1971.

By the late 1960's, despite some stumbles here and there, GE was finding its footing in the locomotive market.  It's U25B had burst on the scene and sold nearly 500 examples while the later U30C saw more than 600 produced.

Electro-Motive realized that GE posed a very serious threat by the 1960's.  The company had the resources and expertise to stay in the game and it used these strengths to eventually take over the lead in locomotive production by the 1980's.

The U23B proved a mild surprise for GE as interest proved quite strong; when production ended in 1977 the company had sold some 481 examples to seventeen different railroads and utilities.

The Louisville & Nashville picked up the most (90) while Penn Central acquired 77 and Southern Railway another 70.  There were also several other buyers such as the Santa Fe, Missouri Pacific, Chesapeake & Ohio, and Delaware & Hudson.


Delaware & Hudson U23B #2312 (formerly #312), painted for the "Preamble Express," lays over at the Boston & Maine's terminal in Portland, Maine on July 10, 1974. American-Rails.com collection.


When the first U23B rolled out of Erie in August, 1968 (Delaware & Hudson #301), the locomotive market had all but dwindled to two.  American Locomotive was in its final days and would shutter its doors in 1969.

That decade's great horsepower race saw only two builders remain by 1970.  Prior to Alco's exit, the venerable Baldwin Locomotive Works had shuttered in 1956 and upstart Fairbanks-Morse gave up in 1959.

During the 1960s it appeared no one would ever dethrone Electro-Motive; seemingly every model the builder released was a massive success whether it was a cab design or road switcher.

EMD was also a trendsetter with midrange and high horsepower models like the SD45 and GP38.  The company sold thousands of these locomotives and had little competition from GE until the mid-1970s and 1980s.

As Greg McDonnell notes in his book, "U-boats," the U23B was not only intended as a medium horsepower (2,250) locomotive but also one that could handle priority, high speed freights.

It was also more fuel efficient sporting GE's 12-cylinder 7FDL12 prime mover, in place of the typical 16-cylinder variant.

As a result, the locomotive was lighter (121 tons) and featured fewer access doors (six) by comparison to its closest cousin, the U30B (eight).

Interestingly, despite the U23B's modernity within the U-boat line, GE curiously offered an older main generator as an option, the direct current (DC) model GT581 that had been used in Alco's FA/B-2 and RS3.

CSX U23B #3236; June, 1986. This unit was built as Monon #607 and later became Louisville & Nashville #2706 before receiving the Seaboard System livery with the same number. American-Rails.com collection.

Data Sheet and Specifications

Entered Production8/1968 (Delaware & Hudson #301)
Years Produced8/1968 - 6/1977
GE ClassU23B
Engine7FDL12 (12 cylinder)
Engine BuilderGeneral Electric
Length60' 2"
Height (Top Of Rail To Top Of Cab)14' 9"
Width9' 11"
Weight242,000 Lbs
Fuel Capacity1,700 or 2,900 Gallons
Air Compressor3CDC (Westinghouse)
Air Brake Schedule26L (Westinghouse)
Truck TypeSwing Bolster, Drop-Side Equalizer (GSC) or Floating Bolster FB2 (GE)
Truck Wheelbase9' 4"
Wheel Size40"
Traction Motors752 (4), GE
Traction Generator/AlternatorGT581 (DC) or GTA11 (AC), GE
Auxiliary GeneratorGY27, GE
MU (Multiple-Unit)Yes
Dynamic BrakesOptional
Gear Ratio74:18
Tractive Effort (Starting)85,800 Lbs
Tractive Effort (Continuous)57,200 Lbs at 11.9 mph
Top Speed70 mph

Production Roster

Owner Road Number Serial Number Order Number Completion Date Quantity
Delaware & Hudson301-316*36803-3681826018/1968-9/196816
Chesapeake & Ohio2300-2329**37228-3725725089/1969-10/196930
Santa Fe6300-6348*37491-375392514/25166/1970-2/197149
Southern Railway3900-390438392-3839625235/19725
Western Pacific2251-226538397-3841114625/1972-6/197215
Penn Central2700-2749*38506-3855525408/1972-10/197250
Missouri Pacific668-67438758-3876425611/1973-2/19737
Louisville & Nashville2708-2727*38765-3878414101/1973-4/197320
Milwaukee Road4800-4804*38872-3887625756/19735
Southern Railway3905-391439215-3922425765/1973-6/197310
Missouri-Kansas-Texas (Katy)350-352*39225-3922725775/19733
Louisville & Nashville2728-275239257-3928125796/1973-9/197325
Penn Central2750-2776*39305-3933125828/1973-10/197327
Louisville & Nashville2753-277239508-3952714232/1974-4/197420
Southern Railway3915-393439621-3964014225/197420
Missouri Pacific2257-226739905-39915144710/1974-11/197411
Southern Railway3935-395440078-4009714435/1975-7/197520
Louisville & Nashville2800-282440110-40134144412/1974-3/197525
Ferrocarriles Nacionales de México9100-9113*40326-403391484/28123/197514
Ferrocarriles Nacionales de México9114-9121*40340-403471484/28123/1975-5/19758
Ferrocarriles Nacionales de México9122-9129*40348-403551484/28125/1975-6/19758
Missouri Pacific2268-227340356-4036114643/19756
Southern Peru Copper Corporation50-57*40362-4036914623/1975-5/19758
Southern Peru Copper Corporation58-59*40370-40371146310/1975-11/19752
Southern Peru Copper Corporation40-45*40372-40377146310/1975-11/19756
Texas Utilities103*4071914615/19751
Ferrocarril del Pacífico537-546***40820-4082914048/1975-9/197510
Missouri Pacific2274-227840920-4092414076/19765
Southern Railway3955-396941508-41522140911/1976-2/197715
Missouri Pacific2279-228841523-41532141412/1976-1/197710

*  Equipped with the direct current GT581 generator.

** Equipped with Blomberg trucks.

*** De-rated to 1,800 horsepower.  Equipped with the GT581 generator.


  • 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.
  • McDonnell, Greg. U-boats.  Toronto: Stoddart Publishing, 1994.
  • Pinkepank, Jerry A. Diesel Spotter's Guide.  Milwaukee: Kalmbach Publishing Company, 1967.
  • Solomon, Brian. GE Locomotives: 110 Years Of General Electric Motive Power. St. Paul: MBI Publishing, 2003.

721579189247126175723913727969897.jpgConrail U23B #2790 works helper service on Sawdust Hill at Coshocton, Ohio on July 19, 1979. Roger Beighley photo. American-Rails.com collection.

Available truck options were the similar to most other U-boats, either the standard Swing Bolster, Drop-Side Equalizer (AAR Type-B) or the company's own FB2 (Floating Bolster).

In addition to the U23B's success, the locomotive broke new ground for GE by selling to three different companies outside of the United States as well as a private Texas utility.

Domestic lines to purchase the model included the Louisville & Nashville, Penn Central, Southern, Santa Fe, Missouri Pacific, Chesapeake & Ohio, Delaware & Hudson, Western Pacific, Lehigh Valley, Conrail, Monon, Milwaukee Road, and Missouri-Kansas-Texas ("Katy").


Wes Barris's SteamLocomotive.com is simply the best web resource on the study of steam locomotives. 

It is difficult to truly articulate just how much material can be found at this website. 

It is quite staggering and a must visit!