GE "U23B" Locomotives: Specs, Roster, History

Last revised: January 2, 2025

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 1960s, 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.

Photos

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.

Overview

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.

A trio of newer Lehigh Valley U23B's depart Tifft Street Yard in Buffalo, New York on August 1, 1975. The U-Boats were the last new diesels bought by the LV, financed through the USRA which created Conrail. Doug Kroll photo.

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.

Data Sheet and Specifications

Entered Production	8/1968 (Delaware & Hudson #301)
Years Produced	8/1968 - 6/1977
GE Class	U23B
Engine	7FDL12 (12 cylinder)
Engine Builder	General Electric
Horsepower	2250
RPM	1050
Length	60' 2"
Height (Top Of Rail To Top Of Cab)	14' 9"
Width	9' 11"
Weight	242,000 Lbs
Fuel Capacity	1,700 or 2,900 Gallons
Air Compressor	3CDC (Westinghouse)
Air Brake Schedule	26L (Westinghouse)
Trucks	B-B
Truck Type	Swing Bolster, Drop-Side Equalizer (GSC) or Floating Bolster FB2 (GE)
Truck Wheelbase	9' 4"
Wheel Size	40"
Traction Motors	752 (4), GE
Traction Generator/Alternator	GT581 (DC) or GTA11 (AC), GE
Auxiliary Generator	GY27, GE
MU (Multiple-Unit)	Yes
Dynamic Brakes	Optional
Gear Ratio	74:18
Tractive Effort (Starting)	85,800 Lbs
Tractive Effort (Continuous)	57,200 Lbs at 11.9 mph
Top Speed	70 mph

Production Roster

Owner	Road Number	Serial Number	Order Number	Completion Date	Quantity
Delaware & Hudson	301-316*	36803-36818	2601	8/1968-9/1968	16
Chesapeake & Ohio	2300-2329**	37228-37257	2508	9/1969-10/1969	30
Monon	601-608*	37293-37300	2512	3/1970-5/1970	8
Santa Fe	6300-6348*	37491-37539	2514/2516	6/1970-2/1971	49
Southern Railway	3900-3904	38392-38396	2523	5/1972	5
Western Pacific	2251-2265	38397-38411	1462	5/1972-6/1972	15
Penn Central	2700-2749*	38506-38555	2540	8/1972-10/1972	50
Missouri Pacific	668-674	38758-38764	2561	1/1973-2/1973	7
Louisville & Nashville	2708-2727*	38765-38784	1410	1/1973-4/1973	20
Milwaukee Road	4800-4804*	38872-38876	2575	6/1973	5
Southern Railway	3905-3914	39215-39224	2576	5/1973-6/1973	10
Missouri-Kansas-Texas (Katy)	350-352*	39225-39227	2577	5/1973	3
Louisville & Nashville	2728-2752	39257-39281	2579	6/1973-9/1973	25
Penn Central	2750-2776*	39305-39331	2582	8/1973-10/1973	27
Louisville & Nashville	2753-2772	39508-39527	1423	2/1974-4/1974	20
Southern Railway	3915-3934	39621-39640	1422	5/1974	20
Missouri Pacific	2257-2267	39905-39915	1447	10/1974-11/1974	11
Southern Railway	3935-3954	40078-40097	1443	5/1975-7/1975	20
Louisville & Nashville	2800-2824	40110-40134	1444	12/1974-3/1975	25
Ferrocarriles Nacionales de México	9100-9113*	40326-40339	1484/2812	3/1975	14
Ferrocarriles Nacionales de México	9114-9121*	40340-40347	1484/2812	3/1975-5/1975	8
Ferrocarriles Nacionales de México	9122-9129*	40348-40355	1484/2812	5/1975-6/1975	8
Missouri Pacific	2268-2273	40356-40361	1464	3/1975	6
Southern Peru Copper Corporation	50-57*	40362-40369	1462	3/1975-5/1975	8
Southern Peru Copper Corporation	58-59*	40370-40371	1463	10/1975-11/1975	2
Southern Peru Copper Corporation	40-45*	40372-40377	1463	10/1975-11/1975	6
Texas Utilities	103*	40719	1461	5/1975	1
Ferrocarril del Pacífico	537-546***	40820-40829	1404	8/1975-9/1975	10
Missouri Pacific	2274-2278	40920-40924	1407	6/1976	5
Southern Railway	3955-3969	41508-41522	1409	11/1976-2/1977	15
Missouri Pacific	2279-2288	41523-41532	1414	12/1976-1/1977	10
Conrail	2789-2798	41584-41593	1412	5/1977-6/1977	10

* Equipped with the direct current GT581 generator.

** Equipped with Blomberg trucks.

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

Sources

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.

Conrail 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").