GE "U25B" Locomotives: Specs, Roster, History

Last revised: January 10, 2025

The U25B was General Electric's entry into diesel locomotive manufacturing as an independent builder. The company, however, was no stranger to locomotive production.

As Brian Solomon notes in his book, "GE Locomotives," it built its first electric locomotive for main line applications in 1893. It was a simple two-axle design that weighed 30 tons and could operate at speeds up to 30 mph.

From this early period GE began refining electrical gearing and aided the Baltimore & Ohio in the electrification of its Howard Street Tunnel project in 1895.

It then teamed up with American Locomotive in the further development of electric locomotives for main line service. However, whereas Alco designed the carbodies and was responsible for manufacturing, GE supplied most electrical parts and components.

By 1904 the company was competing head-to-head with Westinghouse/Baldwin in electric traction systems.

As such, GE was well suited for the future diesel locomotive market. It started small, supplying generator and electric equipment for the first diesel-electric built for Southern Pacific in 1904-1905. A year later it built its first gas-electric car (1906).

Rock Island U25B, #209, sits on display at Illinois Central's 31st Street Yard in Chicago during a trade show being held that year in September of 1963. This locomotive, an Oroville Dam U25C (partly visible in the photo), and a Union Pacific U50 were the GE products featured. In addition, Electro-Motive had a GP35 and DD35 while Alco featured a Green Bay & Western C424. American-Rails.com collection.

Overview

In 1917, GE was back at it when it began testing an experimental model utilizing a GM-50 prime mover (a V-8 diesel engine designed by GE).

A year later it launched formal production of these 225 horsepower machines; the line was largely considered a failure although a few were sold; one to the Jay Street Connecting Railroad (#4), another to the city of Baltimore and finally one to the U.S. Army.

GE then went on to produce a successful line of switchers beginning in 1940 such as the 25-tonner, 44-tonner, 80-tonner, 125-tonner, and more.

At the same time, GE continued its partnership with Alco when the Schenectady builder began production of main line diesels in late 1939.

For more than a decade the duo tried to keep pace with General Motors' Electro-Motive Division, with mixed results. During this time, GE provided electrical components while Alco designed the carbodies and supplied the prime mover.

The two manufactured an array of now classic models like the FA, PA, RS1, and RS3. However, Alco was failing to keep pace with EMD.

A trio of Erie Lackawanna U25B's, led by #2526, lead a general manifest east through Binghamton, New York during February of 1966. American-Rails.com collection.

A leader in many sectors outside of railroading, GE decided to end its partnership with Alco in 1953 and strike out on its own. After severing ties, GE ramped up production at its Erie, Pennsylvania facility to develop its own road switcher.

GE elected to build a new design entirely from scratch. The very first was an unclassified, testbed set of A-B-B-A cab units which somewhat resembled an EMD F model although with a less graceful carbody.

The quartet was out-shopped in September, 1954 and featured Cooper-Bessemer FVA12LT engines capable of producing 1,200 horsepower per unit.

The set tested on the Erie Railroad and even wore Erie colors although remained wholly GE-owned. After testing that ran through 1959, they were returned to the Erie plant and rebuilt with 2,000 horsepower, FVBL12T engines. GE subsequently reclassified the locomotives as the UM20B.

St. Louis-San Francisco (Frisco) U25B #813 is seen here at the road's engine terminal in Springfield, Missouri, circa 1969. Mac Owen photo. American-Rails.com collection.

They were then painted in Union Pacific colors and given numbers 620-620B and 621-621B, remaining in service until October, 1963.

In 1956 General Electric built 10 model UD18's for Mexican carrier Ferrocarriles Nacionales de México (NdeM). They sported an 7FDL12 prime mover capable of producing 1,800 horsepower. The units also featured a road-switcher carbody that closely resembled what became GE's first production design, the U25B.

A trio of Milwaukee Road U25Bs, led by #5000, have a westbound freight passing Substation #13 at East Portal, Montana on St. Paul Pass in August of 1970. American-Rails.com collection.

Demonstrators

With ample resources available, the company spared no expense marketing this new locomotive. GE would ultimately build four different sets of U25B demonstrators that totaled 16 units (all but the original two were sold).

As Greg McDonnell notes in his book, "U-Boats," the U25B featured an array of groundbreaking technologies such as "a central air system, pressurized engine and control compartments, advanced wheel slip control, and an improved cooling system."

Union Pacific U25B #629, featuring a classic high, short hood, was photographed here in Denver, Colorado on April 8, 1971. Also note the rare RS27 in the background, built as Alco demonstrator #640-2. Author's collection.

In May and June of 1959, GE released its initial two U25B demonstrators, #751-752. At the time these locomotives were referred to as the "XP24" which stood for:

Export Test Unit, 2400 Horsepower

The pair spent about a year testing around the country before being sent back to Erie where they were upgraded to 2,500 horsepower and reclassified as the U25B.

General Electric U25B demonstrators, #2501-2504, layover at the Reading's Erie Avenue Yard in Philadelphia during April of 1962. #2501, furthest to the right, was a low-nose variant while the other three units all wore high, short hoods. The quartet was later purchased by Union Pacific (#633-636) in July of that year. Author's collection.

The new model's designation was as follows:

"U" referred to GE's Universal Series

"25" designated the horsepower rating (2,500)

"B" referred to the unit's four-axle, B-B truck design

The locomotive utilized an updated version of the company's new prime mover, the 7FDL16 prime mover. It was a spin-off of the Copper-Bessemer designs from which it was based.

When GE elected to enter main line locomotive production it had selected Copper-Bessemer power plants for its new models. The engine was a four-cycle, turbo-charged variant somewhat similar to Alco's model 251.

With the resources, expertise, and electrical components already in its arsenal, GE simply had to refine its product and greatly increase the engine's horsepower output.

The company did both and its efforts paid off. Railroads quickly came to like the model's simplicity, horsepower, and ease of maintenance.

A relatively light locomotive for a road switcher, weighing just 126 tons, it could produce excellent tractive effort for its size; 75,000 pounds starting and 64,000 pounds continuous.

The U25B was not without its issues, notably GE's new 7FDL16 engine. However, the company provided warranties and troubleshooting support; both not only increased sales of the U25B but also future models.

St. Louis-San Francisco ("Frisco") U25B #820 at Springfield, Missouri, circa 1970. American-Rails.com collection.

Data Sheet and Specifications

Entered Production	4/1959 (GE Demonstrator #751 and #752)
Years Produced	4/1959 - 2/1966
GE Class	U25B
Engine	7FDL16 (16 cylinder)
Engine Builder	General Electric
Horsepower	2500
RPM	1050
Length	60' 2"
Height (Top Of Rail To Top Of Cab)	14' 2"
Width	9' 11"
Weight	252,000 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)
Truck Wheelbase	9' 4"
Wheel Size	40"
Traction Motors	752 (4), GE
Traction Generator	GT598, GE
Auxiliary Generator	GY27, GE
MU (Multiple-Unit)	Yes
Dynamic Brakes	Optional
Gear Ratio	74:18
Tractive Effort (Starting)	75,000 Lbs
Tractive Effort (Continuous)	64,000 Lbs at 10.7 mph
Top Speed	70 mph

Production Roster

Owner	Road Number	Serial Number	Order Number	Completion Date	Quantity
General Electric (Demonstrator)	751*	33505	-	4/1959	1
General Electric (Demonstrator)	752*	33506	-	6/1959	1
General Electric (Demonstrator)	753-756**	34220-34223	1311	1/1962-2/1961	3
Union Pacific	625-627***	34224-34226	1310	8/1961	3
St. Louis-San Francisco Railway (Frisco)	800***	34227	1311	12/1961	1
Union Pacific	628***	34228	1300	8/1961	1
St. Louis-San Francisco Railway (Frisco)	803***	34229	1311	12/1961	1
Union Pacific	631***	34230	1300	5/1962	1
St. Louis-San Francisco Railway (Frisco)	801***	34231	1311	11/1961	1
St. Louis-San Francisco Railway (Frisco)	802***	34232	1311	11/1961	1
Union Pacific	630***	34233	1300	5/1962	1
Union Pacific	632***	34235	1300	5/1962	1
General Electric (Demonstrator)	2501-2502****	34234, 34236	1300	2/1962	2
Union Pacific	629***	34238	1300	5/1962	1
General Electric (Demonstrator)	2503-2504*****	34237, 34239	1300	2/1962	2
Southern Pacific	7500-7505	34240-34245	1325	3/1962-4/1962	6
Santa Fe	1600-1603	34246-34249	1321	4/1962	4
Santa Fe	1604-1607	34250-34253	1321	5/1962	4
Wabash	500	34254	1330	5/1962	1
Wabash	514	34255	1330	5/1962	1
Wabash	502-505	34256-34259	1330	5/1962	3
Santa Fe	1608-1615	34277-34284	1371	2/1963	8
Wabash	506-508	34519-34521	1330	8/1962	3
Wabash	501	34522	1330	8/1962	1
Wabash	510	34523	1330	8/1962	1
Wabash	509	34524	1330	8/1962	1
Wabash	511	34525	1330	8/1962	1
Wabash	512-513	34526-34527	1330	8/1962	2
Pennsylvania	2500-2506	34528-34534	1345	8/1962	7
Union Pacific	637-640	34535-34538	1340	8/1962-9/1962	4
Pennsylvania	2507-2528	34539-34560	1361	9/1962-10/1962	22
General Electric (Demonstrator)	51-54******	34561-34562, 34564-34565	1364	12/1962	4
St. Louis-San Francisco Railway (Frisco)	811	34563	1364	7/1963	1
Chesapeake & Ohio	2500-2504	34566-34570	1383	8/1963	5
St. Louis-San Francisco Railway (Frisco)	809	34571	1364	7/1963	1
St. Louis-San Francisco Railway (Frisco)	810	34572	1364	7/1963	1
St. Louis-San Francisco Railway (Frisco)	808	34573	1364	7/1963	1
Southern Pacific	7515-7527	34685-34697	1372	3/1963	13
Southern Pacific	7506-7514	34698-34706	1376	3/1963-4/1963	9
Rock Island	200-205	34707-34712	1378	5/1963	6
Louisville & Nashville	1600-1604	34713-34717	1379	6/1963	5
Rock Island	206-211	34718-34723	1378	9/1963-10/1963	6
Chesapeake & Ohio	2505-2507	34724-34726	1383	8/1963	3
Louisville & Nashville	1605-1608	34727-34730	1379	8/1963	4
Chesapeake & Ohio	2508-2537	34731-34760	1381	10/1963-1/1964	30
Louisville & Nashville	1609-1612	34761-34764	1384	11/1963-12/1963	4
Southern Pacific	7528-7564	34765-34801	1405	1/1964-3/1964	37
Great Northern	2500-2506	34962-34968	1415	4/1964	7
Great Northern	2507-2508	34984-34985	1415	4/1964	2
New York Central	2500-2529	34986-35015	1418	1/1964-9/1964	30
Rock Island	212-224	35111-35123	1421	4/1964-6/1964	13
Pennsylvania	2529-2533	35124-35128	1423	9/1964	5
Louisville & Nashville	1613-1626	35130-35143	1426	6/1964-10/1964	14
Erie Lackawanna	2501-2512	35160-35171	1432	9/1964-10/1964	12
Chicago, Burlington & Quincy	100-105	35194-35199	1435	9/1964-10/1964	6
New York, New Haven & Hartford	2500-2509	35394-35403	1437	10/1964	10
New York Central	2530-2559	35423-35452	1442	11/1964-2/1965	30
St. Louis-San Francisco Railway (Frisco)	816-823	35522-35529	1439	3/1965	8
Pennsylvania	2534-2548	35530-35544	1444	2/1965-3/1965	15
Great Northern	2509-2523	35566-35580	1451	4/1965-5/1965	15
Norfolk & Western	3515	35581	1446	2/1965	1
Milwaukee Road	380-391	35632-35643	1453	6/1965-8/1965	12
Erie Lackawanna	2513-2527	35652-35666	1456	7/1965-9/1965	15
New York Central	2561-2569	35691-35699	1458	7/1965-9/1965	9
New York Central	2560	35700	1458	9/1965	1
Rock Island	225-238	35701-35714	1452	9/1965-10/1965	14
New York, New Haven & Hartford	2510-2525	35718-35733	1457	10/1965-11/1965	16
St. Louis-San Francisco Railway (Frisco)	824-831	35761-35768	1459	1/1966-2/1966	8
Pennsylvania	2649-2658	35773-35782	1463	11/1965-12/1965	10

Pennsylvania U25B #2655 was photographed here at the road's terminal in Enola, Pennsylvania, circa 1967. Note the GP9B behind the U-boat. Fred Byerly photo. American-Rails.com collection.

6* When outshopped in April, 1959 these U25B's were originally designated as the XP24 (Export Test Unit, 2400 Horsepower).

Both were sent back to GE's Erie, Pennsylvania plant in 1960, upgraded to 2,500 horsepower, and subsequently painted in a blue and cream livery.

They were ultimately never sold and remained at GE's plant.

** All built with the high, short hood. Acquired by the St. Louis-San Francisco Railway (Frisco) in December, 1961 becoming #804-807.

*** Featured high, short hoods.

**** #2501 featured a low nose while #2502 sported a high, short hood. Became Union Pacific #633 and #635 in July, 1962.

***** Both featured a high, short hood. Became Union Pacific #634 and #636 in July, 1962.

****** All built with a low nose. Acquired by the St. Louis-San Francisco Railway (Frisco) in July, 1963 becoming #812-815.

A trio of Erie Lackawanna U25B's, a little more than a year old, are stopped next to the depot in Binghamton, New York with a westbound freight in November, 1966. Author's collection.

Reception

When production had ended, GE had built some 478 U25B's (including the two initial demonstrators which never sold). While sales were not jaw-dropping they were nevertheless solid for an entry-level model.

The U25B propelled GE into the locomotive market and future U-boat models continued to witness strong sales.

For Alco, of course, the U25B marked the beginning of the end. GE had done its homework and ever reactionary, Alco soon slipped into third place. It exited the market altogether in 1969.

Today, at least seven GE U25Bs remain preserved around the country; Louisville & Nashville #1616, Milwaukee Road #387-388, New Haven #2525, New York Central #2500 and #2510, and Southern Pacific #7508.