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GE "U33B" Locomotives

Last revised: June 2, 2023

By: Adam Burns

The U36B was the final four-axle variant General Electric cataloged as part of its Universal line.  It was also the powerful B-B road-switcher any manufacturer ever offered, boasting an impressive 3,600 horsepower.

From a historical perspective, GE's early 7FDL prime mover is often underappreciated for its ruggedness and pure horsepower capability.

The U36B was a compact design at just over 60 feet in length, yet offered 600 more horsepower than any other model.

By comparison, Alco offered its C636 and Electro-Motive its SD45; both of which could also produce 3,600 horsepower. However, these models were C-C variants (six axles) and considerably longer (the C636 was nearly 70 feet in length and the SD45 over 65 feet).

From a sales perspective, the U36B was not a success.  However, its numbers were aided by Seaboard Coast Line's order, which totaled 108 examples of the 125 sold.  

By the 1970s, railroads were well aware of the advantages that six-motored, high-horsepower locomotives offered.  As a result, comparative four-axle models saw increasingly fewer orders.

Interestingly, the U36B did earn some distinction among train enthusiasts as the type chosen to power the all-new Auto Train of 1971.

The service was a privately-funded and managed operation.  Its trademark was allowing passengers to take their automobile with them when traveling from Virginia to Florida. 

The idea was initially successful although the Auto Train later foundered.  It was subsequently retained by Amtrak and remains a popular service today.


Seaboard Coast Line U36B #1776, in its Bicentennial colors, is seen here leading a long freight through Raleigh, North Carolina during the summer of 1971. Warren Calloway photo.


The U36B was a continuation of the earlier U33B with the first unit, Seaboard Coast Line #1748, rolling out of Erie, Pennsylvania in May, 1970.

GE made no fanfare of the upgraded model, which first began testing in October, 1967 as upgraded U33B variants. according to Greg McDonnell's book, "U-boats."

Interestingly, neither did the largest buyer of the model, Seaboard Coast Line.  The railroad numbering series for the U36B was simply a continuation of the U33B line.

As GE advanced its locomotive development, the U36B outwardly carried many of the same features of the first "Dash 7" designs. 

Most notable was the rear flared radiator which had first appeared on the U33B to handle the increased horsepower. Today, this feature remains a classic GE trademark. 


As GE's last 4-axle U-boat, the U36B sold poorly with just 125 units built by the time production had ended in December, 1974.

The Seaboard Coast Line purchased the most, 108, and the Auto-Train Corporation originally ordered another 17.  However, in an interesting twist, the company went bankrupt before the final four units were delivered.

As a result, what would have became Auto Train #4013-4016 sat on GE property for two years before Conrail expressed interest in the quartet in 1976.

The units became Conrail #2971-2974 and were delivered to the new upstart in September, 1976.  These locomotives carried particular noteworthiness as the first new power on the Conrail system.

The Seaboard Coast Line's 103 models remained in use through the CSX Transportation merger of the 1980s.  The company had mostly retired the fleet by the early 1990s and subsequently sold the units to various short lines.

Lastly, for more information about the U36B, data sheet information, and production totals please refer to the charts below.

Data Sheet and Specifications

Entered Production5/1970 (Seaboard Coast Line #1748)
Years Produced5/1970 - 12/1974
GE ClassU36B
Engine7FDL16 (16 cylinder)
Engine BuilderGeneral Electric
Length60' 2"
Height (Top Of Rail To Top Of Cab)14' 9"
Width9' 11"
Weight254,800 Lbs
Fuel Capacity3,000 Gallons
Air Compressor3CDC (Westinghouse)
Air Brake Schedule26NL (Westinghouse)
Truck TypeSwing Bolster, Drop-Side Equalizer (GSC) or Floating Bolster FB2 (GE)
Truck Wheelbase9' 4"
Wheel Size40"
Traction Motors752 (4), GE
Traction AlternatorGTA-11AC, GE
Auxiliary GeneratorGY27, GE
MU (Multiple-Unit)Yes
Dynamic BrakesOptional
Gear Ratio74:18
Tractive Effort (Starting)70,000 Lbs
Tractive Effort (Continuous)64,000 Lbs at 10.7 mph
Top Speed70 mph

Production Roster

Owner Road Number Serial Number Order Number Completion Date Quantity
Seaboard Coast Line1748-177737411-3744010005/1970-8/197030
Seaboard Coast Line1813**3743910008/19701
Seaboard Coast Line1778-181237774-3780810053/1971-8/197135
Seaboard Coast Line1776 (2nd)***3799910056/19711
Auto Train4000-4004*38031-38035100911/19715
Seaboard Coast Line1814-183438036-3805610089/1971-12/197121
Seaboard Coast Line1835-185538278-3829810121/1972-3/197221
Auto Train4005-4009*38744-38748148412/19725
Auto Train4010-4012*39845-3984714345/19743
Auto Train4013-4016****40064-40067143412/19744

*        Equipped with Blomberg trucks.

**       Original #1776.

***    Delivered in June, 1971 wearing a red, white and blue Bicentennial livery.

****    Built but never delivered.

***** Former Auto Train #4013-4016, acquired after the company went bankrupt.  These four units were Conrail's first new diesels.

All Seaboard Coast Line U36B's were equipped with Blomberg trucks.


  • Foster, Gerald. A Field Guide To Trains. New York: Houghton Mifflin, 1996.
  • Marre, Louis A. Diesel Locomotives: The First 50 Years, A Guide To Diesels Built Before 1972.  Milwaukee: Kalmbach Publishing Company, 1995.
  • 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.

A nice cab view of Seaboard Coast Line U36B #1776, wearing its Bicentennial colors, in Raleigh, North Carolina in 1971. Warren Calloway photo.

Today, at least one U36B is preserved, former Seaboard Coast Line #1776 (2nd) that originally wore Bicentennial colors upon its delivery in 1971.  Today it resides at the Lake Shore Railway Historical Society.

The unit had spent a great deal of time at the Massachusetts Call Volunteer Firefighters Association following retirement from CSX.

During this time the museum states that it served as "a rolling education/training unit for emergency services and police personnel across the eastern United States."

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