The EMD DD35A was a 5,000 hp (3,700 kW) diesel locomotive

Diesel locomotive

A diesel locomotive is a type of railroad locomotive in which the prime mover is a diesel engine, a reciprocating engine operating on the Diesel cycle as invented by Dr. Rudolf Diesel...

 of D-D wheel arrangement

Wheel arrangement

In rail transport, a wheel arrangement is a system of classifying the way in which wheels are distributed beneath a locomotive.. Several notations exist to describe the wheel assemblies of a locomotive by type, position, and connections, with the adopted notations varying by country...

 built by General Motors Electro-Motive Division exclusively for the Union Pacific Railroad

Union Pacific Railroad

The Union Pacific Railroad , headquartered in Omaha, Nebraska, is the largest railroad network in the United States. James R. Young is president, CEO and Chairman....

. They were a cab

Cab (locomotive)

The cab, crew compartment or driver's compartment of a locomotive is the part of the locomotive housing the train driver or engineer, the fireman or driver's assistant , and the controls necessary for the locomotive's operation....

-equipped variant of the previous, cabless booster (B unit

B unit

A "B" unit, in railroad terminology, is a locomotive unit which does not have a driving cab, or crew compartment, and must therefore be controlled from another, coupled locomotive with a driving cab . The term booster unit is also used. The concept was largely confined to North America...

) EMD DD35

EMD DD35

The EMD DD35 was a diesel-electric locomotive of D-D wheel arrangement built by General Motors Electro-Motive Division for the Union Pacific Railroad and Southern Pacific Railroad. In the early 1960s Union Pacific started asking for a 15,000 hp 3-unit locomotive set to replace the turbines...

 (sometimes erroneously called the 'DD35B'). Fifteen DD35A locomotives were built between May and July 1965; they were assigned road numbers 70 through 84. A further development of the 8 axle, twin-engined locomotive produced the final, best known type, the DDA40X

EMD DDA40X

The EMD DDA40X was a D-D diesel-electric locomotive built by the General Motors EMD division of La Grange, Illinois for the Union Pacific Railroad...

 "Centennial".

Like its cabless predecessor, the DD35A was essentially two EMD GP35

EMD GP35

An EMD GP35 is a 4-axle diesel locomotive built by General Motors Electro-Motive Division between July 1963 and December 1965 and by General Motors Diesel between May 1964 and January 1966. Power was provided by an EMD 567D3A 16-cylinder engine which generated .Many railroads traded in Alco and...

 locomotives on a common frame, riding on a pair of 4-axle Flexicoil trucks

Bogie

A bogie is a wheeled wagon or trolley. In mechanics terms, a bogie is a chassis or framework carrying wheels, attached to a vehicle. It can be fixed in place, as on a cargo truck, mounted on a swivel, as on a railway carriage/car or locomotive, or sprung as in the suspension of a caterpillar...

. The cab of a GP35 was fitted to the front end, requiring a longer frame than the DD35; the fuel tank beneath was lengthened, and the center pass-through walkway was offset a little to the rear because of the single cab. Another difference was that the DD35A was fitted with the new flared radiator section EMD was testing on its EMD 645

EMD 645

The EMD 645 family of diesel engines was designed and manufactured by the Electro-Motive Division of General Motors. Intended primarily for locomotive, marine and stationary engine use, one 16-cylinder version powered the 33-19 "Titan" prototype haul truck designed by GM's Terex...

-engined demonstrators (the prototype SD40

EMD SD40

The EMD SD40 is a 6-axle diesel locomotive built by General Motors Electro-Motive Division between January 1966 and August 1972.-Design:Like its predecessor in EMD's catalog, the SD35, the SD40 is a high-horsepower, six-motor freight locomotive....

 demonstrators).

The DD35s were initially quite unreliable; some of this was blamed on sand from the internal sandboxes getting in electrical gear, so new sandboxes were fitted on the walkways in 1969. The DD35s were among the last EMD road units to be built with DC generators and old-fashioned switchgear, which were more maintenance intensive than the later AC/DC equipment.

Once teething troubles had been overcome, the DD35s were reasonably successful, but they were less flexible than smaller units and thus with the economic downturn of the early 1980s they were withdrawn from service. All were gone by 1981. In their final months of service they operated around Salt Lake City, Utah

Salt Lake City, Utah

Salt Lake City is the capital and the most populous city of the U.S. state of Utah. The name of the city is often shortened to Salt Lake or SLC. With a population of 186,440 as of the 2010 Census, the city lies in the Salt Lake City metropolitan area, which has a total population of 1,124,197...

. No examples of this type remain.

Original Buyers

Owner	Quantity	Numbers
Union Pacific Railroad	15	70-84