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UP DD35A 83.jpg
A Union Pacific DD35A and DD35 back to back at Laramie, Wyoming.
Type and origin
Power type Diesel-electric
Builder General Motors Electro-Motive Division (EMD)
Build date 1965
AAR wheel arr. D-D
Gauge 4 ft 8 12 in (1,435 mm)
Wheelbase Between truck centers:
65 ft 0 in (19.81 m)
Truck wheelbase:
17 ft 1 12 in (5.22 m)
Length 88 ft 2 in (26.87 m)
Width 10 ft 4 in (3.15 m)
Height cab roof: 14 ft 11 38 in (4.56 m)
overall: 16 ft 4 in (4.98 m)
Loco weight 519,353 lb (235,575 kg)
Fuel capacity 8,230 US gal (31,200 l; 6,850 imp gal)
Prime mover Dual EMD 16-567D3A
Engine type V16 diesel
Aspiration turbocharged
Cylinders 16
Safety systems Leslie Supertyfon model S5TRRO or S3LR horns
Performance figures
Power output 5,000 hp (3,730 kW)
Operators Union Pacific
Numbers 70 – 84
Disposition All scrapped

The EMD DD35A was a 5,000 hp (3,730 kW) diesel-electric locomotive of D-D wheel arrangement built by General Motors Electro-Motive Division exclusively for the Union Pacific Railroad. They were a cab-equipped variant of the previous, cabless booster (B unit) EMD DD35 (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 "Centennial".

Like its cabless predecessor, the DD35A was essentially two EMD GP35 locomotives on a common frame, riding on a pair of 4-axle Flexicoil trucks. 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-engined demonstrators (the prototype SD40 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 retired by 1981, and scrapped by July 1982. In their final months of service they operated around Salt Lake City, Utah. No examples of this type remain.

Original Buyers[edit]

Owner Quantity Numbers
Union Pacific Railroad 15 70-84