EMD DDA40X

Specifications
Specifications
Configuration:;
• AAR	D-D
• UIC	Do'Do'
Gauge	4 ft 8+1⁄2 in (1,435 mm)
Trucks	2 × 8 wheel Flexcoil
Wheel diameter	40 in (1,016 mm)
Minimum curve	57°
Wheelbase:
• Engine	82 ft 1+1⁄2 in (25.03 m)
• Truck	17 ft 1 in (5.21 m)
Length:;
• Over couplers	98 ft 5 in (30.00 m)
Width	10 ft 3 in (3.12 m)
Height	17 ft 3+1⁄2 in (5.27 m)
Empty weight	521,980 lb (236,766 kg; 261 short tons; 237 t)
Service weight	545,453 lb (247,413 kg; 273 short tons; 247 t)
Fuel type	Diesel fuel
Fuel capacity	8,200 US gal (31,000 L; 6,800 imp gal)
Lubricant cap.	610 US gal (2,300 L; 510 imp gal)
Coolant cap.	600 US gal (2,300 L; 500 imp gal)
Sandbox cap.	53 cu ft (1.5 m3)
Prime mover	2 × 16-645 E3A
Engine type	2-stroke diesel
Aspiration	Turbocharged
Displacement	10,320 cu in (169,100 cm3)
Alternator	2 × Delco A8102
Generator	2 × GM - AR12
Traction motors	8 × GM - D77
Gear ratio	59:18
Train brakes	Westinghouse 26L air brakes and extended range dynamic braking
Safety systems	Leslie Supertyfon model S-5T-RF or S3LR horns, US&S Type 'EL' Cab Signals (6936 equipped with US&S MicroCab ATC & CCS)
Couplers	Type 'E'

Type and origin
Type and origin
Power type	Diesel–electric
Builder	General Motors Electro-Motive Division (EMD)
Order number	7134-1 – 7134-25; 7198-1 – 7198-22;
Serial number	34526–34550; 35499–35520;
Build date	January 1969 – September 1971
Total produced	47

EMD DDA40X
EMD DDA40X
	Union Pacific 6933, with another DDA40X and a GP30, hauls a TOFC train through Riverside, California. in March 1979
Power type
Type and origin
Power type	Diesel–electric
Builder	General Motors Electro-Motive Division (EMD)
Order number	7134-1 – 7134-25; 7198-1 – 7198-22;
Serial number	34526–34550; 35499–35520;
Build date	January 1969 – September 1971
Total produced	47
Configuration:;
Specifications
Configuration:;
• AAR	D-D
• UIC	Do'Do'
Gauge	4 ft 8+1⁄2 in (1,435 mm)
Trucks	2 × 8 wheel Flexcoil
Wheel diameter	40 in (1,016 mm)
Minimum curve	57°
Wheelbase:
• Engine	82 ft 1+1⁄2 in (25.03 m)
• Truck	17 ft 1 in (5.21 m)
Length:;
• Over couplers	98 ft 5 in (30.00 m)
Width	10 ft 3 in (3.12 m)
Height	17 ft 3+1⁄2 in (5.27 m)
Empty weight	521,980 lb (236,766 kg; 261 short tons; 237 t)
Service weight	545,453 lb (247,413 kg; 273 short tons; 247 t)
Fuel type	Diesel fuel
Fuel capacity	8,200 US gal (31,000 L; 6,800 imp gal)
Lubricant cap.	610 US gal (2,300 L; 510 imp gal)
Coolant cap.	600 US gal (2,300 L; 500 imp gal)
Sandbox cap.	53 cu ft (1.5 m3)
Prime mover	2 × 16-645 E3A
Engine type	2-stroke diesel
Aspiration	Turbocharged
Displacement	10,320 cu in (169,100 cm3)
Alternator	2 × Delco A8102
Generator	2 × GM - AR12
Traction motors	8 × GM - D77
Gear ratio	59:18
Train brakes	Westinghouse 26L air brakes and extended range dynamic braking
Safety systems	Leslie Supertyfon model S-5T-RF or S3LR horns, US&S Type 'EL' Cab Signals (6936 equipped with US&S MicroCab ATC & CCS)
Couplers	Type 'E'
Maximum speed
Performance figures
Maximum speed	80–90 mph (129–145 km/h)
Power output	6,600 hp (4,922 kW)
Tractive effort:;
• Starting	113,940 lbf (506,830 N) at 25%
• Continuous	103,000 lbf (458,167 N) at 12 mph (19 km/h)
Operators
Career
Operators	Union Pacific
Number in class	47
Numbers	6900 – 6946
Nicknames	"Centennial"
Delivered	6900-6924 April – December 1969; 6925-6946 June 1970 – September 1971;
Preserved	12 in museums (1 operational), 1 pending disposition
Disposition	34 scrapped

The EMD DDA40X is a 6,600 hp (4,922 kW) D-D locomotive, built by EMD from 1969 to 1971, exclusively for the Union Pacific Railroad. It is the most powerful diesel–electric locomotive model ever built on a single frame, having two 16-645E3A diesel prime movers. Union Pacific has marked DD40X on the cab exteriors, while EMD literature inconsistently refers to this model as either DD-40X or DDA40X.

UP's DDA40X locomotives were the culmination of the company's experiments with extremely powerful locomotives that began with its gas turbine–electric locomotives and DD35s. For manufacturer EMD, the construction of the world's most powerful single frame locomotive was a sign of the company's dominance of the North American diesel locomotive market, with only GE Transportation an equal competitor. The DDA40X also pioneered a number of new technologies that would go on to be incorporated in future EMD designs.

UP did not continue with exceptionally powerful locomotives like the DDA40X built on single frames, instead moving toward distributed power using smaller locomotives closer to 4,000 hp (3,000 kW). All DDA40X locomotives were retired between 1984 and 1986; several of them survive. Union Pacific 6936 operated as a member of the Union Pacific Heritage Fleet until 2022, when it was announced it would be donated to the Railroading Heritage of Midwest America.