EMD SD40X

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EMD SD40X
Power type Diesel-electric
BuilderElectro-Motive Division
ModelSD40X
AAR wheel arr.C-C
UIC classificationCo'Co'
Gaugeft 8½ in (1435 mm)
Total weight420,000 lbs (190,5087954 kg)
Prime moverEMD 16-645
Engine type2 stroke diesel
AspirationTurbocharger
TransmissionDC generator
DC traction motors
Top speed74 mph
Power output3,000 hp (2.2 MW)
Locomotive brakesStraight air, dynamic braking
Train brakesWABCO 26L-air
CareerUnion Pacific Railroad


An EMD SD40X is an 6-axle diesel-electric locomotive built by General Motors Electro-Motive Division between 1964 and 1965. 9 examples of this locomotive were built for test purposes to test the new 645-series prime mover. After testing, eight were sold to the Union Pacific Railroad and one example to the Gulf, Mobile and Ohio Railroad. This locomotive is an experimental testbed for the production EMD SD40, but built on the shorter EMD SD35 frame. This locomotive was also known as an SD35X.

The designation SD40X was also given to an experimental version of the EMD SD50, also built by EMD on an SD40-2 frame. 4 examples of this SD40X were built in 1979 and were delivered to the Kansas City Southern as KCS 700-703.