|AAR wheel arr.||C-C|
|Gauge||4 ft 8½ in (1435 mm)|
|Total weight||420,000 lbs (190,5087954 kg)|
|Prime mover||EMD 16-645|
|Engine type||2 stroke diesel|
DC traction motors
|Top speed||74 mph|
|Power output||3,000 hp (2.2 MW)|
|Locomotive brakes||Straight air, dynamic braking|
|Train brakes||WABCO 26L-air|
|Career||Union 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.
|Six-axle road power:||SD7 · SD9 · SD18 · SD24 · SD28 · SD35 · SDP35 · SD38 · SD38AC · SD38-2 · SD39 · SDL39 · SD40 · SD40X · SD40A · SD40-2 · SD40-2W · SD40T-2 · SD40-2S · SDP40 · SD45 · SD45X · SD45-2 · SD45T-2 · SDP45 · SD50 · SD60 · SD70 · SD70M · SD70MAC · SD70M-2 · SD70ACe · SD75M · SD75I · SD80MAC · SD90MAC|
|Eight-axle road power:||DD35 · DD35A · DDA40X · DDM45|
|See also: List of EMD locomotives|