On January 1, 1972, General Motors' Electro-Motive Division (EMD) introduced its new Dash 2 line of diesel-electric locomotives. All designations of these new models were those of the former models with "-2" added (e.g., the SD40 was replaced by the SD40-2). They all retained the basic specifications of the earlier models in terms of power output and most other features, but introduced a large number of improvements to the locomotives' internal systems, specifically the electrical systems. These were intended to improve availability, efficiency, and ease of maintenance. One major improvement was a modularized electrical control cabinet, allowing maintenance by unit replacement and the use of common parts. These concepts were first tested on 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...

.

Changes

Minor externally visible changes common across the whole line include the following:

• Modified 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...
  
   with damping struts. Four-axle trucks have damping struts on two diagonally opposite corners. Six-axle trucks have them on the center axle.
• Engine water level sight glass
  Sight glass
  A sight glass or water gauge is a transparent tube through which the operator of a tank or boiler can observe the level of liquid contained within.-Liquid in tanks:...
  
   on the rear upper right-hand side of the long hood
  Long hood
  The long hood of a hood unit-style diesel locomotive is, as the name implies, the longer of the two hoods on a locomotive.-Equipment:...
  
  .
• Battery boxes in front of the cab have bolted down covers, rather than hinged.
• Equipped with both high and low positions for rear classification lights, one set being blanked.
• Cab roof extends slightly beyond the cab rear.

Models

The Dash 2 line was highly successful. The models offered included the following:

• F40PH
  EMD F40PH
  -Amtrak NPCU Conversions:In later years, as Amtrak's F40PH fleet was being replaced by the newer GE Genesis-series locomotives, Amtrak converted a number of the retired units—generally ones with major mechanical problems limiting their value in the resale or lease marketplace—into "Non-Power...
  
  
• GP38-2
  EMD GP38-2
  An EMD GP38-2 is a four-axle diesel-electric locomotive of the road switcher type built by General Motors Electro-Motive Division. Part of the EMD Dash 2 line, the GP38-2 was an upgraded version of the earlier GP38...
  
  
• GP38-2W
• GP39-2
  EMD GP39-2
  An EMD GP39-2 is a 4-axle diesel locomotive built by General Motors Electro-Motive Division between 1974 and 1984. 239 examples of this locomotive were built for American railroads. Part of the EMD Dash 2 line, the GP39-2 was an upgraded GP39...
  
  
• GP40-2
  EMD GP40-2
  An EMD GP40-2 is a 4-axle diesel road switcher locomotive built by General Motors Electro-Motive Division as part of its Dash 2 line between April 1972 and December 1986. Power was provided by an EMD 645E3 16-cylinder engine which generated 3000 horsepower .- Production :Standard GP40-2 production...
  
  
• GP40-2L(W)
• GP40-2W
• GP40P-2
• SD38-2
  EMD SD38-2
  An EMD SD38-2 is a six-axle diesel locomotive built by General Motors Electro-Motive Division from 1972 to 1979. EMD built 83 of these medium road-switchers, which were used in both yard and mainline roles. Part of the EMD Dash 2 line, the SD38-2 was an upgraded SD38 with modular electronic...
  
  
• SD40-2
  EMD SD40-2
  The EMD SD40-2 is a C-C locomotive produced by EMD from 1972 to 1989.The SD40-2 was first introduced in January 1972 as the mid-range offering in EMD's six-axle "Dash-2" series, competing against the GE U30C and the MLW M630...
  
  
• SD40-2F
• SD40-2W
• SD40T-2
  EMD SD40T-2
  An EMD SD40T-2 is a 6-axle diesel locomotive built by General Motors Electro-Motive Division. Power is provided by a 16-cylinder EMD 645E3 diesel engine capable of producing . The Southern Pacific's locomotive features a fuel tank and is long. The Rio Grande's locomotive features a smaller fuel...
  
  
• SD40-2S
• SD45-2
  EMD SD45-2
  An EMD SD45-2 is a 6-axle diesel locomotive built by General Motors Electro-Motive Division beginning in 1972. Power was provided by an EMD 645E3 20-cylinder engine which generated . Part of the EMD Dash 2 line, the SD45-2 was an upgraded SD45.The main spotting difference between an SD45 and an...
  
  
• SD45T-2
  EMD SD45T-2
  The EMD SD45T-2 is a 6-axle diesel locomotive conceived in early 1972 by EMD at the request of the Southern Pacific Railroad. Like the similar SD40T-2, this locomotive model is nicknamed a "tunnel motor". 247 of this model were built from February 1972 to June 1975. Out of the total, 84 units were...
  
  

Rebuilds

In addition, many other earlier locomotives were rebuilt to Dash 2 standards by numerous locomotive rebuilders and railroad shops.