TheEMD Dash 2is a line ofdiesel-electric locomotives introduced byGeneral Motors'Electro-Motive Division (EMD) on January 1, 1972.[1] Designations of these models were those of the former models with "-2" added (e.g., the SD40 was replaced by the SD40-2). They retained the basic specifications of the earlier models in terms of power output and most other features, but introduced a number of improvements to the locomotives' internal systems, specifically the electrical systems and the trucks of the locomotives. 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 theDDA40X.
Minor externally visible changes common across the whole line include the following:
The Dash 2 line was highly successful. The models offered included the following:
In addition, many other earlier locomotives were rebuilt to Dash 2 standards by numerous locomotive rebuilders and railroad shops.
Among the most popular rebuilds areSD40,SD45,SD40T-2 andSD45T-2 into the functional equivalent of anSD40-2, although the frame, carbody and trucks remain the same as on the "donor" locomotive. In many cases, the rebuilds are identified as, for example, an SD40-3 or an SD40M-2, or an equivalent distinguishing identification. In some cases, the locomotive is identified simply as an SD40-2, although it is clear through physical examination that it is a rebuild. Once so rebuilt, the locomotive enters the owner's fleet as if it were a true SD40-2, arguably the most versatile and reliable diesel-electric locomotive of its time, if not all-time.[according to whom?]
Although not as popular as the SD40-2 rebuilds,GP40s,GP39/SD39s andGP38/SD38s have also been rebuilt to the equivalent ofGP40-2s,GP39-2/SD39-2s andGP38-2/SD38-2s, so significant were the reliability and serviceability advantages of the Dash 2 line.
Models subsequent to theDash 2 line, for exampleSD50,SD60 andSD70, et al., incorporatedDash 2 improvements at the outset. In this context, the model suffix-2 is only applicable to the40 Series, although-2 has been applied to certain variations of the later models.