EMD Dash 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.

One major improvement was a modularized electrical control cabinet, allowing maintenance by unit replacement and the use of common parts.

Among the most popular rebuilds are SD40, SD45, SD40T-2 and SD45T-2 into the functional equivalent of an SD40-2, although the frame, carbody and trucks remain the same as on the "donor" locomotive.

In some cases, the locomotive is identified simply as an SD40-2, although it is clear through physical examination that it is a rebuild.

Although not as popular as the SD40-2 rebuilds, GP40s, GP39/SD39s and GP38/SD38s have also been rebuilt to the equivalent of GP40-2s, GP39-2/SD39-2s and GP38-2/SD38-2s, so significant were the reliability and serviceability advantages of the Dash 2 line.