EMD SD40-2 - Appearance and Spotting Features

Appearance and Spotting Features

As the SD38, SD39, SD40, and SD45 shared a common frame, so too did the SD38-2, SD40-2, and SD45-2. It was 3 ft (0.91 m) longer than the previous models, giving a length of 68 ft 10 in (20.98 m) over the coupler pulling faces. The SD38-2 and SD40-2 shared the same basic superstructure, since they used the same 16-645E3 engine (in naturally aspirated and turbocharged form respectively); the long hood was 18 inches (46 cm) longer than the SD38 and SD40, but since the increase in frame length was even greater, the SD38-2 and SD40-2 had even larger front and rear "porches" than the earlier models. These empty areas at front and rear are spotting features to identify the Dash 2 models of both units. The SD40-2 can be distinguished from the SD38-2 by its three roof-mounted radiator fans instead of two, and a single large exhaust stack instead of two smaller stacks.

The increase in the frame length between the preceding 40 Series and the 40-2 Series six-axle locomotives was made to accommodate the new HT-C truck design, in which the traction motors all face the same direction, making the trucks longer. After a series of derailments involving Amtrak SDP40F units that were equipped with "hollow bolster" HT-C trucks, applied only to the SDP40F, Conrail ordered the SD40-2 units and several orders of SD50s with the older Flexicoil trucks, but the HT-C truck was vindicated and it ultimately went under most 40 Series, 50 Series and 60 Series six-axle locomotives, and this truck is still found under many remanufactured locomotives.

As of 2008 some SD45 units have been modified by replacing their 20 cylinder engine with the 16 cylinder removed from scrapped SD40-2 units; this was common on Union Pacific and possibly other railroads. In many cases these are identified by the owner as SD40-3, SD40M-2 or some such. Confusingly, what appears to be an SD45 is labeled as an SD40-2. Older SD40-2 units used in low-power modes such as yard switching or hump service have been de-turbocharged, resulting in the mechanical equivalent of a SD38-2. Units so modified may or may not be re-labeled.

There are several variations of the SD40-2. Such as the SD40T-2s (T for tunnel motor) bought by fallen flags: Southern Pacific, and Denver and Rio Grande Western; now operated by the Union Pacific Railroad. There is the SD40-2W (W for the 4-Window Safety Cab) bought and operated by the Canadian National railway. There were high-nosed versions of the SD40-2 bought by fallen flags: Norfolk & Western, & Southern Railway. These units are now operated by the Norfolk Southern Railway (Resulting merger of N&W and The Southern Railway). There are even some narrow gauge versions around the world called BB40-2's.

Three cabless SD40-2Bs were also rebuilt from standard SD40-2s by the Burlington Northern Railroad in the early 1980s. The units had been in collisions and it was decided that it was more economical to rebuild them without cabs. Canadian Pacific also owns a few SD40-2Bs. These were created by welding metal plates over the cab windows of many of its ex-Norfolk Southern and some of its original SD40-2s.

By late 1978 railroads had the option to purchase roller bearing journal boxes later seen on the EMD SD50 and EMD SD60 models. In general, all North American diesel-electric road locomotives have roller bearings on all wheels, but not necessarily the same wheel bearing cover style on all wheels, due largely to supply constraints.