Identification
The GP7, GP9 and GP18 locomotives share a similar car-body that evolved over time. Most GP7s had three sets of ventilation grills under the cab (where the GP9 only had one), and two pair of grills at the end of the long hood (where only the pair nearest the end was retained on the GP9). However, some late GP7s were built with car-bodies that were identical to early GP9s. Early GP7s had a solid skirt above the fuel tank, while late GP7s and early GP9s had access holes in the skirt (see photo of Illinois Terminal 1605, top left). Many railroads later removed most of the skirt to improve access and inspection.
Locomotives could be built with the engineer’s control stand installed for either the long hood, or the short hood designated as the front. Two control stands for either direction running was also an option, but one end would still be designated as the front for maintenance purposes. The GP7 was also available with or without dynamic brakes, and a steam generator installed in the short hood was also an option. In the latter case the 1,600 US gallons (6,100 l; 1,300 imp gal) fuel tank was divided, with half for diesel fuel, and half for boiler water. One option available for locomotives without dynamic brakes, was to remove the two 22.5 in × 102 in (571.5 mm × 2,590.8 mm) air reservoir tanks from under the frame, and replace them with four 12 in × 150.25 in (304.80 mm × 3,816.35 mm) tanks that were installed on the roof of the locomotive, above the prime mover. These “torpedo tubes” as they were nicknamed, enabled the fuel and water tanks to be increased to 1,100 US gallons (4,200 l; 920 imp gal) each, although some railroads opted for roof-mounted air tanks and 2,200 US gallons (8,300 l; 1,800 imp gal) fuel tanks on their freight ‘Geeps’.
Read more about this topic: EMD GP7