Locomotive Phases - EMD GP38, GP39, GP40
These phases are based directly on the GP38, GP39 and GP40 rosters compiled by David Thompson, with additional details from my own observations.
Transition: From Phase 2 GP35 to GP38/GP40
The chief mechanical difference between the GP35 and GP40 was the introduction of the more powerful 645-series engine, which necessitated a larger radiator section with three 48" fans in place of the one 36" and two 48" fans on the GP35. The lengthened hood required a 3' longer frame, increasing overall length from 56' 2" to 59' 2". The rear truck was moved 1' inward from the rear pilot face, making it symmetrical with the front truck and resulting in 34' truck centers (compared to 32' on the GP35). The longer frame allowed for a longer fuel tank, which increased in capacity to 3,600 gallons, although smaller sizes were also used. The walkway side frame was thicker above the air reservoirs than on the late GP35, but narrower than on the early GP35.
On the hood, the dynamic brake fan and intakes were moved rearward, and the taper of the dynamic brake hatch was made steeper at the rear than the front. Aside from this and the longer radiator section, the cab and hood were almost identical between the late GP35 and early GP40.
As on the GP28 (the non-turbocharged version of the GP35), the GP38 and GP39 used the same hood design as the GP40, but incorporated shorter radiator intakes with only two 48" fans.
|Cab sub-base doors||Smooth||Ribs on conductor's side||Ribs on both sides||Ribs made full-width (rather than ending before door edges)|
|Fans||Flat center cap||Open-top|
|MU receptacle housing||Short, wide, angled side||Tall, narrow, angled bottom (appeared on some late Phase 1 units)|
|End plates||Small tabs at bottom steps, end plates do not extend below steps||Angled extensions at bottom steps, end plate extends to bottom of pilot||No extensions at bottom steps (as on Dash-2 units)|
|Footboards||Flat plate on side extending behind pilot end plate (as on GP35)||Beveled plate on side flush with pilot end plate (as on Dash-2 units)|
|Fuel tank supports||Triangular brace||Pentagonal brace (rectangle with angled corner) additional plates bolted to underframe (absent with smaller fuel tanks)|
ECAFBElectrical cabinet air filter box, located on the left behind the cab
|No (unless subsequently added)||Yes|
|Short hood grabirons||Top-mounted, straight||Bottom-mounted, U-shaped (appeared prior to 1968-02 on LN units)|
|Radiator intake subscreen||Diamond mesh||Square wire grid|
|Blower duct||Flat||Two horizontal ribs|
|Front taper on dynamic brake housing||Short, angled||Longer, nearly straight|
|Handrail stanchions||Uneven spacing (closer at rear), bottoms not lined up||Even 48" spacing, bottoms lined up|
- Due to small production numbers, all GP39's have Phase 2b spotting features.
- Standard fan arrangement used tall radiator fans and a lower dynamic brake fan. Some units had lowered radiator fans, or dynamic brake fan raised on a rim.
- Multiple fuel tank sizes available: 1700, 2600, 3000, 3200 and 3600-gallon capacities.
- Sanding nozzle routing varied, either under or through brake beams.
- ECAFB was retrofitted to many earlier units.