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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.


Phase 1a1 1a2 1a3 1a4 1b 2a1 2a2 2b 2c 3
Dates 1965-11 -
1966-03 1966-04 -
1967-06 -
1967-07 -
1967-09 -
1967-09 -
1968-06 -
1971-04 -
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
Phase 1a1 1a2 1a3 1a4 1b 2a1 2a2 2b 2c 3

Model variations

Other details

 Copyright © Michael Eby - Last updated 2018-10-31