Locomotive Phases - EMD GP39X, GP49, GP50
These phases are based on the GP39X, GP49 and GP50 roster compiled by Robert Sarberenyi.
Transition: From GP40-2 to GP50
The most obvious difference between a late GP40-2 and an early GP50 is the taller radiator intakes on the GP50. However, despite many shared dimensions and an overlapping production run, the GP50 actually rode on a different underframe and had largely new sheetmetal above the walkway. The underframe on the GP50, although the same length as on the GP40-2, was about 1.5" taller and had different pipe and cable routing. Likewise, most of the hood was moved to the rear by about 7", necessitating a rear sill extension to walk around the end of the hood. The central hood door spacing and first hood door width were marginally narrowed, and the dynamic brake taper was redesigned. The changes to the middle and rear of the hood resulted in a notable lengthening of the front section of the hood (about 6"), with a larger inertial air intake on the left and more space between the cab and blower duct.
While the last GP40-2 was built after the last GP50, the GP40-2 retained its existing frame and hood over the entire production run and did not use the new frame or hood components introduced with the GP50. This is in contrast with the GP39X and the last order of GP39-2's, both of which used the hood design and frame of the GP49/GP50.
Phase 1a1: 1980.05 - 1980.09
- (Contemporary to GP40-2 Phase 2c1)
- Battery box covers: Bolted, no horizontal rib
- Blower duct: Flat, wide, two ribs, no raised walkway
- Exhaust silencer: Opening at rear
- Frame side sill: Narrow over air reservoirs, wide at ends
Phase 1a2: 1980.09 - 1981.06
- (Contemporary to GP40-2 Phase 2c2)
- Battery box covers: Horizontal rib added
Phase 2a: 1983.09
- Short hood: Bolted hatch added on top
- Blower duct: Angled, narrow, no ribs, raised walkway ("laundry chute")
- Exhaust silencer: Opening at front
- Frame side sill: Narrow over entire length
Phase 2b: 1985.04 - 1985.11
- (Contemporary to GP40-2 Phase 3)
- Battery box covers: Latched, lift-off tabs
- Some Phase 1 and all Phase 2 units used leaf springs instead of rubber pads for the truck secondary suspension.
- Phase 2a applies only to the first order of ARR GP49s.
- The last order of GP39-2's (MKT 360-379) used the frame and hood of the GP39X/GP49, as opposed to the Dash-2 frame and hood.