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Locomotive Descriptions and Phases - EMD/GMD GP7, GP9

The GP7 marked EMD's first serious entry into the road switcher market in 1949. Although it was late to the party, with similar road switchers from ALCO, Baldwin and Fairbanks-Morse having been in production for several years by that point, it ultimately became the most successful of the bunch. Together with the GP9, it accounted for thousands of first-generation locomotives and was a common sight for much of the last half of the 20th Century, and the general design was retained up to the end of GP18 production in 1963.

The proven 567-series engine and swing-hanger "Blomberg" trucks were carried over from the streamlined F series, but in place of a structural carbody, the GP7 used a solid underframe with a narrow hood on top. The radiators were split into two sections (at the front and rear of the hood) and dynamic brakes (if present) occupied a raised "blister" in the center of the hood. The short hood or "nose" was the same height as the engine compartment, and although the hood was angular, the cab retained an arched roof similar to previous EMD switchers. The GP9 was an evolutionary change, with the biggest difference being an increase from 1,500 to 1,750 horsepower.

Many GP7's were retired by the 1980s, although some were rebuilt and continued in service. As the later 567C engine used in the GP9 was more easily upgraded with 645-series engine components, many rebuilt GP9's remained in service well into the 21st Century, even on class-1 railroads such as CN and CP.

Phases - GP7

These phases are based on those compiled by Scott Chatfield. I split Chatfield's original Phase 2 into four sub-phases based on minor details.

One detail I haven't been able to figure out is in regards to length. The overall length of the units is commonly listed as either 55' 11" or 56' 2" for the GP7, and 56' 2" for the GP9. The difference in length can be attributed to the coupler pockets, with the coupler extending either 23.5" or 25" from the pilot face, as the length over the underframe didn't change. However, it appears the change in length did not occur with the change in coupler pocket design from cast to welded early in GP9 production. I haven't been able to confirm when the change took place, and photo measurements I've taken of several GP7's all suggest a coupler-to-pilot distance of 25" (and therefore a length of 56' 2").

A singled order by MP used GP7 components inside a GP9 Phase 1a carbody, and these units are sometimes referred to as "Phase 4".

Phase 1 2a 2b 2c 2d 3
Dates 1949-10 -
1950-11
1950-06 -
1952-03
1952-03 -
1952-07
1952-07 -
1952-10
1952-10 -
1953-02
1953-03 -
1953-12
Dynamic brakes Not available Optional; 36" fan Optional; 48" fan
Box behind cab (conductor's side) No Yes
Fuel tank skirt Solid Slotted (units with 1200+ gallon fuel tank only)
Sloped pilot plates Yes No
Hood straps around engine compartment Full-height Top of hood only (dynamic brakes)
or absent (no dynamic brakes)
Engine room doors 86" (no dynamic brakes)
or 82" (under dynamic brake blister)
All 82"

Transition: Phase 3 GP7 to Phase 1a GP9

Very early in GP9 production, the coupler pocket and striker plate was changed from a curved, cast housing to a welded version with a flat angled plate on top.

The following detail changes were made to the carbody:

Additionally, the air reservoirs received a different pipe arrangement. The piping on the rear reservoir of the GP7 was an L shape on both sides, extending rearward then vertically behind the side skirt. On the GP9 this was changed to a horizontal pipe between the reservoirs on the left side, and a vertical pipe that went straight under the side skirt on the right side. (There were additional changes in the pipe routing above the level of the side skirt.) The air reservoirs were supported at the top by curved brackets on the GP9 rather than simple straps and bolts as on the GP7.

Phases - EMD GP9

Phase 1a 1b 2 3a 3b 3c
Coupler pocket and striker plate Cast Welded (appeared on late Phase 1a units)
Handrail stanchions Fabricated pipe Stamped sheetmetal
Hood louvers   Lower louvers removed from first 2 generator room doors (behind cab)
louvers added to 3rd engine room door
Fuel tank skirt Deep; fuel filler near rear Shallow; fuel filler at front
Battery box louvers (ahead of cab) Single large louver group 2 small louver groups
Radiator fans Four 36" fans Two 48" fans

Phases - GMD GP9

Although relatively few GP7's were built for Canadian railroads, several hundred GP9's were built by GMD, largely for CN and CP. While the phase details were generally the same as on US-built units, the order in which they changed was slightly different.

Phase 1a 1b 2a 2b 2c 3a 3b
Dates 1954-02 -
1955-04
1955-04 -
1956-06
1955-08 -
1956-07
1956-07 -
1957-12
1957-06 -
1958-03
1958-04 -
1959-11
1960-05 -
1963-08
Coupler pocket and striker plate Cast Welded (inconsistent)
Handrail stanchions Fabricated pipe Stamped sheetmetal
Hood louvers   Lower louvers removed from first 2 generator room doors (behind cab)
louvers added to 3rd engine room door
Cab sides Smooth Horizontal seam below window
Battery box louvers (ahead of cab) Single large louver group 2 small louver groups
Fuel tank skirt Deep; fuel filler near rear Shallow (if present);
fuel filler moved forward
Notched; fuel filler
at front (as on EMD GP18)
Radiator fans Four 36" fans Two 48" fans
Air reservoirs Crosswise, behind fuel tank Lengthwise, above fuel tank