GP7/GP9

[Christian_H]

Hi,I´m Christian from Germany,

what are the differences between GP7 and GP9?

[jrbernier]

The GP7 was a 1500 hp engine produced by EMD in the early 50’s. It was replaced in the EMD catalog in 1954 by the 1750 hp GP9. A GP7 has 2 full rows of louvers at the rear of the carbody, and 3 single louvers on the battery boxes under the cab. GP9’s have just one single louver on the rear of the carbody, and a single louver on the battery box. Features like S/G, D/B, fuel tank size & roof mounted air tanks are all optional feature that can be on either model.

Jim

[Beach_Bill]

GP7s had production from October 1949 though May of 1954 and had a 567B 16-cylinder engine producing 1500 hp. GP9s were produced from January of 1954 through December of 1959 and had a 567C engine which produced 1750 hp. There were 2610 GP7s and 3436 GP9s built.

For identification, the GP7 has three louvers below the cab and two vertical rows of louvers under the radiator shutters at the far end of the long hood. The presence or absence of the dynamic brake blister atop the hood tells nothing about which style it is. Those louvers below the cab are the quickest identifier to distinguish between the two.

(Source: The Second Diesel Spotter’s Guide by Jerry A. Pinkepank; Kalmbach books).

Bill

[Railway_Man]

Hi,I´m Christian from Germany,

what are the differences between GP7 and GP9?

Others have cited the external differences. The internal differences were substantial and the ones that mattered to railroads.

1. GP7s used the 16-567B engine, rated at 1,500 hp. The B crankcase had cooling water leakage problems at the top and bottom of the cylinder liner. As the engine expanded and contracted with change in operating temperature, the seals would not respond at the same rate and water leaks occurred. The C crankcase eliminated the rubber seals where the leaks occurred and replaced them with water jumpers that had much less problem with leakage. Many B crankcases were upgraded to BC crankcases, because it was possible to replace the lower seal with the C-style arrangement without heavy modification to the crankcase. C engines also had better pistons, liners, heads, and valves, and were all-around stronger and more durable.

2. The 250-hp increase wasn’t very meaningful, and was achieved by increasing the maximum governed speed from 800 to 835 rpm. Many users reset the governors to reduce the speed back to 800 rpm to increase engine longevity.

3. Traction motors were upgraded from D27 to D37 model, primarily an insulation improvement that enabled a little bit longer short-time rating but more importantly much longer life and less insulation breakdown, meaning less issues with grounding as the motor aged.

4. Radiator cores were upgraded and were larger. Late-series GP9s used two 48" cooling fans instead of the four 36" fans in the GP7 and early GP9.

5. The electrical control system was completely revamped and improved, with better wheel-slip detection and control system, better and longer-lasting power contactors, and better relays. The GP9 introduced point-potential dynamic brake control instead of the awful field

[SSW9389]

Beach Bill you left off the Canadian and Mexican GP7s and GP9s. Plus DSG II does not count the GP9s exported to Brazil, Peru, and Venezuela.

Also GP9s were built in Canada by GMDD through the summer of 1963.

Ed

GP7s had production from October 1949 though May of 1954 and had a 567B 16-cylinder engine producing 1500 hp. GP9s were produced from January of 1954 through December of 1959 and had a 567C engine which produced 1750 hp. There were 2610 GP7s and 3436 GP9s built.

For identification, the GP7 has three louvers below the cab and two vertical rows of louvers under the radiator shutters at the far end of the long hood. The presence or absence of the dynamic brake blister atop the hood tells nothing about which style it is. Those louvers below the cab are the quickest identifier to distinguish between the two.

(Source: The Second Diesel Spotter’s Guide by Jerry A. Pinkepank; Kalmbach books).

Bill

[SSW9389]

My counts on the Geeps:

GP7 2729 built 10/49-10/58

GP7B 5 built 3-4/53

GP9 4107 built 1/54-8/63

GP9B 165 built 2/54-12/59

And I used the www not the DSG2.

[markpierce]

Beach Bill you left off the Canadian and Mexican GP7s and GP9s. Plus DSG II does not count the GP9s exported to Brazil, Peru, and Venazuela.

Also GP9s were built in Canada by GMDD through the summer of 1963.

Ed

Too bad the Cotton Belt had only a singleton GP7. At least it started out with a Daylight paint scheme.

Mark

[SSW9389]

Very true and thanks Mark. Here is Cotton Belt GP7 #304 working her last Summer on the Cotton Belt in Commerce, TEXAS. She was sold in November 1972 and ended up going through the Paducah Rebuild program. Terry A. Kirkland photo.

Ed

Beach Bill you left off the Canadian and Mexican GP7s and GP9s. Plus DSG II does not count the GP9s exported to Brazil, Peru, and Venazuela.

Also GP9s were built in Canada by GMDD through the summer of 1963.

Ed

Too bad the Cotton Belt had only a singleton GP7. At least it started out with a Daylight paint scheme.

Mark

[SSW9389]

It took some serious time to verify the GP7 roster. The five units not in DSG2 are explained in the discussion section. You can even find out about that GP7 built in October 1958. And about the US Army GP7 that found its way to Cuba and then went to the USSR.

http://en.wikipedia.org/wiki/EMD_GP7

The GP9 roster is not done yet, but will take longer because there are more units to check.

http://en.wikipedia.org/wiki/EMD_GP9

These two Wikipedia pages provide some of the basic information about these two early EMD/GMDD Geeps.

Ed