Conrail's GP-9 "M's"

[NJT4272]

OK........ Here's a good one:

I've tried to find the answer, but I can't seem to find it. Apparently, a good number of Conrail's inherited GP-9's went through some sort of rebuild or modification process around 1977 and emerged as GP-9m's. The one's in particular that I'm interested in are the one's that retained their high, short hoods but received an interesting, box-shaped addition to the tops of their long hoods just forward of the dynamic brake resistor blister.

What I'm trying to deduce is what was the purpose of that box on the top of the long hood? As a case study, I offer former PRR GP-9 #7000, owned by the United Railroad Historical Society of New Jersey and in use on the Cape May Seashore Lines out of Tuckahoe, NJ. She began life as PRR 7000, the Pennsy's first GP-9. She retained her same number through Penn Central, Conrail, and ultimately New Jersey Transit.

In this picture from 1966, we see her in her original PRR dress without the box. In this photo from 1974, Penn Central livery and still no box. In 1978, Conrail now owns her and there's that box. In 1997, her service with NJ Transit is over and she's about to be restored to her PRR appearance, and it appears that box has been removed. Today, wearing her original PRR dress, the box is gone.

So what was in that box? Why did Conrail add it, and was it so insignificant that its possible to remove it without consequence to a still-functioning locomotive?

[Backshophoss]

This might be a "wild guess",believe it to be a "paper filter box" for engine air intake replacing "oil bath" type air filters.
The swap out of "oil bath" filters started with the ICRR's rebuilding program at Paducah Ky shops,rebuilding GP-7's-GP-9's
into "GP-10's"

[scharnhorst]

It is a paper filter box these were a bit easier to maintain and replace compared to the original filters from what I understand.
Parker makes the filters:
http://www.camfilfarrrailroad.com/

[lvrr325]

Conrail sent GP7s and GP9s to multiple rebuilders; the Rock Island did some, I believe the IC did some, and Morrisen-Knudsen or another third party may have done another group. So some came back chop nose and some didn't, depending on who rebuilt them. Most got a paper air filter and had dynamic braking removed.

[scharnhorst]

Rebuilders working on Conrail GP8 units (Ex GP9's) were as follows:
Illinois Central Gulf #'s 5400-5413 , 5429 & 5430
Rock Island Railroad #'s 5431-5449
Morrisen-Knudsen #'s 5450-5462

If you want a complete brake down as to what railroads these units came off of and the day date and month of there rebuild I can post it on request along with the day date and year each unit was retired.
Info is from Conrail Motive Power Review Vol 1 by Gordon Lioyd, Jr. and Louis A. Marre

[RSD15]

Rebuilders working on Conrail GP8 units (Ex GP9's) were as follows:
Illinois Central Gulf #'s 5400-5413 , 5429 & 5430
Rock Island Railroad #'s 5431-5449
Morrisen-Knudsen #'s 5450-5462

I have always thought that GP7s became GP8s and GP9s became GP10s, is that wrong?

[charlie6017]

You are correct, RSD!

[scharnhorst]

Rebuilders working on Conrail GP8 units (Ex GP9's) were as follows:
Illinois Central Gulf #'s 5400-5413 , 5429 & 5430
Rock Island Railroad #'s 5431-5449
Morrisen-Knudsen #'s 5450-5462

I have always thought that GP7s became GP8s and GP9s became GP10s, is that wrong?

I do have this info on Conrail's fleet as well. In 1992 Conrail had a total of 75 GP10 units rebuilt from GP9's the fleet as it stands was gone by 1997
7513-7529 were rebuilt by MK
7530, 7531, 7533-7535, 7537 were rebuilt by PNC
7545-7597 were rebuilt by ICG
All units were a Mix of PRR and NYC GP9's

Units 7572-7575 and 7582-7597 were equipped to operate as mother units for four motor trailers (SLUGS aka MT-4)
Units 7519, 7530-7533, 7550, 7551 equipped with front snow plows only
7552, 7554, 7555, 7558, and 7559 were equipped with plows on both ends


Info from CONRAIL The Final Years 1992-1997 by Paul K. Withers

[green_elite_cab]

GP9 7000 never got rebuilt into a GP10. I suspect they just blanked over the dynamic brakes, rather than rebuilt the unit all the way. I was under the impression that some sort of air-filter modifications were often installed in that location.

[ex Budd man]

At Septa we had two Geeps, 7019 & 7028, one in Conrail blue and the other in gray. They both were renumbered and repained in Septa's dark blue before becoming trade fodder for the Rebublic RL-!000 POS.

[lvrr325]

Conrail also overhauled quite a few units on their own, including GP7s and GP9s. They got some of the upgrades also seen on GP8/GP10 units, but were not rebuilt and retained original numbers. Conrail also removed dynamic braking from these units, some bean counter somewhere decided this wasn't needed on units which would mostly serve in yard and local service.