RoyBoy posted:Pardon my ignorance, but what are the external differences between the GP7 and the GP9?
In 99.9% of the units, the best visual difference is the vertical hand-rail stanchions; the GP7 having solid bar-stock stanchions, vs. the "U Channel" vertical stanchions on the GP9. The GP9 will have all sorts of improvements throughout its production, from larger diameter cooling fans to larger capacity fuel tanks and relocated main air reservoirs.
In the toy train world, the absence of dynamic brake blister is called a GP7 and adding the blister is called GP9, but that can't be what scale modellers call the differences.
That apparently was an old Lionel "explanation", which of course is totally false. Both the GP7 and GP9 models could be ordered from EMD with or without dynamic brake (same as with or without a steam generator for passenger service).
