A piece of advice to you and other newbies - Spend some of your time reading some background material on what your interested in. Check out of parts of the train.com website. There is a wealth of information available right here (and not in the forums or from its members) if you would just spend some time looking around. Indices, glossary of terms etc.
“Geep: The affectionate term describing EMD’s popular GP (General Purpose) series, which initially was meant for the first generation units, the GP7, GP9, and GP18 but later went on to describe all of EMD’s GP models.”
Ya “G.P.” means General Purpose, “S.D.” means Special Duty. FWIW I will refer to them as Geeps but not when used with the number…that is I sometimes hear someone refer to a GP-9 as a “Geep Nine”. I prefer to say “G.P. Nine” in that context.
Of course Geeps and F’s would accelerate faster than an E Unit, The Geeps and F’s have 40" diameter Wheels versus the 36" Diameter Wheels of the E Unit. So for every revolution of the axle the Geeps and F’s would go 4" further. They also had better tractive effort as they did not have an idler axle on each truck. Which is why F’s were used in the mountains by the GN, NP, B&O and others.
Not sure… but it may be some kind of diseasally thingy from some time in the future. Of course I seem to be stuck in the year 1925 on the Seneca Lake, Ontario, & Western RR…[:-^]