What do letter and numbers mean

[spjoe]

What does the letters and mumbers mean on the locomotive classification mean?

If I see a f-9 or a GP-35 and a SD40-2. What does the letters stand for and what do the numbers stand for? And what is the difference between a SD-40
and a SD-40-2?

[SSW9389]

F means freight. In the case of the F9 it is a cab unit built between 1954 and 1957. The number of an F unit is its EMD model number.

GP means General Purpose. A GP35 is a road switcher or hood unit built between 1963 and 1965. The GPs or Geeps were four axle units. The "35" is the EMD series number. There were also SD35s, SDP35s, DD35s, and DDA35s.

SD means Special Duty. An SD40 is a road switcher or hood unit built between 1966 and 1972. The SDs were six axle units. The "40" is the EMD series number and there were quite a few different models in the 40 series.

The SD40-2 took the place of the SD40 in the EMD catalog in 1972. Most of the differences between these two models was internal. The SD40-2 had improved modular electrical circuits.

[ndbprr]

You need to buy a diesel spotters guide from Kalmbach that will explain everything to you. With EMD generally the higher the number the newer the engine is also. The same thing is pretty much true for GE but the book will allow you to split hairs with the best of the nitpickers out there.

[chad thomas]

Here are the EMD domestic designations

A=Cab equipt. unit or it could mean special order(longer frame, usually for bigger fuel tank)
AC=alternator rectifier on older (2nd gen) units or on newer units AC traction motors
B=Cabless unit (may have a de-commisioned cab)
D=duty as in SD special duty or DD double duty
E=on earlier streamliners-eighteen hundred HP (6axle A-1-A)
E=at the end-EMD rebuild
e=Tier 2 emmisions compliant
F=on earlier streamliners-fourteen hundred HP (4axle)
F=on later units-full body (cowl unit)
GP=general purpose (4axle)
H=head end power equipt
I=isolated "whisper cab"
L=lightweight (may have 6axle A-1-A trucks)
M=north american safty cab or wide cab (without an AC after it implies DC
M=Morrison Knudsen rebuilt unit
MP=multi purpose (4axle switchers)
N=nine hundred HP on earlier switchers
P=passenger unit
R=rebuild
S=six hundred HP on earlier switchers
T=twelve hundred HP on earlier switchers units
T=tunnel motors on SD40s & SD45s
u=rebuilt units in canada
V=VMV re built unit
W=wide cabs in Canada (not sure on this one)
X=experimental unit
-2=modular electrical cabinet
-3=advanced electronics / traction controll

[CSSHEGEWISCH]

Check out this link for the letter and number designations on EMD's export designs:
http://emdexport.railfan.net/frame_layout.html

Designations for export designs are a bit more consistent than for domestic designs and there's some interesting power beyond our borders.