The one loco in the series, that was the exception, was the E5, witch had there windows on the side, set lower, than the rest of the early E units. Here is a E5A.
The next in the evolution, was the E7's, While they still carried the square windows, in the body pannels, they now have the standard, F unit bulldog nose, loosing the long slanting nose. Also they had vertical louvers behind the cab, not seen on the earler E units. Here is a E7.
Collection of Stephen Bradley
Next up is the E8's and E9's. They are distingushed, from the E7's, by a couple of things. First, is four widley spaced portholes (round), on the side pannels. Also, they had Far-Air filter grills, along the top of the car body, that ran all the way down, insted of a few oppening, as seen on the other E units. Another is the lack of vertical louvers behind the cab. And finally, the large number board indicators, in the nose. As I said before, many of the older E units were converted and had many of the features of the E8's & 9's, so it can be diffcult to tell the diffrence. The E8 and E9, were told apart, by one thing, and this can and was also modified, along the way. It was the fact that the E8's had a rubber gasket, that held the headlight glass, slightly recessed from the casting, and the E9's had steel gaskets, that held the glass flush with the rim. Here is a E9.
Next in the line of SD's wrere the SD7's and SD9's, and SD18's. These were the first standard with carbody on a 6 axle truck, and most all SD, are just lengthened versons of the GP's, they were built along side of . The only spotting diffrence between them, is that the SD7, had its class lights inset from the side of the loco, where the SD9's and 18's, were at the edge. Look at the end of the long hoods to see this. All had a bulging radiator assembly, at the end of the long hood, as where the GP's, were flush with the side. Here is a SD9.
Collection of Joe Hughes
Next in line, was the SD35 & SDP35. These introduce the common carbody we are all used to. The diffrence between the SD35, and SDP35, is, that the P35, had a longer long hood, to have the steam generator for passenger service, added. Here is a SD35, and SDP35.
The next units in the SD line of 6 axles, was the SD45. These were EMD's first attempt, at a 20 cylinder prime mover. But with the increased fuel cost, and some other problems, the railroads quickly got rid of them, and most have been rebuilt, into SD40-2's. While all of that is internal, most all of them still have retained there distinctive SD45 looks. The way to distinguish a SD45, is by the winged radiators, at the end of the long hood, on top. Here is a SD45 body. (Now a SD40-2)
Next in the line of 6 axles, was none other than a 8 axle unit. It is the DD35. This model was built both as a B unit (witch it was origonaly only intended for), and a cab equiped verson, for only the UP. The DD35A cab equiped verson, had the modification, of having the winged radiator's, in the middle, as EMD was working on the SD45 at the time and incorporated, it into the DD35A. It was designed to be used as a B unit, between two GP35's, and was only built for the SP and UP. Here is a DD35A, and DD35, on the same train.
Up next in the continuing line, of SD units, are the SD40/SDP40's. These came about because of the problems with the SD45. Once again you can tell them the same way you wold tell a GP40, only with 6 axle trucks. The SD40 was also available with a optional steam generator for passenger service. Also there was a verson made for the IC, that wanted a larger fuel tank, for making round trips between Chicago and New Orleans, called the SD40A. It was produced on a SDP40 frame (witch is longer, to acommadate the generator), and had a larger fuel tank. The only way to tell the diffrence, is you have to notice that the fuel tank looks larger, or know the CN/IC number series for them. Here is a SD40, and SD40A.
Next is a series of units requested by the Santa Fe, that were introduced into the cataloug, and were perchased by other railroads also. They are the FP45 series. These inclued the FP45, F45, and SDP40F. While there were gaps in production of each of these, I will group them together, as they all pretty much look the same, and are the only cowl carbodie units, around with the exception of some Canadian units to come later. First was the FP45. Then came the F45, and it can be distungished, from the FP45, buy the fact that it lacks the extra length on the long hood, behind the radiator grills. Then came the world famous SDP40F for Amtrak. Its spotting diffrences, when buit, were the fact that other than the first forty produced, the nose had a flat spot in the middle, and all lacked the front nose platform, and assoicated steps, and handrails, that the FP45, and F45 had. Here are all thee, the FP45, F45, and SDP40F.
Collection of Joe Hughes
Collection of Tim Huemmer
Collection of Tim Darnell
The next major step in the the SD evoluation, is the SD38. You can tell it also apart, because it looks like a longer GP38, with 6 axle trucks. Here is a SD38.
Continuing on the next unit from EMD, was another 8 axle, the DDA40X. There is no other like it, you cant miss it. Here is a DDA40X.
Next is the SD40-2. I am keeping this seperate, because there is one spotting feature, that sets the SD40-2, apart from the SD40 (excluding the stuff that is assoicated with the -2, that I explained, back in the GP series), And that is the porches on the end of the locomotives. This is a result from the frame, being 3 feet longer, than on the SD40. CP also ordered a vairation of the 40-2, with a full width body, the SD40-2F. Here is the standard of the world, the SD40-2, and SD40-2F.
Next is the result of taking the SD45, and putting the -2 electronics inside of it. Now you have the SD45-2, and it to also had a 20 cylinder prime mover. This locomotive, has to be the biggest change from a non -2 to a -2. The reasoning for this is that about this time, EMD was looking for and found a way to increase cooling capicity (by adding 4 more feet to the length), and put it to use on the SD45-2 model. Spotting features of this unit, are the fact that we have now returnd to the radiator grills, on the side of the hood, not flaired out, like the 45. Also with the extra 4 feet, there is no porch on the rear of the unit. Also the three, radiator fans on the top are spaced out farther apart. Here is a SD45-2.
The next variation of the SD40/SD45/-2's, was only buit for the SP companies, and the DRGW, and it is the SD40T-2, and SD45T-2. The same as the SD40 & SD45, the 40's have a 16 cylinder prime mover, and the 45, has a 20 cylinder verson. The only diffrence, in the T verson (Tunnel motor) is the rear radiator section. It has the intake grills, down on the walkway of the locomotive, and has the radiators, on the top of the long hood, giving the intake's the empty look, (you can see through them). The only diffrence that you can tell between a SD40T-2, and the SD45T-2, is by the radiator fan acess doors, and the long hood, above the radiator intake. The 40 verson, has only two, and the 45 has three. Here is a SD40T-2, followed by a SD45T-2.
Collection of Patrick
Up next is the SD50 and SD60. Because of the minor diffrences, between these two units, I am going to put them all together, in one posting. The SD50/60's, can be told apart, from the rest, by a couple of things. First as on the GP50, the rear radiator section, has gotten much wider. Second unlike most of the GP50's produced, the SD50, has the angled traction motor blower duct, behind the conductors side of the cab (I had also touched on this in the GP's). The only diffrence between the SD50, and SD60 is the fact that the 50's, have 6 latched doors under the radiator grills, on the side of the long hood, vs. 8 on the 60's. Also built only for the CN, is the SD50F. This is a full cowl carbody type unit (like the F's and E's). They are the only ones around, and also includ four SD60F's. The SD60F's, have no diffrence in the body, and are only distingushed by the fact that they have a 710 prime mover inside. And like I said before, only the CN has the 50F's and 60F's (4). Finnally at the end of SD60 production, came the next biggest change, in U.S. locomotive history, the wide cab. Only the SD60's have this feature, no 50's were built this way. And also there is a three window verson, and two window, verson, with the two window becomming standard. Here are in this order, a SD50, SD50F, SD60, and SD60M.
Collection of Paul Amos
Collection of Gregg Pullano
Collection of Railroadfan.com
Next in the chain, is the SD70/M/AC. SD70's were built both with standard cabs (most undoboutly the last of its kind) and with wide cabs. They also produced the SD70AC. To start off with, the closest to the SD60's in looks, is the SD70AC's. They look like a SD60, but to tell the diffrence apart, they have extra louvers, at the end of the long hood, under the radiator section. They also can can be distingushed by the fact that on the engineers side of the long hood, is the breakwheel. With that being said, CSX ordered 130 SD70AC's, in 2003, that looked nothing like the origonals. These can be spotted by a couple of things, they are only in YN3 paint, they have flaired radiators (I think we have see that befoe), and on the enginers side of the long hood, it has a bulge, that is explained later under the SD75's. The SD70's both standart cab, and wide cab, have the biggest changes. The best way to tell the diffrence, between the 60's and 70's, is the traction motor blower housing's. On the SD70's, it is no so much a bulge, as it is now a box. You can still see it in the same place, behind the conductors side of the cab on the long hood, but now it looks like a rectulanger box. Also on the standard cab, you can see a bulge, in front of the engineers window, on the side of the short hood. Later on in SD70M production, EMD was looking for a way to meet the new tougher EPA standars being intoduced. The result of that was that the SD70M's grew wings on the rear radiator section at the top of the long hood. There are only two railroas, that have these locos, they are the UP, and NS. There were also SD75's produced, but only in wide body verson. These can be told apart, by the fact that there, is another traction motor blower housing type of bulge, on the engineers side, behind the cab. Also introduced, on the 70's, was a new truck underneith, the HTCR. Here is a SD70AC origonal, then a SD70AC "new" verson (CSX only), a SD70, SD70M standard, followd by SD70M flaired radiators, and SD75.
Collection of Ed Hopson
Collection of Ed Hopson
Next on the list, is the SD80AC, SD9043AC, and SD90AC. All are in the same body, with minor variations, between them. These locomotives, look like nothing else ever before seen, as they have a huge bulge, behind the conductor side of the cab on the long hood, and have the verry large, verry flaired radiators. First the SD80AC, only built for the Conrail, (and now owned by CSX, and NS), is told apart, frorm the SD90AC, by only one minor sign. On the end of the locomotive, rear of the long hood, neer the top, there is a notch, in the end of the hood. The SD90's do not have that notch, the end of the body is flat. The only diffrence, externaly between the SD90, and the SD9043, is the fact that the SD9043, has the tops of the middle of the long hood (where the prime mover is, ie. engine compartment), is square, with the roof. The SD90, has a angle to the top of the hood, between the sides, and top. The reason for the SD9043, was the fact that EMD was having problems, with the 20 cylinder 6000 HP. prime mover (where have we heard that before), and the railroads wanted fast delivery, of the locomotives, that EMD, put a 4300 HP. engine, in the locos, with the prommise that when the 20 cylinder had the buggs worked out they would pull the 4300 HP motor out and put in the 20 cylinder 6000 HP power plant in. Here is a SD80AC, then SD90 rear view, so you can see the diffrence, followed by SD9043AC, and a SD90AC.
Collection of Tim Huemmer
Collection of Rick C.
This is the last of the "big sixes", for the time being, the SD70ACe/SD70M-2. These at first glance, look like a SD80/90, but at further eximnation, they are shorter, and the raidator section, dose not flair out as far. There are no diffrences between the 70ACe, and 70M-2. So far there is only two takers of the 70M-2, NS and CN. Here is a SD70ACe.
Next time, GE 6 axles.
