Locomotive Descriptions and Phases - EMD SD38-2, SD40-2
CBNS #3366, a Phase 3c SD40-2 originally built as BN #8151, seen in 2015. The rear-most radiator fan has been replaced with an older fan.
The SD38-2, SD40-2 and SD45-2 were introduced in 1972 as replacements for the SD38, SD40 and SD45 respectively. They retained the same respective horsepower ratings but received a host of mechanical and electrical upgrades, with the most visible difference being the longer frame with HT-C trucks. Internally, the most significant upgrade was the use of solid-state modular electronics. While the SD38-2 and SD45-2 were relatively slow sellers and ceased production in the late 1970s, thousands of SD40-2 variations were built as it became the most popular locomotive of the late 20th Century, with peak production in the late 1970s and the last variant (the full-cowl SD40-2F) built in 1988.
The SD38-2 and SD40-2 were very similar externally, with the relatively long frame and short hood resulting in large "porches" at either end. The SD38-2 had two radiator fans and two exhaust stacks, while the SD40-2 had three radiator fans and a single turbocharger exhaust stack (changed to a flat silencer housing on later units). The SD45-2 had a single exhaust stack and three radiator fans spread out over a distinctively longer hood that filled the extra frame length. "Tunnel motor" variants, the SD40T-2 and SD45T-2, rode on a still longer frame and had a redesigned radiator area with low air intakes, internal fans and roof-mounted radiator grills. Wide-nose units built for CN were otherwise similar to other SD40-2's, but the full-cowl SD40-2F built for CP was in fact closely derived from the SD50F built for CN, and its carbody and general construction had little in common with other SD40-2's.
In the first two decades of the 21st Century, the SD40-2 was gradually replaced by newer, higher-horsepower units in mainline service on large railroads, with gradual scrapping of some units beginning around 2010. Nevertheless, by the mid 2020s, well over a thousand were still in service on Class I railroads more than 50 years after the model was first introduced, many of them overhauled or rebuilt. Many more continued in service with leasing companies or smaller railroads.
Transition: From late SD38/SD40/SD45 to early Dash-2 series
On all six-axle Dash-2 units, the frame was lengthened by just over 3' to accommodate the longer HT-C trucks while keeping enough room for the standard 4000-gallon fuel tank. Depending on the thickness of the pilot end plates (0.75" or 1.5") the overall length was either 68' 8.5" or 68' 10", compared to 65' 8" or 65' 9.5" for the SD38/SD40/SD45. The SD40T-2 and SD45T-2 were built to an overall length of 70' 8" with 1.5" end plates.
The HT-C truck looked superficially similar to the earlier Flexicoil, but it was a substantially different design, with an all-new frame casting, taller primary springs, stiff rubber pads for the secondary suspension (in place of large coil springs), unequal axle spacing (79.625" for the outer axles and 83.75" for the inner axles), and all traction motors facing the same direction (the reason for the added length). The bolster centers were offset outward by 1.25" from the center axle on each truck and were 2.75" closer to the end plates than on earlier units; excluding tunnel motors, this made for bolster centers of 43' 6" and a distance between the center axles of 43' 3.5".
Conrail units were built with Flexicoil trucks but retained the same frame, leaving a large gap between the trucks and fuel tank. Railroad diagrams list the bolster centers on Flexicoil-equipped units as 43' 6", but as the Flexicoil trucks had even axle spacing with the bolster lined up with the middle axle, such a dimension would put the trucks too far toward the ends and cause clearance issues with the steps and draft gear. I haven't confirmed the dimensions definitively, but photo measurements suggest that the Flexicoil trucks were located the same distance from the end plates as on the earlier SD40, which would give truck centers of 43' 0.5".
On all six-axle Dash-2 units, the front section of the hood (housing the inertial air intakes and blower duct) was lengthened by roughly 8". On the SD38-2 and SD40-2, this added length was not enough to compensate for the increased frame length, and the result was significantly larger platforms at either end - with the rearmost wheel entirely out from under the end of the hood. On the SD45-2, however, the rear of the hood was also lengthened to fill up the extra frame length, and the added space was used to house longer, narrower radiators that did not require the canted intakes used on the SD45. The longer radiators resulted in three very widely spaced rooftop radiator fans.
At the start of EMD Dash-2 production, almost every part of the cab and hood was changed in some way. Compared to previous SD units, the following changes were made to the SD38-2 and SD40-2:
Cab and cab sub-base
- Battery box covers bolted rather than hinged
- Left-side battery box cover lengthened rearward
- Right-side battery box cover lengthened forward
- Left front handrail stanchion moved rearward
- Right front handrail stanchion moved forward
- Riveted, rectangular cab side panel around side windows
- Rear cab roof overhang
- Larger electrical cabinet air filter box
- Larger handbrake notch in nose
Hood
- Modified central air intake and blower duct
- Longer front hood section (creating a larger gap between the blower duct and cab)
- Oblong water-level sight glass on the right rear side of the hood
- Rear hood doors grouped 2-2-2-1 instead of 1-2-4
- Circular access hatches added at the top corners of the long hood end
Underframe and walkway
- HT-C trucks
- Frame lengthened by 3', resulting in:
- One additional handrail stanchion per side
- Revised underframe pipe and cable routing
- Longer walkway blower duct
- Optional metal ballast plate above fuel tank eliminated; fuel tank approx. 2" closer to underframe
Phases
When making phase descriptions, I always face the dilemma of how to combine various existing phase descriptions with additional details from my own observations - resulting in my phase descriptions evolving over the years.
- In the early 2000s, I adopted a simplified version of the descriptions by Scott Chatfield, which I obtained indirectly from an article about UP SD40-2's by John Bruce (no longer online).
- In 2010, I expanded some of the details but kept most of the phase numbers the same.
- In November 2014, I further expanded the phases based on the GP40-2 roster compiled by Robert Sarberenyi (as well as adding additional background information). These phases were very similar to Chatfield's SD40-2 phases.
- In April 2016, I received an outstanding SD40-2 roster from Brian Bennett and attempted to incorporate the additional details as subphases of my existing phase numbers. In the following years I made a number of additions but no changes to the phase numbers.
- In March 2025, after discovering further detail changes in GMD production, I decided to adopt Bennett's phases mostly as-is. I finally abandoned the original sequence of Phase 2b through Phase 3 as I could find no way of reasonably accounting for 8 phase variations within what was originally Phase 2a.
The only significant change I made was with phases 3b and 3c. Bennett's original Phase 3c denoted the standardization of the bumped fuel cutoff switch and rearward right side sill notch (present on many units from Phase 1a2 onward), but I was reluctant to include a separate phase distinction when it was just an existing feature becoming standardized. However, I did find a more significant change that occurred around the same time when the front traction motor cables were combined and rerouted under the left side of the cab, leaving a notably cleaner underframe on both sides ahead of the fuel tank; I've labelled this as Phase 3c1.
Summary of phases:
| Chatfield | 1 | 1b | 2 | 2b1 | 2b2 | 2c1 | 2c2 | 2d | 3 | ||||||||||||||||
| Mine (2010) | 1a | 1b | 2a1 | 2a2 | 2b | 2c | 3 | ||||||||||||||||||
| Sarberenyi (GP40-2) | 1a1 | 1a2 | 1b | 2a1 | 2a2 | 2b1, 2b2 | 2b3 | 2c1 | 2c2 | 2d | 3a, 3b, 3c | ||||||||||||||
| Mine (2014) | 1a1 | 1a2 | 1b | 2a1 | 2a2 | 2b1 | 2b2 | 2c1 | 2c2 | 2d | 3 | ||||||||||||||
| Mine (2016) | 1a1 | 1a2 | 1b1 | 1b2 | 1c1 | 1c2 | 2a1 | 2a2 | 2a3 | 2a4 | 2b1 | 2b2 | 2c1 | 2c2 | 2d1 | 2d2 | 3 | ||||||||
| Bennett (2016) | 1a1 | 1a2 | 1a3 | 1b1 | 1b2 | 1c1 | 1c2 | 1d | 2a1 | 2a2 | 2a3 | 2b | 2c1 | 2c2 | 2c3 | 2c4 | 2d1 | 2d2 | 3a | 3b1 | 3b2, 3c | 3d1 | 3d2 | 4 | |
| Mine (2025) | 1a1 | 1a2 | 1a3 | 1b1 | 1b2 | 1c1 | 1c2 | 1d | 2a1 | 2a2 | 2a3 | 2b | 2c1 | 2c2 | 2c3 | 2c4 | 2d1 | 2d2 | 3a | 3b | 3c1 | 3c2 | 3d1 | 3d2 | 4 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
In theory, most of the changes made to the SD40-2 would also apply to other members of the EMD 6-axle Dash-2 series. These phases could reasonably be used for the SD38-2 and SD40T-2, although those two models didn't span all phases and a few details would not be relevant (such as the exhaust silencer for the SD38-2, or the radiators and fans for the SD40T-2). The SD45-2 and SD45T-2 ended production in 1974 and 1975 respectively - and since their limited production never made it past Phase 1b1, I haven't bothered listing phases for them.
These phases do not apply to Canadian (GMD) SD40-2 and SD40-2(W) production, which followed a different (though similar) sequence of detail changes (see GMD SD40-2 Phases). However, a few EMD SD40-2 orders (BN 7167-7205, 7206-7235 and 8074-8089) were built by GMD in Canada when EMD was at capacity. Unlike other GMD SD40-2's, they were built to BN specifications and were virtually identical to their US-built counterparts, except for having a smooth (rather than ribbed) blower duct and HT-C trucks cast by Dofasco instead of Rockwell.
Numbers correspond to the illustrations shown below.
| Phase | 1a1 | 1a2 | 1a3 | 1b1 | 1b2 | 1c1 | 1c2 | 1d | 2a1 | 2a2 | 2a3 | 2b | 2c1 | 2c2 | 2c3 | 2c4 | 2d1 | 2d2 | 3a | 3b | 3c1 | 3c2 | 3d1 | 3d2 | 4 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dates | 72-01 - 72-12 | 72-11 - 74-05 | 74-05 - 75-03 | 75-01 - 75-07 | 75-08 - 75-12 | 76-02 - 76-03 | 76-07 - 76-09 | 76-11 | 76-11 - 76-12 | 77-01 - 77-02 | 77-02 - 77-05 | 77-05 - 78-01 | 78-01 - 78-06 | 78-03 - 78-08 | 78-08 - 79-01 | 79-01 - 79-03 | 79-03 - 79-07 | 79-07 - 79-12 | 79-12 - 80-02 | 80-01 - 80-03 | 80-01 - 80-09 | 80-09 - 81-03 | 81-08 - 81-10 | 81-10 - 81-12 | 83-04 - 86-02 |
| Inertial air intakes 1 | Ridge added along top | Ridge added along bottom | |||||||||||||||||||||||
| Frame side sill | 8" at ends, 5" in middle | Right side rear sill notch moved rearward when bumped fuel cut-off housing present | 5" over entire length | ||||||||||||||||||||||
| Hand brake 2 | Ratchet; angled chain housing | Vertical chain housing | Wheel (some units retained ratchet) | ||||||||||||||||||||||
| Pilots 3 | Straight upper end plate corners, straight coupler cut levers | Notched upper end plate corners, raised coupler cut levers | Narrower anticlimbers | ||||||||||||||||||||||
| Battery box covers 4 | Bolted, 2 small (Latched, lift-off tabs on BN units) | Larger louvres | Horizontal rib added (bolted version only) | Latched, lift-off tabs, 2 x 2 louvres (except SOO 6617) | |||||||||||||||||||||
| Phase | 1a1 | 1a2 | 1a3 | 1b1 | 1b2 | 1c1 | 1c2 | 1d | 2a1 | 2a2 | 2a3 | 2b | 2c1 | 2c2 | 2c3 | 2c4 | 2d1 | 2d2 | 3a | 3b | 3c1 | 3c2 | 3d1 | 3d2 | 4 |
| Radiators, fans 5 | Square wire grid intakes; curved grabiron behind fans; flat-top radiator fans | Corrugated intakes; relocated lift ring and flag holder aft of intakes | Angled grabiron behind fans | Q-type radiator fans | |||||||||||||||||||||
| Cab side 6 | Riveted side panel with 11 rivets along top/bottom | Riveted side panel with 13 rivets along top/bottom | Welded side panel | ||||||||||||||||||||||
ECAFBElectrical cabinet air filter box, located on the left behind the cab 7
| Separated from cab | Flush with cab | |||||||||||||||||||||||
| End handrails 8 | Flush with pilots, inward-facing central handrail stanchion supports | Wrap around pilots slightly, outward-facing central handrail stanchion supports | |||||||||||||||||||||||
| Cab sub-base panels 9 | Hinged | Lift-off tabs | |||||||||||||||||||||||
| Short hood 10 | Standard: 81"; Snoot: 116" with 81" slope and 35" flat section near cab | Standard: 88"; Snoot: 116" with constant slope; Circular vent on right side | Snoot: 116" or 123"; Circular vent moved upward | Bolted hatch added on top | |||||||||||||||||||||
| Phase | 1a1 | 1a2 | 1a3 | 1b1 | 1b2 | 1c1 | 1c2 | 1d | 2a1 | 2a2 | 2a3 | 2b | 2c1 | 2c2 | 2c3 | 2c4 | 2d1 | 2d2 | 3a | 3b | 3c1 | 3c2 | 3d1 | 3d2 | 4 |
| Stepwells 11 | Shallow angled plate, wide top steps | Deeper angled plate, narrower steps | |||||||||||||||||||||||
| Fuel tank vent pipe 12 | Approx. 2.25" outer diameter, extended up into blower duct housing | Approx. 2.75" outer diameter, junction box below walkway | |||||||||||||||||||||||
| Trucks, underframe 13 | Revised center axle shock strut (inconsistent until Phase 2c1) | Revised air reservoir piping on left side | |||||||||||||||||||||||
| Jacking pads 14 | Tall (no casting holes after approx. Phase 1b1) | Short | |||||||||||||||||||||||
| Dynamic brakes 15 | Batten strip at rear of dynamic brake housing | No batten strip | Dynamic brake housing moved rearward, lift rings moved closer to fans | ||||||||||||||||||||||
| Exhaust 16 | Raised exhaust stack | Silencer with opening at rear | Silencer with opening at front | ||||||||||||||||||||||
| Traction motor cables 17 | #1 motor cables on left side, #2 cables on right side; both routed along underframe to near fuel tank | #2 cables on left side, #1 and #2 cables routed under cab; slightly revised #1 cable routing (1980-08) | |||||||||||||||||||||||
| Blower duct 18 | Flat, wide, two ribs | Angled "laundry chute" | |||||||||||||||||||||||
| Phase | 1a1 | 1a2 | 1a3 | 1b1 | 1b2 | 1c1 | 1c2 | 1d | 2a1 | 2a2 | 2a3 | 2b | 2c1 | 2c2 | 2c3 | 2c4 | 2d1 | 2d2 | 3a | 3b | 3c1 | 3c2 | 3d1 | 3d2 | 4 |
Other details
- Some units prior to Phase 4 (notably BN units) were built with battery box covers with latches and lift-of tabs.
- Various as-built pilot options: standard footboards (up to 1975), plow (various sizes), rock deflector (2 types), flat end plate
- There were two variations in step spacing, depending on railroad.
- An oblong cab vent appears on most units starting with Phase 2a (generally on the left side of the cab at the rear) along with a circular vent on the right side of the short hood.
Illustrations
These drawings illustrate typical Phase 1a1, Phase 3a and Phase 4 SD40-2's built to NdeM specifications. Aside from the additional junction box above the MU connector on the Phase 1a1 unit and the clasp-brake trucks on the Phase 3a and 4 units, they are very generic SD40-2 variations.
Phase 1a1 - Phase 3a - Phase 4
References
Bennett, B. (2016). Master SD40-2 Production History. (Spreadsheet).
Biel, Charles. (2013). EMD SD40-2. Retrieved November 2014 from http://archive.trainpix.com/BN/EMDORIG/SD40-2/INDEX.HTM
Bruce, J. (2000). Union Pacific SD40-2s. Retrieved from http://www.german-railways.com/USA/UP/Locos/SD40-2.htm
CNRPhotos. (2006). Data Sheets - Motive Power. Retrieved January 2010 from http://www.cnrphotos.com/gallery2/main.php?g2_itemId=18406
Foster, Gerald. (1996). A Field Guide to Trains. New York, NY: Houghton Mifflin.
Sarberenyi, R. EMD's GP40-2 - Original Owners. Retrieved November 2014 from http://www.trainweb.org/jaydeet/gp40-2.htm
Southern Railway. (1980). Diesel Electric Locomotive Diagrams - 1980. Retrieved November 2014 from http://southernmodeler.info/SRdiagrams.htm
Unofficial EMD Homepage. (2005). SD40-2 Order Numbers. Retrieved November 2014 from http://www.trainweb.org/emdloco/sd40-2.htm