• EMD "Tunnel Motor" official thread (covers all variations)

  • Discussion of Electro-Motive locomotive products and technology, past and present. Official web site can be found here: http://www.emdiesels.com/.
Discussion of Electro-Motive locomotive products and technology, past and present. Official web site can be found here: http://www.emdiesels.com/.

Moderator: GOLDEN-ARM

  by amoreho1
whats the difference between an sd40 and sd40t ?

  by Phil Hom
The T version as on the SD series were used only on the Dash-2 version. The locomotives were designed with a cooling system that drew cooler air that is closer to the track level. In tunnels and in snow sheds, the locomotive without the modified cooling system would overheat since it is drawing air close to the roof of the tunnel, which is hot for units other than the lead units. Many export models used this type of cooling until the SP requested the modification for domestic use.

Later EMD would use the T meaning turbo charged engin on the GP15 and on the MP15.

  by Steve F45
besides what has already been mentioned the car bodies are different, well longer then the regular sd40-2. You can can see the difference between the two.

  by amoreho1
i thought there was some other difference

  by trainiac
Only the SD40-2 and SD45-2 were produced in "tunnel motor" variations, the SD40T-2 and SD45T-2.

SD40-2 and SD45-2 are both 68' 10" over the coupler pulling faces.
SD40T-2 and SD45T-2 are 70' 8".

SD40-2 and SD45-2 have radiator fans on the roof that suck air through flush radiator grills at the top of the hood.
SD40T-2 and SD45T-2 have internal radiator fans that bring air in through a much larger intake that's at the level of the walkway, and blow it through radiators mounted on the roof.

The extra frame length is to accomodate the redesigned radiator section; from the engine compartment to the front, they are the same as an SD40-2 or SD45-2.

The SD40T-2 and SD45T-2 were only ordered by the SP/SSW and DRGW, so they have some unique details typically specified by those roads (lights, jacking pads, plows etc). The "T" designation is for "Tunnel"--the different cooling system eliminated cooling problems in tunnels experienced with regular EMDs. The idea is that the tunnel motors draw in the cooler air lower down in the tunnel, since the air at the top of the tunnel is very hot from the exhaust.
  by Steve F45
Besides the prime mover, are there any other differences in the two? Frame length, cab, radiator?

  by timz
Frame length is the same, but hood length is longer on the 45T-2.

  by Steve F45
ok thanks for that link. i had forgotten about that discussion. So it could be easy to get confused looking at them if you didn't know the hood was longer.

Also rear platforms have cool ladders, instead of stairwells.

  by NHRDC121
Number of access doors, per side, for the radiator cooling fans. SD40-T2's have 2, SD45-T2's have 3. These are visible directly above the large air intakes at the rear of the long hood.

  by Steve F45
but from a modeling standpoint you wouldn't be abel to tell unless you were looking at it real close?
  by dash7
hi there,does anyone know how up has replaced former sp sd40t-2's(road no's#8230 - 8341 #8350 - 8391 #8489 - 8573) and 45t-2's on the tehachapi route and how they have overcome over heating without resorting to lower air intakes?

  by byte
Someone wrote in this same question several years back to Trains magazine's Q&A section. I believe the answer was "in short, by running faster trains." Seems that they've upgraded the track to a point where these diesels are spending less time in the tunnels, and therefore there's less of an opportunity for them to overheat.