Southern Pacific experienced problems with locomotives overheating in tunnels. This brought about a major design change in the new SP SD45-2s.

The traditional EMD sidemounted radiators and roof fans were replaced with roof-mounted radiators, internal fans and a large opening at the bottom of the rear of the long hood. This allowed for cooler air to be pulled upward through the radiators.

The new locomotive was nicknamed “Tunnel Motor,” both for the problem it addressed and the opening in the long hood. While SP initially bought the SD45T-2, Rio Grande chose the 3000-horsepower SD40T-2. SP also purchased a large numbers of SD40T-2s.

Today, both SP & D&RGW are gone, absorbed by Union Pacific. But the Tunnel Motors remain, many serving on Class II roads and short lines across North America. And just like the SD40-2's these will continue to work the rails for many years to come.

The D&RGW ran “through the Rockies, not around them.” The first Rio Grande SD40T-2 order was delivered in October 1974 and included road numbers 5347 and 5355. Number 5368 arrived on the second order in July 1975.

General Model Features:

• See-through radiator intake grilles
• See-though exhaust stack
• Snowplow and/or MU catch boxes
• MU hoses
• Coupler cut bars
• Dynamic or non-dynamic brake
• Minimum radius: 18”
• Recommended radius: 22”
• DCC Ready
• 81” nose with ratchet brake and gyralight
  
• Cab-mounted headlight
  
• Cab-side vent
  
• 4000-gallon fuel tank
  
• Double fuel fills
  
• EMD-style snowplow
  
• Nathan M3 air horn
  
• Positive Train Control (PTC) box included—the PTC box is not applied since Rio Grande took delivery without this feature