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KCS 4504 EMD SD45T-2.jpg
Type and origin
Power type Diesel-electric
Builder General Motors Electro-Motive Division (EMD)
Model SD45T-2
Build date February 1972 – June 1975
Total produced 247
AAR wheel arr. C-C
Gauge 4 ft 8 12 in (1,435 mm)
Length 70 ft 8 in (21.54 m)
Fuel capacity 4,400 US gal (16,700 l; 3,660 imp gal)
Prime mover EMD 645E3
Cylinders V20
Performance figures
Power output 3,600 hp (2,680 kW)
Nicknames "tunnel motor"
Disposition many still in service as of 2010; one donated to California State Railroad Museum

The SD45T-2 is a 6-axle diesel-electric locomotive built by EMD for the Southern Pacific Railroad. Like the similar SD40T-2 it is nicknamed a "tunnel motor". 247 were built from February 1972 to June 1975, including 84 for SP's subsidiary Cotton Belt. From April 1986 to December 1989 about half were rebuilt and designated as SD45T-2R and 24 of the 126 rebuilds were built for Cotton Belt.

The SD45T-2 is an SD45-2 with cooling system modifications. The intake for radiator cooling air was moved to the walkway level and the cooling fans themselves were under the radiator cores, instead of above. Tunnel motors were built to perform best in tunnels in mountainous areas in the western United States. The air intake grills at the lower rear of the locomotives' long hoods were intended to bring cool and clean air into the radiator section. The larger area of the intakes would also provide a less restrictive airflow.

Another tunnel motor, the SD40T-2, is similar to the SD45T-2. One spotting difference is the longer hood on the SD45T-2 to accommodate the V20 prime mover vs. the V16 used on the SD40T-2. The SD45T-2's cab is further forward on the frame, so there is less "front porch". This mimics the differences between the SD45-2 and the SD40-2. Another spotting difference is the SD45T-2's three fan access doors on each side above the cooling air intake, while the SD40T-2 has two.

EMD SD45T-2 vs SD40T-2 radiator fan motor access doors

Like the SD40T-2, some of SP's SD45T-2 tunnel motors were obtained by Kansas City Southern Railway, Bessemer and Lake Erie Railroad, Duluth, Missabe and Iron Range Railway and by the Union Pacific Railroad when it merged with SP in 1996.

Some SD45T-2s were rebuilt and designated to SD45T-3, SD40T-3 and SD40-2T, in addition, some locomotive leasing companies own the SD45 tunnel motor locomotives. They are scattered all over the United States and are an increasingly rare sight.

As of January 2003, SD45T-2R SP No. 6819 (formerly SP 9193) was donated to the California State Railroad Museum in Sacramento.