Union Pacific’s DDA40X
The DDA40X locomotive was built solely for the Union Pacific railroad. Only 47 were build (6900-6946), and only 13 of them still survive today and one of those actually still operates. The DDA40X would be the most powerful locomotive built with a total of 6,600hp. The first one to arrive on UP property was the 6900 in 1969, delivered in time to celebrate the 100th anniversary of the Golden Spike at Promontory Point in Utah.
The DDA40X went by two nicknames, Centennial and Big Jack. In 1980, the economic slowdown cause a slow down in freight traffic, so the entire fleet was retired. In early1984 traffic patterns picked up and UP needed locomotives, so 25 of the Centennials were deemed ready to go back to work. In December that year, the 25 Centennials were once again retired. It was more efficient and cost effective to use 2 or 3 SD60s to power a train.
The Centennials were long, just over 98 feet, and weighed in at 270 tons. They ran on a pair of rigid, 4-axle trucks, making it a D-D wheel arrangement. This long rigid truck made it difficult to negotiate sharp curves. The “X” designated it had experimental components like a new traction motor, a Dash 2 electrical cabinet, and other new features. This meant that spare parts were not common with other EMD products, so if a DDA40X needed repairs in Portland, it would take a few days to get parts.
Seeing a DDA40X in the Northwest was a real treat. They did visit Albina yard in Portland, but the sharp curves at Argo kept them from going to Seattle; it might have happened once, but that’s about it. Today if you want to see a DDA40X in operation you have to wait until Union Pacific operates the 6936 on special occasions.