An EMD TR5 'cow and calf' set await assignment at UP North Yard in Salt Lake City on June 18, 1977. The two units, connected semi permanently by a draw bar, were built by EMD for the UP in Sept. 1951. In 1952, the entire fleet of eight sets (UP 1870-1877) were equipped with dynamic braking for helper service on Cajon Pass in California, and on Cima Hill in Nevada (with the gear later removed). In 1968, the 1870-1872 were modified with 1400 gallon fuel tanks with air reservoirs relocated on top of car body for service in the North Platte hump yard. After the modifications, they had 521,600 pounds total cow/calf operating weight. By June of 1976, the UP 1872 was mated with UP 1870B upon retirement of UP 1870 and UP 1872B. By June of 1982, the pair were retired from the roster with the UP 1872 going on to be rebuilt as SW10 No. 1234 and the UP 1870B 'calf' was scrapped. A big thank you to Don Strack for the historic and technical information.
