Amtrak ordered 25 P30CHs in 1974, following up on its order of 40 EMD SDP40Fs in 1973. The P30CH was the first Amtrak diesel locomotive built from the factory to offer HEP ( head end power ) in the form of 2 Detroit Diesel generator sets, each rated at 375 kW. The six-axle P30CHs, which cost Amtrak $ 480,000 each,  :105 were plagued with mechanical problems and were never very popular with crews or Amtrak management. In the mid-1970s Amtrak moved away from six-axle designs in favor of four-axle units; four-axle locomotives could better handle routes with numerous curves.  :34 Ultimately the four-axle EMD F40PHs quickly began to supersede the P30CHs soon after their introduction by Amtrak.
Turboliners arrived on the Detroit run on April 10, 1975. Additional equipment allowed Amtrak to add a round-trip in late April; the arrival of a third trainset in May made Chicago–Detroit the "first all-turbine-powered route". After one year of operation, ridership on the corridor had increased by 72 percent. The fixed capacity of 292 passengers on an RTL trainset proved an impediment; Amtrak could not add capacity when demand outstripped supply. Amtrak replaced one of the trainsets with a conventional locomotive hauling then-new Amfleet coaches in 1976; Turboliner service ended altogether by 1981 as more Amfleet equipment became available.