5000-series bodies had a curved profile previously used by North Shore Line and then Chicago, Aurora & Elgin cars which operated on the "L".

The floor width was the 8 ft 8 in (2.64 m) needed for platform clearance, then above the sides curved outward, so the car was wider at seat level.

[5][1] The 5000s had modified Clark and St. Louis trucks with 28 in (711 mm) wheels designed for high speeds.

These had a top speed of 50, which was adequate for CTA needs until the high-speed Skokie Swift shuttle started in 1964.

The first 200 cars were built with new components, including Clark B-2 trucks, the next 310 cars had Clark B-2s salvaged from Pullman streetcars, and the final 210, plus most of the similar 1-50 class, had St Louis B-3s salvaged from St Louis streetcars.

(The western section of the Lake line was elevated in 1962; however, it remained equipped entirely with 4000s until the arrival of the 2000-series cars from Pullman-Standard in 1964.)

When the Dan Ryan line was opened in 1969, newer cars were assigned there, but 6000s were sometimes used for special movements.