The AM4 or Class 304 fleet were introduced for the electrification of the West Coast Main Line in the 1960s, the first section to open was that between Crewe and Manchester in September 1960, followed in January 1962 by the Crewe-Liverpool section and in various stages south to reach London Euston by November 1965. The AM4 were dedicated to the suburban services and after electrification through to Euston were not usually used much south of Rugby, leaving this operation to the AM10s.
The first 15 sets for the Crewe-Manchester route had extra accommodation in the MBS with eight 3+2 bays, whereas sets built after No. 015 had seven 3+2 bays.
When first delivered, the first eight of the second batch were used on the Eastern Region's Shenfield-Southend route to cover for stock shortages, but these soon joined the rest of the fleet for LM use.
The sets remained the mainstay of suburban and outer suburban passengers operations over the northern sections of the LM until the 1980s when rationalisation saw sets shortened to 3-car formations for Manchester area use.
The sets remained in traffic until the mid-1990s when they were replaced by Class 323 electric stock.