BP9 bogies but were renumbered quickly to a new 86/1 subclass; 86101–86103. These locomotives were capable of running. The most obvious visual difference between the classes is that the Class 86 has a windscreen with three windows, whereas the Class 87 only has two; likewise, the Class 86 was fitted with headcode boxes (later plated over) while the Class 87 was built without them. By the late-1970s, there was a need for more locomotives capable of operating at 100 mph. To achieve this, nineteen 86/0s were modified by the use of SAB resilient wheels, a new design of wheel in two sections separated by a rubber bearing, which allowed their top speed to be raised. The converted locos (86011–86029) were renumbered into the 86/3 series (86311–86329). As the SAB wheels were found to be insufficient for preventing track damage, in 1984 BR decided to refit all of their remaining 86/0 and 86/3 locos with flexicoil suspension, and by the mid-1980s all of the modified 86/0s and 86/3s were renumbered again as 86/4s, allowing a standardised fleet capable of 100 mph running. Further electrification of the Great Eastern Main Line in the 1980s beyond to Harwich, and saw the class employed on passenger trains from to these locations; Ipswich was energised in 1985 and Norwich in 1987. Class 86s would operate inter-city passenger services to Norwich and boat trains to Harwich until 2005, when they were replaced fully by Class 90s. In addition, many of the freightliner trains to Felixstowe were also hauled as far as Ipswich by Class 86 locomotives working in multiple. The West Anglia Main Line from Liverpool Street to was also electrified at the same time and Class 86s hauled services on this route from 1987 until 1989. A later development saw Class 86/2 and 86/4 locomotives fitted with time-division multiplexing to enable them to operate push-pull passenger trains. The main benefit of this was the requirement for fewer locomotives; for example, a second locomotive would otherwise have to join at the other end of the train after arrival at terminal stations to lead the train's onward journey. 52 Driving Van Trailers were manufactured and introduced to the WCML in 1988 to enable push-pull trains; Driving Brake Standard Opens were transferred later from Scotland to the GEML to work with their Class 86/2s. The 86/4s were already fitted with an older multiple-working system and this was gradually