The Chrystie Street Connection and the express tracks of the Sixth Avenue Line opened on November 26, 1967, radically changing service. BB trains were combined with the former T service, which ran on the BMT West End Line in Brooklyn and the BMT Broadway Line in Manhattan. This created a through service from 168th Street to Coney Island – Stillwell Avenue via the Sixth Avenue Line express tracks and the Manhattan Bridge. This service was initially to have been signed BT but was simply signed B instead. However, during late night hours and Sundays B service did not operate, and TT shuttles continued to operate on the West End Line. Starting on July 1, 1968, the B was rerouted to terminate at 57th Street in Midtown Manhattan during non-rush hour daytime hours, extending to 168th Street only during rush hours; also, the West End Line shuttles were now run under the B designation.
1986–1988 bullets for Broadway Line service; the diamond was for rush-hour service
The reconstruction of the Manhattan Bridge between 1986 and 2004 affected B service as the Bridge's north side tracks, leading to the Sixth Avenue Line, were closed multiple times. These closures severed the connection between the northern and southern portions of the route. On April 13, 1986, the B was split into two different services. The northern B service ran via Sixth Avenue, using an orange bullet, between 34th Street-Herald Square and 168th Street, rush hours only. The southern B service ran via the Bridge and BMT Broadway Line, using a yellow bullet. It ran from Coney Island - Stillwell Avenue and terminated at Astoria - Ditmars Boulevard rush hours, Queensboro Plaza middays, 57th Street - Seventh Avenue evenings and weekends and 36th Street late nights as a shuttle. The closure of the Bridge's north side tracks essentially caused the return of pre-1967 service patterns, before the opening of the Chrystie Street Connection: The orange B more-or-less duplicated the former BB service, and the yellow B imitated the old T service.
Through B service on the Sixth Avenue Line resumed December 11, 1988, when the Manhattan Bridge's north side tracks reopened. B trains now also terminated at 168th Street on middays and evenings to partially replace the discontinued K service. During late nights, the B continued to operate as the West End Shuttle, running from 36th Street to Coney Island. B service operated to 57th Street during weekends. N service was increased to replace B service to Ditmars Boulevard.
On October 29, 1989, the IND 63rd Street Line opened; B service was extended along the new line from 57th Street to 21st Street – Queensbridge on weekends. Starting on September 30, 1990, evening service was rerouted from 168th Street to Queensbridge to replace Q service; evening A service started running local between 145th and 168th Streets to replace the B. Also on this date, because of N trains running via the Manhattan Bridge, B trains began skipping DeKalb Avenue.
On July 22, 2001, the Manhattan Bridge's north side tracks closed and B service over the Manhattan Bridge was split into two services once again, similar to the 1986 changes. However, this time the southern half of the route, running on the Broadway Line, was named the W. B service ran weekdays only, from 34th Street to Bedford Park Boulevard during rush hours and from 34th Street to 145th Street during middays and evenings.
On February 22, 2004, the Manhattan Bridge was fully reopened to subway service. B trains were once again extended through Grand Street station and over the north tracks of the Manhattan Bridge into Brooklyn. Now service operated weekdays only, between Brighton Beach and Bedford Park Boulevard during rush hours and between Brighton Beach and 145th Street on middays and evenings. The B now served the BMT Brighton Line in Brooklyn as the express (replacing the <Q> there), instead of the West End Line, which it had served in some form since 1967 to combine two weekday-only services.
From September 14, 2009 to October 3, 2011, B trains ran local in Brooklyn due to station renovations on the Brighton Line.