GM B platform

The B platform, or B-body, was General Motors' full-size rear-wheel drive automobile platform. It was closely related to the C-body and D-body and was used for convertibles, hardtops, coupés, sedans, and station wagons.

The B-body was used for the Pontiac Streamliner Torpedo and Streamliner, the Oldsmobile Series L, Series 70 and Series 88, the Buick Special and Century, the LaSalle Series 50 and the Cadillac Series 60, Series 61 and Series 63. The B-body became GM's base model platform in 1958, when all existing Chevrolet products were upgraded to the B-body.

For the 1959 model year, the previous A and B bodies were built on the new B-body that lasted until 1996. The A-body designation would be resurrected by GM in 1964 for a new series of intermediate-sized cars including the Chevrolet Chevelle, Pontiac Tempest, Oldsmobile Cutlass and Buick Skylark.

The GM B-body was introduced in 1926, and had at least 12 major re-engineering and restyling efforts, in 1937, 1939, 1941, 1949, 1954, 1957, 1959, 1961, 1965, 1971, 1977, and 1991; along with interim styling changes in, 1942, 1969 and 1980 that included new sheetmetal and revised rooflines. The platform was downsized in length by approximately 10 inches in 1977 and reduced in weight by an average of 800 pounds. In 1991, the platform received its last major redesign, regaining several inches in length, numerous frame improvements and reinforcements, while the shorter wheelbase remained unchanged. The last B-cars rolled off the line in 1996, leaving only Ford producing domestic large rear wheel drive sedans until the line was phased out in late 2011, with Chrysler reentering the market with their LX platform in 2005.