GM B platform

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

As a body designation, B-body production began in 1959, when General Motors restyled and redesigned all of its standard-sized and luxury cars - the first time in GM's history that such had been accomplished in the same year. From the late 1940s until 1958, GM used three different designations for various bodyshells/platforms including the A-body for Chevrolets and Pontiacs, B-body for Oldsmobiles and the smaller Buicks, and C-body for the larger Buicks and all Cadillacs. For the 1959 and 1960 model years, all GM standard-sized and luxury cars used the same basic B-body platform with a stretched version of that platform called the B-plus body for all Cadillacs as well as Buick Electra and Oldsmobile 98. For 1961, the B-plus body was rechristened the C-body for all Cadillacs as well as the top-line Buicks and Oldsmobiles, while the B-body designation continued for all other standard-sized cars including all full-sized Chevrolets and Pontiacs, the Oldsmobile 88 and Buick's LeSabre and Invicta models. 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 had at least 5 major re-engineering and restyling efforts, in 1959, 1965, 1971, 1977, and 1991; along with interim styling changes in 1961, 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. The last B-cars rolled off the line in 1996, leaving only arch-rival Ford producing large rear wheel drive sedans. Today, however, the situation looks to reverse, with Ford switching to front wheel drive for most cars and GM reintroducing rear wheel drive with their new Sigma platform. Chrysler has also reintroduced rear wheel drive with their new LX platform.

Most B-body cars used suspensions utilizing coil springs both front and rear, including all B-body cars from 1961 to 1970 and again from 1977 to 1996. Exceptions include the 1959-60 Oldsmobile 88 and 98, and the 1971-76 station wagons from all four GM divisions, both of which used coil springs in front and multi-leaf springs in the rear. All B-body cars since 1965 have used perimeter frames with side rails, along with the 1961-64 B-body Pontiacs and Oldsmobiles. The 1959-60 Buicks used a ladder-type frame while an X-frame without side rails was used on 1959-60 Pontiacs and Oldsmobiles, 1959-64 Chevrolets and 1961-64 Buicks.

The B-body was the last platform design to have the gasoline tank filler port behind the license plate. Exceptions included all station wagons, as well as all 1961-64 cars - which had the tank filler in the rear fender on the driver's side.

Most B-body cars were replaced by H-bodies.

Sedans built on the B platform include: