General Motors uses letter codes to signify which chassis layout, or body type, the vehicle has. This is useful since GM consists of many different makes such as Chevrolet, Oldsmobile, Pontiac, Buick, and Cadillac. Many of these brands share platform types with each other. It isn’t some secret, alphabetic code that GM fans are privileged to. It is really quite simple. Each platform has changed somewhat over the years so we’ll walk through them in more or less chronological order.
The Early Years
GM started with just four platforms: the A, B, C, and D bodies. In the beginning, A and B were both for full size cars. A body models included the Chevy Superior, the Oldsmobile 60, and most Pontiacs. The B Body was used for the Buick Century among others. GM decided it didn’t make sense to have two platforms for full size cars so the A body was discontinued and the B Body became the standard for full sized cars in 1959. GM continued to use the B body designation for full size, rear-wheel drive cars until 1996. The Chevy Bel Air, Buick LeSabre, Chevy Impala, and Pontiac Bonneville were all built on the B body platform in this era.
In 1931, GM Introduced the C body. The C body would continue as a long wheelbase RWD car until 1984. The C body was essentially a lengthened version of the B body. The Pontiac Torpedo, Buick LaSalle, and Oldsmobile 90 were built on this platform.