The first generation of GMC Sierra was introduced for the 1988 model year. The Sierra name had been previously used for GMC's top trim level, but in 1988, the Sierra became its own model. The first generation of Sierra was built on the GMT400 platform and was available in standard cab, extended cab, and crew cab configurations. One V6, or three V8 engine options were available for the first generation Sierra, which was built until 1999, and replaced by the Second Generation GMC Sierra. Although production of the standard 1st Gen Sierra ended in 1999, the heavy duty models remained in production until 2002.