GMT-400 was General Motors’ internal full-size truck platform for GMC’s late-1980s and 1990s light-duty and sport-utility vehicles. It marked the modernizing of the brand’s traditional body-on-frame pickup and utility lineup, bringing a more aerodynamic cab and updated chassis design to the familiar GMC truck formula. For GMC, the architecture underpinned the era’s full-size pickup family and related truck-based utilities, including the long-running Yukon and Suburban derivatives built from the same basic engineering family.
The platform arrived for the 1988 model year and became one of the most important truck foundations in GM history, carrying GMC through the end of the 20th century. While the pickup side of the lineup moved to the next-generation GMT800 at the end of the 1990s, some GMT-400-based utility and heavy-duty variants continued into the 2000 model year before the platform was fully retired. Enthusiasts often associate it with the classic “old body style” GMC trucks that bridged the gap between the square-body era and the modern Sierra/Yukon lineage.