GMC Sierra I (GMT400) gallery (1988–1999)
The first standalone generation of the full-size GMC Sierra pickup truck based on the GMT400 platform with independent front suspension.
The first official generation of the GMC Sierra as a standalone full-size pickup truck debuted for the 1988 model year on General Motors' advanced GMT400 platform, replacing the previous boxy C/K generation. It introduced an aerodynamic body style, an all-welded ladder frame, galvanized steel body panels for corrosion resistance, and an independent front suspension that dramatically improved ride comfort compared to traditional solid-axle designs. Available body configurations included two-door Regular Cab, Extended Cab with rear jump seats, and four-door Crew Cab across 1500, 2500, and 3500 series with standard Wideside and flared Sportside beds. The powertrain lineup featured a 4.3-liter Vortec V6, small-block 5.0-liter and 5.7-liter V8 engines, a massive 7.4-liter big-block V8, and 6.2-liter or 6.5-liter Detroit Diesel V8 engines. Transmissions included five-speed manual units and heavy-duty four-speed automatic gearboxes like the 4L60E and 4L80E. In 1995, the Sierra received a completely redesigned passenger-friendly interior with rounded controls and standard airbags, followed by the introduction of upgraded Vortec engines with sequential fuel injection in 1996. The vehicle was primarily marketed and sold across North America and select Middle Eastern regions.
