The 2015 to 2023 Mustang GT, code-named "S550," continued on from the Fifth Generation Mustang GT but featured updated styling, greater performance, and, most notably, the introduction of independent rear suspension. The GT Fastback Coupe and GT Premium Convertible grew in size with more prominent fenders but featured a sleeker profile, as well as a redesigned interior. Dynamic improvements included upgraded front-end suspension components, with a stiffer subframe benefiting handling steering and ride quality. Ford transitioned from a solid rear axle to a rear independent system with advanced stability control for the first time to compete with other modern performance vehicles. The 5.0L Coyote V8 engine saw upgrades through the generation, and power varied between 435 hp and 450 hp. Power was sent to the rear wheels through a six-speed automatic or manual transmission with a ten-speed automatic joining in 2018. An optional GT Performance Pack added larger Brembo brakes, heavy-duty suspension components, unique chassis tuning, a larger radiator, and a TORSEN rear differential. The Shelby GT350, GT500, 50 Year Limited Edition, Bullitt, Petty's Garage, and Mach 1 were based on the GT platform with different VIN numbers.