"Major redesign" refers to making significant changes or improvements to something, often involving a complete or substantial overhaul in its design, appearance, or functionality. Full definition
The 2017 model, though, is the first major redesign of the vehicle. (prestigeimports.net)
This is the first major redesign in the vehicle's history. (kbb.com)
The Avalon received its last major redesign for the 2012 model year, and enters 2015 without any changes to its still - contemporary exterior design. (Autoweek.com)