Castaing was responsible for product engineering and development at AMC. He was instrumental in the development of the downsized Jeep Cherokee, a sport utility vehicle (SUV) that became very profitable for AMC and thereby instigated what would become the modern SUV era. As AMC's Vice President for Product Engineering and Development, he also designed a new development approach in which teams of engineers focused on a single type of car platform, working on new models as a system from concept to production. The automaker was looking for a way to speed up its product development process to compete better against its larger competitors in 1985. This differed from the traditional automotive practice of organizing work around departments (such as project planning, design, engineering, manufacturing, and marketing) and components (such as engine, powertrain, and body).