The relationship with Ferrari deteriorated during 1937, and Nuvolari raced an Auto Union in that year's Swiss Grand Prix. He rejoined the Auto Union team for the 1938 season and stayed with them through 1939 until Grand Prix racing was put on hiatus by World War II. The only major European race he never won was the Czechoslovakian Grand Prix.
The relationship with Ferrari deteriorated during 1937 and Nuvolari raced an Auto Union in that year's Swiss Grand Prix He rejoined the Auto Union team for the 1938 season and stayed with them through 1939 until Grand Prix racing was put on hiatus by World War II The only major European race he never won was the Czechoslovakian Grand Prix