The occasions when the world champion has left the team:
1979 Waldegård with Ford (and Mercedes) --> 1980 to Mercedes, Fiat and Toyota
1981 Vatanen with Ford -- 1982 to private Ford (because Ford works team didn't run in 1982)
1982 Röhrl with Opel --> 1983 to Lancia
1986 Kankkunen with Peugeot --> 1987 to Lancia (because Peugeot didn't continue in Group A)
1987 Kankkunen with Lancia --> 1988 to Toyota
1992 Sainz with Toyota --> 1993 to Lancia
2001 Burns with Subaru --> 2002 to Peugeot
2016 Ogier with VW --> 2017 to M-Sport (because VW quit)