From 1976 on, he was a factory driver for Porsche and their new turbocharged race cars, the 935 and especially the 936 sports car, which he drove to wins in Le Mans three times.
A partir de 1976, foi un piloto de fábrica de Porsche e dos seus novos coches turbo de carreiras, o 935 e, especialmente, o coche deportivo 936, o cal levou a vitoria en Le Mans tres veces.