Considering Le Mans and sports cars too dangerous after the deaths of Manfred Winkelhock and Stefan Bellof, he was recruited for the 1987 World Touring Car Championship for Ford only to finish runner-up by a single point to BMW driver Roberto Ravaglia after a post-season disqualification (after Ludwig claimed the pole, he and fellow West German Klaus Niedzwiedz had finished second behind teammates Steve Soper and Pierre Dieudonné at the Bathurst 1000 in Australia, but both cars were disqualified due to illegal wheel arch size on their Ford Sierra RS500s).

He repeated the success at Mercedes-Benz in 1992 and 1994, before moving back to sports cars racing for them in 1997 to become the 1998 FIA GT Champion.

When the DTM resumed as Deutsche Tourenwagen Masters in 2000, he returned to the series, winning at the age of 50 years at the Sachsenring circuit, only to retire once again.

Ludwig returned as a "hobby pilot" to the Nürburgring Nordschleife when given the opportunity to drive a high power vehicle.

With a normally aspirated Porsche 997 GT3 of the Alzen brothers, Ludwig and Christian Abt managed to beat the old distance record in the 2006 edition of the 24h, yet finished only second, 1 lap behind the winners.