 In 1975 Leffler stepped up to the Australian Drivers' Championship (the "Gold Star") and driving a Bowin P8 Chevrolet finished fifth in the series.The following year he secured the 1976 Australian Drivers' Championship title in a Lola T400 with a string of consistent placings but without actually winning a round.Leffler also co-drove for some of the leading Australian touring car drivers in endurance events.