in two World Endurance Championship races, coming 21st at the Nürburgring 1000km for Obermaier Racing in their Porsche 956 and finishing 5th in the 956 of Kremer Racing at the Fuji 1000km. Thackwell finished the 1984 season in CART for Penske Racing, in their Pennzoil March 84C, after foot injuries at Sanair during practice for the Molson 300 sidelined Penske ace Rick Mears. While not scoring any points in his two races, unlike Johnny Rutherford, who raced the first two races of Mears' eventual year and a half recovery as a substitute, the #6 team finished third overall in the 1984 season. Unable to get a decent drive in F1 and CART, he turned his back on them and raced in the F2 replacement series, the Formula 3000. He won the first round at Silverstone and in the process, won his third International Trophy race. He added two victories before finishing runner-up to Christian Danner. Meanwhile, he also raced four times for the TWR Jaguar team, rounding his season off with a second place at the Shah Alam circuit, partnered by John Nielsen. In 1986 he continued to win in F3000, both in Europe and Japan, and scored Mercedes-Benz's first modern racing success when he shared a Sauber with Henri Pescarolo to win the Nürburgring 1000km. During the European winter of 1987, Thackwell returned to New Zealand to race in Formula Pacific. He won the first three rounds of the MANZ Formula Pacific International Championship, going on to take the title. He concentrated on sports car racing with the Kouros Racing Team in their Sauber C9 in 1987, only to receive yet more disappointment. His only podium finish in the World Endurance series came after he quit and took a drive with Britten Lloyd Racing in their Porsche 962GTi, this time partnering Mauro Baldi. In 1988 he had a one-off F3000 drive for the works Ralt outfit at Pau. However, having become disillusioned with motorsport, he turned his back on it at the end of 1988. In the years following his withdrawal from motorsport, he worked, among other occupations, as a helicopter pilot in the North Sea for British International Helicopters, a gold miner in the North-West of Western Australia and as a teacher in England. He is widely felt to have been one of the great 'lost talents' – a driver in the wrong place at the wrong time.