A prosperous driver whose father was killed during the war, Posey made quite a reputation on the North American scene as a versatile Formula 5000 and Trans-Am saloon competitor. He had two Surtees Formula 1 drives, in the 1971 and 72 US Grands Prix, and later shared the 1975 Sebring 12-hour winning BMW CSL with Brian Redman, Alan Moffat and Hans Stuck.
Posey has appeared at the 24 Hours of Le Mans 9 times and finished in the top 10 5 times. His best finish was during the 1971 in which he drove the Ferrari 512M.
Posey went on to become an auto racing commentator for ABC Sports. While commentating the 1986 Indianapolis 500, as there was a yellow flag out near the end of the race, Posey would use a two way radio to ask an impromptu question to race leader Kevin Cogan. Posey was asking Cogan about his thoughts about leading the Indianapolis 500 at this stage. Cogan would politely reply to Posey that he was "busy now", but would talk to him later. Posey understood the circumstances and told the audience if that was him, "I wouldn't want to talk to me either".
In 1989 Posey was brought in as part of the ABC Sports broadcast team covering the 1989 Tour de France. Many people were surprised by Posey's knowledge and genuine enthusiasm for the sport. ABC would bring him back as the lead anchor for the 1990 and 1991 races.
Posey would then move to Speedvision (now known as SPEED Channel) He currently does essay work for Outdoor Life Network's coverage of the Tour de France serving as the "Race Historian".
Posey suffers from Parkinson's Disease.
Posey is also the author of Playing With Trains, a book on model railroading published by Random House and "The Mudge Pond Express" an autobiography which centers around his personal racing career and love of the sport.