NASHVILLE, Tenn. - The son of a Texaco truck driver from Bridgeport, Connecticut, actor John Ratzenberger has always had a strong affinity for the industry. So after he became famous as voluble mailman Cliff Clavin in the 1980s sitcom "Cheers" and voicing Hamm the Piggy Bank in the animated "Toy Story" movies, it was natural for Ratzenberger to lend his vocal talents to a truck in "Cars," another Pixar film.