McClanahan attended Mounds View High School and went on to play three seasons with the University of Minnesota, winning the 1979 NCAA national ice hockey championship. After representing the U.S. at the 1979 Ice Hockey World Championship tournament in Moscow, McClanahan joined the U.S. Olympic team on a full time basis and scored 34 goals in 63 exhibition games. The culmination of McClanahan's amateur career came at the 1980 Olympics in Lake Placid, New York when he scored five goals in seven games while helping his country win the gold medal. He scored the winning goal in the gold medal game against Finland (which the U.S. came back to win 4-2) two days after the historic American victory over the Soviets.