Michigan announced on Saturday that Johnson had died after a long battle with Alzheimer's disease. He was in an assisted living facility in New Jersey.
Johnson was an All-American for the Wolverines in 1968 when he set a school record that still stands with 347 yards rushing against Wisconsin. He ran for 1,391 yards that season and scored a school-record 19 touchdowns, another record that still stands.
Johnson was drafted by Cleveland in the first round in 1970 and was traded to the Giants the following season. He became the first Giants player to run for 1,000 yards in a season in 1970 and accomplished the feat against in 1972. He finished his career in 1975.
Johnson was inducted into the College Football Hall of Fame in 1992, and became the chairman of the National Football Foundation, which runs the Hall of Fame, in 2006.
In 2008, he was diagnosed with Alzheimer's disease. He is survived by his wife, Karen.