The University of Michigan said Kramer died Saturday at his home. It did not release the cause of death.
Kramer caught two TD passes from Bart Starr in Green Bay's 1961 NFL championship victory over the New York Giants. He had his most productive season in 1962 with 37 receptions for 555 yards and seven touchdowns and was an All-Pro.
Kramer spent seven seasons with the Packers after being drafted in the first round with the fourth overall pick in 1957. He did not play in 1958, when he joined the Air Force while recovering from a leg injury suffered at the end of his rookie season. He finished his career with three seasons in Detroit, retiring after the 1967 season.
Kramer earned three letters each in football, basketball and track at Michigan and led the Wolverines in scoring for two seasons in football.
His No. 87 is one of just five numbers retired by the school in football. He played offensive and defensive end, running back, quarterback, kicker and receiver.
"He called me after every loss, and that meant a lot because it's a lonely feeling to lose when you're the coach at Michigan," former Wolverines coach Lloyd Carr said Saturday night. "I'll never forget that he used to bring our team apples because he remembered somebody doing that for him when he played at Michigan."
As a basketball player, Kramer scored 1,119 points and was the team's Most Valuable Player as a junior. He set the school's all-time scoring record as team captain his senior year with 1,124 points, a standard that stood until 1961.
Despite his 230-pound frame, he competed in the high jump in track.
"Ron was one of the great Michigan athletes of the 20th century," Michigan athletic director Dave Brandon said in a statement released by the university.
After retiring, he operated Ron Kramer Industries in Fenton, Mich., about 35 miles north of Ann Arbor.
Kramer was elected to the Michigan Sports Hall of Fame in 1971. In 1981, he was named a recipient of the NCAA's Silver Anniversary Award in recognition of significant professional and civic contributions spanning 25 years after completion of his collegiate eligibility.
He was born June 24, 1935, in Girard, Kan., and his family moved to the Detroit area when he was 5.
Details on funeral arrangements weren't immediately available.