After retiring as a player, Gilmer became an assistant coach with the Pittsburgh Steelers under Parker in 1957. After four years there and four with the Minnesota Vikings under Norm Van Brocklin, he succeeded George Wilson as Lions head coach in January 1965.
After retiring as a player, Gilmer became an assistant coach under Parker in 1957. After four years with the Pittsburgh Steelers and four with the Minnesota Vikings under Van Brocklin, he succeeded George Wilson as Lions head coach in January 1965.