Harrison arrived at United in 1981 as a youth coach and was the academy director when the Class of 92' broke through into Ferguson's first team.
"Eric's contribution to football and not just at Manchester United was incredible," said Ferguson.
"When I came as manager, I was lucky enough to have Eric on the staff as head of youth development, so I got to see the work he did and not just with the Class of '92 but with all the young players.
"He built character and determination in those young players and prepared them for the future.
"He was a teacher, he gave these players a path, a choice and he only did that through his own hard work and sacrifice.
"He was able to impart that education to the young which made him one of the greatest coaches of our time."