The most successful turnaround of the teams I examined was arguably turned in by Jerry Claiborne with Maryland. He raised the winning percentage by 53.5%, the biggest such gain and notched 3 conference championships within his first five years, the most of any on the list. In the five years prior to Claiborne being hired, the Terrapins has posted just 9 wins in 51 games (.176); in the first five years under Claiborne, they won 41 and tied 2 of 59 games (.712), and in addition to those three conference titles, they also went to four consecutive bowl games (a streak that would stretch to six). By any measure, this was a dramatic and impressive turnaround.
Maryland has had a mostly modest history in football. For much of their first 50 or so years playing the sport, they churned through coaches without a great deal of success; most coaches were there less than four seasons. The notable exception was Curley Byrd who coached 24 seasons (still a Maryland record), winning 58.6% of their games, but there were no conference championships or bowl games under his watch.
Included in that churn of coaches were Clark Shaughnessy (in 1942 & 1946) and Bear Bryant in his first head coaching job. He left after just one year due to conflict with the school president. Major success finally came to Maryland in the form of Jim Tatum. In his nine years at the helm, Maryland posted a remarkable 73-15-4 (.815) record, including being crowned National Champs in 1953 by the AP & UPI (this was in the era when the final polls happened before the bowl games). When Tatum departed for his alma mater North Carolina, the Terrapins settled back into mediocrity - and then much worse. Enter Claiborne.
Claiborne played halfback at Kentucky under Bear Bryant, and went directly into coaching after college. After a few years with the Augusta Military Academy, he joined Bryant as an assistant, first at Texas A&M and then at Alabama. He then got his first head coaching job with Virginia Tech, posting a 61-39-2 (.608) record. As an indication of VPI's place in the college football universe at the time, he left for an assistant coaching position at Colorado in 1971 before Maryland came calling and hired him to be their head coach in 1972.
Situations were not ideal at Maryland - besides the poor results that had killed any positive reputation the Terrapin program had, their facilities were subpar - they lacked a sufficiently large room for team meetings, and the weight rooms were so small many players had to lift weights outside.
Claiborne was very much influenced by his time with Bryant. His offenses were conservative, and he relied on terrific defense and molding tough players. He also had a good portion of Bryant's ability to immediately turnaround a program - in his first year, following successive 2-9 campaigns, he guided Maryland to a 5-5-1 record. That would prove to be the least successful season he had with the Terrapins until his final season there in 1981. In his second season he lifted Maryland to 8-4 and the first of six consecutive bowl games. Things continued to improve, and in his third season he won the first of three consecutive ACC championships. The peak of his tenure was his fifth season when Maryland went 11-1 with their only loss coming in the Cotton Bowl vs. the #6 ranked Houston Cougars. The loss eliminated any chance of the #4 ranked Terrapins of claiming another National Championship.
Claiborne continued to have success at Maryland, ultimately appearing in seven bowl games and posting a 77-37-3 (.671) record, but no further ACC titles. After his only losing season at Maryland (4-6-1) in 1981, Claiborne jumped at the chance to coach Kentucky, his alma mater. Kentucky had been plagued by recruiting violations under Fran Curci, and Claiborne had a tough go in his first year, finishing 0-10-1. But by his third year with the Wildcats he had lifted them to 9-3 and a bowl game. His final five years were a study in consistent mediocrity, going 5-6, 5-5-1, 5-6, 5-6 & 6-5 before retiring after the 1989 season.
Claiborne was known not just for his teams' success on the field, but also in the classroom, and was consistently praised by his employers, players and peers as a coach that did things the right way.
Taking over for Claiborne at Maryland was a then little-known Bobby Ross. It was at Maryland that Ross first established his own reputation as a great coach, nearly matching Claiborne by posting a 39-19-1 (.669) record in five seasons, winning three ACC titles of his own with four bowl game appearances. When Ross then left for Georgia Tech in 1987 (where he would win a split National Championship in 1990), Maryland fell into a tough stretch of poor play until hiring Ralph Friedgen in 2001. Friedgen, a Maryland alum and former assistant under Ross found immediate success, posting 10-2, 11-3 & 10-3 seasons in his first three seasons. He was unable to sustain that success, and ultimately was fired in a messy way after the 2010 season despite a 9-4 record. Friedgen's successor Randy Edsall finds himself already on a very hot seat entering his third season after posting 2-10 & 4-8 records to start his Maryland career.