Troxel's entry into drag racing came through hands-on work with her father's race team, where she developed the mechanical understanding and competitive instinct that would define her career. She progressed through the ranks to reach the elite Top Fuel category, where nitromethane-fuelled dragsters regularly exceed 300 mph.
Troxel's defining year came in 2006, racing Top Fuel for Don Schumacher Racing. She became the first driver in NHRA history to appear in five consecutive championship finals within a single season, winning two of them. In the course of those races she set the sport's speed record at 332.51 miles per hour (535.12 km/h) and the elapsed-time record at 4.458 seconds — benchmarks that underlined both her performance and the quality of equipment she was driving. The Women's Sports Foundation recognised the achievement by naming her Individual Sportswoman of the Year for 2006.
After losing her sponsorship at Don Schumacher Racing, Troxel joined Morgan Lucas for the 2007 season and added two further Top Fuel victories to her record before a further change in circumstances.
In 2008 she made the switch from Top Fuel to Funny Car, joining an operation owned by Mike Ashley that was sold to Roger Burgess before the season began. The transition was rocky early in the year, with four non-qualifications in the first six races, but she recovered to win an event during the season — becoming the first woman to win a Funny Car race, two events after Ashley Force had won in the same category. With that Funny Car win added to her Top Fuel victories, Troxel became the only woman to have won races in both of NHRA's most prestigious categories.
For 2009, Troxel raced in the Pro Modified class with R2B2, a category that was operating on an exhibition basis at the time. In 2010 she continued racing Pro Mods while fitting in selected Funny Car appearances at events in different locations on the same weekends. During her Pro Modified campaigning she set the NHRA Pro Modified run record of 5.772 seconds.
In 2015 she was recruited to pilot an electric drag racer for Don Garlits, the legendary Top Fuel driver who had turned his attention to electric propulsion in his later years.
Troxel was married to fellow drag racer Tommy Johnson Jr. between 2003 and 2009.
Melanie Troxel's career is defined by firsts. First to reach five consecutive championship finals in a season, first woman to win in Funny Car, and the only woman to have taken victories in both Top Fuel and Funny Car — the two highest-profile classes in the sport. Her 2006 season speed record of 332.51 mph and elapsed-time mark of 4.458 seconds placed her at the absolute frontier of drag racing performance, and her recognition by the Women's Sports Foundation placed her alongside elite athletes across all of American sport for that year.