August he left Green Light Racing, and on the 20th announced he would drive for MRD Motorsports replacing Blake Bjorklund with The GPS Store and Garmin coming with him to sponsor the No. 8. With The No. 8 team, he scored his first top ten of the year at Las Vegas. McCumbee took the truck to a near upset victory at Texas before spinning his tires on a restart which led to being wrecked while leading with two laps to go and he finished 13th. On 2 May 2007, Petty Enterprises announced McCumbee would make his NEXTEL Cup debut, filling in for Kyle Petty while he was in the TNT broadcast booth, for one race at Pocono on 10 June 2007 in the Pocono 500. Goody's Cool Orange Headache Powders sponsored the car, and McCumbee finished 25th in that race. Petty tabbed him again for Michigan in the 3M Performance 400 because of Petty's broken hand. Clutch problems after a spin and forced the team behind the wall for more than fifty laps resulting in a 41st-place finish. He also won his first two ARCA races, at Nashville Superspeedway and Pocono Raceway respectively, driving for Andy Belmont. McCumbee started the 2008 season with a 7th at Daytona, and had a then career-best finish of 5th at Atlanta, before picking up his career best finish of 2nd place at Charlotte in the Malcomson Construction truck. He ended the season 11th in the points standings. He also continued to run part-time for Petty's No. 45 entry with Marathon American Spirit Motor Oil sponsoring, making a total of six starts but failing to qualify on three occasions. His best finish was 17th at Pocono. He was the top choice for Kyle Petty's replacement in the 45, and signed a contract to drive for Petty full-time in 2009. A deal was made to merge Gillett Evernham Motorsports and Petty Enterprises which formed Richard Petty Motorsports, and as a result, McCumbee lost his Sprint Cup ride. For the 2009 Camping World Truck Series Season, McCumbee rejoined SS-Green Light Racing to be driver of the No. 7 Chevy with sponsorship from ASI Limited and The GPS Store. He had two top-ten finishes early in the season, and despite funding from Tiwi and Valvoline, he was replaced for four races during the season by other drivers bringing funding, and fell to nineteenth in points. He reunited with