He also attempted a 410 Sprint Car competition at the Knoxville Nationals, where he failed to qualify. In 2007, Walker returned once again to NASCAR competition. This time, he re-joined the Craftsman Truck Series and was slated to drive the #36 360 OTC Toyota Tundra for Bill Davis Racing full-time. His truck was painted in a matter similar to Nextel Cup teammate Jeremy Mayfield, who also carried 360 OTC sponsorship. Incidentally 360 OTC was a prior title sponsor of the World of Outlaws where Walker had toiled for so many years. In addition, the World Wrestling Entertainment and the rock band Kiss served as associate sponsors to complement the entertainment package sponsorship. Walker had three top-six qualification efforts, including a career best 2nd-place start Kansas Speedway. His best finish came at the tricky and legendary Martinsville Speedway, where he finished in the ninth position, his only career top-ten finish in NASCAR competition. After 6 races it was announced that Ryan Mathews would drive part-time sharing the ride with him. Walker was suspended indefinitely by NASCAR on May 18, 2007, for violation of the substance abuse policy, and has not competed in NASCAR since. Recovery and relapse (2007–2012) Following his abrupt suspension from NASCAR, Walker spent the next several months out of racing. He returned to competition in the USAC Series at the famed Copper World Classic at Phoenix International Raceway, finishing eighteenth in the final overall running order. He attempted several races in 2008 in the World of Outlaws Series in the #24T entry, but failed to qualify for many of them, and only getting one top-ten finish, a ninth-place finish, at Manzanita Speedway. Walker did achieve victory in a heat race in the Mini Gold Cup at the Silver Dollar Speedway. He also ran a USAC race for RFMS at Terre Haute Action Track and finished 19th. Walker made limited appearances in the USAC Silver Crown series in 2009 with the #23 Vance Racing team. His ultimate result was a fifth that came on July 23 at Indianapolis Raceway Park. Walker was contracted to drive the Mike Heffner #27 entry in Pennsylvania to start the 2010 season in various sprint car series. After decent finishes, he left the Heffner car, and was hired by Keen Motorsports to race the 17 Peterbilt sponsored car in 2011, primarily concentrating in 410 Sprints. By switching rides, Walker traveled out of Pennsylvania to