Hamlin crew chief Darian Grubb and car chief Wesley Sherrill were suspended for six weeks and put on six months' probation by NASCAR after the Joe Gibbs Racing car failed a post-race inspection at Indianapolis Motor Speedway. Grubb also was slapped with a $125,000 fine.
NASCAR's inspection uncovered problems with the rear firewall in the driver compartment that could create more downforce. The P5 penalty, as determined by a NASCAR scale, is considered "extremely serious."
The suspensions run through the Sept. 6 race at Richmond. Neither Grubb nor Sherrill will be able to return until the first race in the Chase for the Championship on Sept. 14 in suburban Chicago.
Joe Gibbs Racing said Tuesday that it plans to file an appeal, but both Grubb and Sherrill will start serving the suspensions immediately.
Hamlin finished third in the race won by Jeff Gordon. Hamlin also was stripped of 75 points and dropped from 11th to 22nd in the season standings. But the lost points will have little impact on Hamlin's Chase for the Championship after he all but secured a spot with a win at Talladega in May.