Yet the penalties did not appear severe enough to dent Hamlin's chances of qualifying for NASCAR's Chase for the Sprint Cup title playoff that starts Sept. 14.
Hamlin finished third in Sunday's Brickyard 400 at Indianapolis Motor Speedway. After the race, NASCAR said it had confiscated rear firewall block-off plates from Hamlin's car.
NASCAR said Tuesday that the improper plates effectively allowed for unapproved air flow through Hamlin's car that could improve its aerodynamics.
NASCAR docked Hamlin 75 championship points, dropping him to 21st from 11th in the Cup standings.
In addition, Hamlin's crew chief, Darian Grubb, and car chief Wesley Sherrill were suspended for the next six races, and Grubb was fined $125,000.
Gibbs said that it would appeal the penalty but that Grubb and Sherrill would start serving their suspensions, beginning with this weekend's race at Pennsylvania's Pocono Raceway.
There are six races left before the Chase begins at Chicagoland Speedway. So by starting their suspensions now, Grubb and Sherrill will be able to return for the start of the 10-race playoff.
And because NASCAR changed the Chase rules this season to put a greater emphasis on drivers' winning races to qualify for the playoff, Hamlin's Chase berth probably remained intact despite the penalties.
A win during the regular season virtually assures a driver will make the Chase, and Hamlin already has one victory this season, at Talladega, Ala., on May 4.