The deal was made two days before Johnson attempts to claim an unprecedented fourth straight Sprint Cup title at Sunday's season-ending Ford 400 at the Homestead-Miami Speedway in Homestead, Fla.
He needs to finish 25th or better to beat Mark Martin for the 2009 Sprint Cup championship.
"Jimmie is charting new territory in our sport, and that's due to a combination of natural talent and unsurpassed work ethic," team owner Rick Hendrick said. "There's no question that he's one of the great champions in all of sports, and he's not done yet."
Also Friday, Lowe's, the primary sponsor of Johnson's No. 48 Chevrolet, signed a contract extension through 2013.
Copyright 2009 by United Press International.
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