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Dale Earnhardt Jr. and his manager, sister Kelley Earnhardt Elledge, answer questions at a news conference Thursday.

updated 8:52 p.m. ET May 10, 2007

MOORESVILLE, N.C. - For Dale Earnhardt Jr., winning is everything. That’s what his daddy taught him.

And by ditching his namesake company to find a more competitive ride, Junior gave his own lesson in life: Not even blood is thicker than winning.

NASCAR’s most popular driver ended months of contentious contract negotiations with his stepmother Thursday, announcing he will leave Dale Earnhardt Inc. at the end of the season because he and Teresa Earnhardt can’t agree on a common vision for the family business.

“It is time for me to continue his legacy in the only way I know I can — by taking the life lessons that he told me: Be a man, race hard and contend for championships,” Junior said. “That’s what I intend to do, and I feel strongly that I would have my father’s blessing.”

Earnhardt had tried to reach a new deal with his stepmother. But the bargaining turned tense after she publicly questioned his commitment, and Junior later said their relationship “ain’t a bed of roses.”

So he’ll move on, starting what should be a frenzied free agency period that could shake the sport by causing long-term ripple effects in driver salary and sponsor deals.

He’s already NASCAR’s highest-paid driver, earning $20.1 million per year, a million more than No. 2 Jeff Gordon.

And the bidding has already begun.

“704-662-9642, tell him that’s my phone number,” said car owner Chip Ganassi, who lured Juan Pablo Montoya away from Formula One this season to drive one of his Dodges.

Perhaps Teresa Earnhardt should shout out her phone number, too, now that she must rebuild the company without its star.

“While we are very disappointed that Dale Jr. has chosen to leave the family business, we remain excited about our company’s future,” she said in a statement. “Dale and I built this company to be a championship contender, and those principles still apply. Dale Earnhardt Inc. will win.”

The late Dale Earnhardt started DEI in 1980 as a little company he hoped to someday hand over to his four children. DEI had grown into one of NASCAR’s elite teams when Earnhardt was killed on the last lap of the 2001 Daytona 500, but it slowly has deteriorated since. The team currently fields cars for Earnhardt, Martin Truex Jr. and rookie Paul Menard.

Despite 17 career victories, Junior has never been a consistent championship contender. He flirted briefly with the title in 2004 but had a horrendous 2005 season, when his stepmother split up his crew and he finished a career-worst 19th in the standings.

Earnhardt rebounded slightly last season, when he made the Chase and finished fifth. He’s yet to show any muscle this season, with three top-10 finishes through 10 races.

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“At 32 years of age, the same age my father was when he made his final and most important career decision, it’s time for me to compete on a consistent basis and contend for championships now,” he said.

Earnhardt agonized over the decision and said telling DEI’s employees on Thursday morning was one of the hardest things he’s done. Underneath his party-boy persona, Junior cares terribly what people think and worries his father’s fans will feel betrayed by this defection.

It’s why he asked Darrell Waltrip, a friend and former rival of his father’s, to fly in from Nashville.

His mother, Brenda Jackson, said her son struggles to understand his place in the sport.

“He never wants to upset anybody,” she said. “As long as Dale Jr. is racing, the Earnhardt legacy is alive.”

Earnhardt strongly believes his father’s vision for DEI has been lost, and it’s why he demanded 51 percent of the company during contract negotiations that started before the season began. His sister, Kelley Earnhardt Elledge, had set a deadline to get the deal done by the end of the month.

“We never even got close,” he said. “It’s not the guy who gives me the biggest paycheck. There’s some things you can’t get with money — peace of mind and satisfaction in what you do everyday.

“I’m seeking to have that peace of mind and that comfort to be able to really be an asset to somebody. I want to go somewhere and really make things happen for somebody.”