United Auto Workers members overwhelmingly approved a new three-year contract with General Motors Corp. that protects union jobs while freeing GM to seek looser work rules, the UAW announced Sunday night. UAW members at 152 locals nationwide voted 80.7% in favor of the agreement, said UAW spokesman Frank Joyce. About half the union's 330,000 members at GM cast ballots, he said. GM has been notified of the ratification, which means the contract takes effect today. The agreement, like one at Ford Motor Co., forbids layoffs for most reasons except cuts in production volume because of slow sales. It also increases wages 3% the first year, pays 3% lump-sum bonuses in the second and third years, sweetens retirement benefits and requires the company to hire or recall one worker for every two who leave.