Details of the agreement will remain under wraps,  Teamsters Local 399 business agent Steve Dayan said today, until the membership approves or rejects the deal. The Los Angeles branch of the union, which reps about 300 of the 500 or so casting directors and associates, will vote on September 15. No official word on when Local 817, the New York branch, will vote, but the same date is likely. The current three-year collective bargaining agreement expires September 30. The union’s new deal with the Alliance of Motion Picture and Television Producers, achieved in just four sessions of negotiations, would be the third between the studios and casting directors, who organized under the Teamsters banner in 2005.