General Motors Co reported on Monday its biggest drop in China sales in five months for August as global automakers struggle with a deepening economic slowdown and slumping equities in the world's largest auto market. Vehicle sales for GM and its joint venture partners fell 4.8 percent year-on-year in August, while Ford Motor Co and Nissan Motor Co Ltd also reported contracting sales for the month, highlighting the divide between winners and losers in the Chinese market.