A factory in Vienna has produced the 20-millionth gearbox for General Motors (GM), it emerged today (Thurs).GM Powertrain Austria boss Rudolf Hamp said GM decided to pour an additional 50 million Euros in the plant in Donaustadt district to improve the production process after the 20-millionth gearbox left the conveyor belt earlier this week.Hamp said in March 2010 two-digit growth rates were possible for the coming years after GM struggled in 2009.Smaller fuel engines and gear mechanisms are produced in the Powertrain factory. Around 90 per cent of its production is delivered to GMs German subsidiary Opel and British sister firm Vauxhall. One in two Opel cars have a transmission and every third Opel an engine produced in Vienna.The Viennese facility went into operation 29 years ago. Almost 2,000 workers are engaged at the GM Powertrain Austria factory.Reports have it that the plants staff suggested voluntary cuts of social benefits to help GM in its bid to recover last year. Austrian business press claimed in September the American automotive giant will save 10.6 million Euros because of the works councils decision. Employee representatives reportedly managed to ensure at the same time that GM will not sack any workers engaged in Austria or cut their salaries.Bosses of GM and Austrian-Canadian car industry supplier Magna International signed a pre-contract about a takeover of Opel by Magna International in 2009 before GM surprisingly decided to keep its indebted affiliated firm. Magna was founded by Styrian billionaire Frank Stronach in the 1950s.