NEW YORK--(BUSINESS WIRE)--Fitch Ratings has affirmed one class and upgraded two classes of AmeriCredit Automobile Receivables Trust 2011-4. A full list of rating actions follows at the end of this press release. KEY RATING DRIVERS The rating actions are based on available credit enhancement, loss performance and loss coverage. The collateral pool continues to perform within Fitch's expectations, with low cumulative net losses. Under the credit enhancement structure the securities are able to w