DETROIT (Reuters) - Southeastern Asset Management, a Memphis-based value investment firm, has sold a 7.9-percent stake in General Motors Corp (GM.N: Quote, , Research, ) and swapped into a large position in the automaker's senior convertible debt, according to filings with securities regulators. The move by Southeastern, one of GM's largest investors, came after GM announced earlier this quarter that it was suspending its common stock dividend as part of a plan to shore up cash and survive a deep slump in the U.S. auto market. A representative of Southeastern, which is headed by O. Mason Hawkins, was not immediately available to comment. The shift in the firm's GM holdings was detailed in a pair of filings with the U.S. Securities and Exchange Commission on Wednesday. As of the end of June, Southeastern, which manages the Longleaf Partners Fund and other discretionary accounts, held almost 45 million shares of GM common stock, equal to a 7.9 percent stake in the automaker. In Wednesday's filing, Southeastern said it held 34 million shares of GM's Series B Senior Convertible Debt. That holding can be converted into a 2.3-percent stake in GM's common stock, the firm said. The filings did not say when Southeastern sold its common stock in GM or when it had bought the convertible debt. GM shares rallied by almost 12 percent on Thursday on low oil prices and rising hopes that funding for $25 billion in federal loan guarantees to the auto industry could be cleared by lawmakers and ease some of the pressure on GM's liquidity. Despite the rally, GM shares remain down about 50 percent this year and over 80 percent since Chief Executive Rick Wagoner took over in 2000.