General Motors is paying $3.5 billion in cash to buy subprime auto lender AmeriCredit, a move that will once again give the automaker its own finance arm. General Motors will pay $24.50 a share for AmeriCredit, which represents a 24 percent premium over Wednesday’s closing price.

The Fort Worth, Texas-based finance company typically finances low-mileage, late-model used cars to customers without good credit.

Shares of AmeriCredit shot up 22 percent in pre-market trading Thursday following the announcement.

GM used to have its own finance arm, GMAC, which in addition to making auto loans and providing finance to its dealers was a major subprime mortgage lender. But it sold a majority stake in GMAC in 2006, partly because GM’s junk bond rating from credit agencies made it expensive for the finance firm to raise necessary capital.

GMAC’s problems with both auto finance and subprime mortgages ended up necessitating its own $17 billion bailout from the Treasury. The company, which recently changed its name to Ally Financial, is majority owned by Treasury, making loans to both customers and dealers of both GM and Chrysler Group. But its own need to improve the quality of its loan portfolio has limited its willingness to make subprime auto loans to car buyers of the two companies.

GM said its purchase of AmeriCredit “establishes the core of a new GM captive financing arm that will enable GM to provide customers with a more complete range of financing options.” It pointed to the need to make loans to car buyers with subprime credit scores as well as offering leasing options.

GM itself is still 61 percent owned by Treasury, although it is expected to start selling shares to the public again later this year or early in 2010. Its balance sheet was greatly improved by the bankruptcy process it went through a year ago, leaving it with $23.5 billion in cash and only $5.3 billion of long-term debt.