A Lehman Brothers Holdings Inc. unit sued AmeriCredit Financial Services Inc. for breach of contract, alleging it undervalued termination payments for interest rate swap agreements connected to auto-loan securitizations.

Lehman Brothers Special Financing Inc. entered into swap agreements with trusts sponsored in 2005 and 2007 by AmeriCredit that issued $3.85 billion in notes, according to a complaint filed today in federal bankruptcy court in Manhattan, reported Bloomberg. AmeriCredit Financial, a subprime auto lender based in Fort Worth, Texas, was bought by General Motors Co. last year.

When Lehman filed for bankruptcy protection, the swaps were terminated and AmeriCredit failed to calculate termination payments according to the terms of the agreement by not seeking bids from potential replacement counterparties when interest rates were moving in Lehman’s favor, according to the complaint.

While AmeriCredit made early termination payments of $13 million, Lehman should have received $42.5 million, according to the complaint. The lawsuit seeks $13 million in interest from three swap agreements and other unspecified damages.

Caitlin DeYoung, a spokeswoman for General Motors Financial, didn’t immediately return a voice-mail message left after regular business hours.

The case is Lehman Brothers Special Financing v. AmeriCredit Financial Services, 11-2403, U.S. Bankruptcy Court, Southern District of New York (Manhattan).