NEW YORK (CNNMoney.com) - General Motors Corp. Tuesday restated nearly four years of results for its GMAC finance unit -- a subsidiary it's trying to sell a controlling stake in to raise cash and give a boost to its finances.

The restatement was disclosed in filings with regulators, including its 10-K report for 2005, which details full-year results.

GM's statement warns that the accounting change could affect its ability "to complete a transaction with a strategic investor regarding a controlling interest in GMAC while maintaining a significant stake in GMAC." But that warning came in a long list of possible risks that are generally boiler plate in such financial disclosures.

Realistically, analysts believe that the sale will not be derailed by the accounting disclosures, though the questions certainly don't make GM's negotiations any easier.

"I would have to believe at this point that bidders who are serious players, to the extent they've already done their due diligence, this is not a surprise," said auto analyst Kevin Tynan of Argus Research earlier this month when the GMAC accounting issues were first disclosed. "What it could do is tip the balance more to the buyer, give them a little more leverage on the price."

The good news for GM (Research) was that it made the 10-K filing after missing an earlier deadline with the SEC. But the restatement was another sign of turmoil at the troubled automaker. The already battered shares of the Dow component were down another 1.3 percent in after-hours trading Tuesday following the latest announcement.

In a statement Tuesday, GM said the restatement affected GMAC's cash flow but not its earnings or its balance sheets for the periods reported. Cash flow is earnings plus depreciation and other non-cash charges such as amortization.

On March 15, the day GM missed the original 10-K deadline, the company first disclosed it has encountered some accounting questions involving GMAC. At the time, the company raised its loss estimate for 2005 by $ 2 billion to give it a net loss of $10.6 billion.

"In concluding the review, GM determined that the cash flows related to certain mortgage activities were not appropriately classified as either operating cash flows or investing cash flows," said a statement from GM Tuesday. "These changes reduced operating cash flows and increased investing cash flows in each respective period by the same amount.

The finance unit is by far the most profitable operation at General Motors, producing net income of $2.8 billion in 2005, while GM as a whole reported a loss, Reuters reported.

GMAC's mortgage business became its primary profit driver last year, producing $1.4 billion in earnings compared with $1.1 billion from auto finance, the news agency said.

Still, GMAC's operations have been hampered since GM's debt got cut to "junk bond" status by the major debt-rating agencies, a move that raised GM's cost of raising capital.

A sale of a majority stake in GMAC is seen as the surest way to restore its investment grade rating, while at the same time providing a cash infusion for GM's embattled auto operations.

For more on GM's accounting headaches, click here.