NEW YORK — Troubled auto and home lender GMAC Financial Services said Monday CEO Alvaro de Molina is stepping down.

Michael A. Carpenter, a member of the company's board of directors, has been named his successor.

De Molina's sudden resignation comes while the lender is in the midst of negotiating with the Treasury Department over additional taxpayer assistance. GMAC is instrumental to the operations of automakers General Motors Co. and Chrysler Group LLC, but its finances have been haunted by bad loans it made during the housing boom.

GMAC, based in Detroit, said it has asked the federal government to postpone any decision on additional taxpayer aid until Carpenter and the company's management assess the company's situation and can advise Treasury on the amount needed and what form it might take.

De Molina said in a statement it was a "good time for me to move on to my next chapter," though he did not say his next move.

"I came to GMAC thinking that it was a short-term assignment working through a liquidity crisis. That crisis lasted two years," he said.

Carpenter, 62, has been on GMAC's board since May and has held CEO positions at a unit of Citigroup as well as at other financial and insurance firms. GMAC said he has resigned from the board of CIT Group to devote his full attention to GMAC.