GM customers will now have a wider selection of financing options, potentially making sales for the struggling American giant more viable.
GMAC gave up its rights under conditions set by the US government for the bailout of the lender.
GMAC agreed to give the government 5 million of its preferred shares in exchange for a capital injection of $5bn (£3.4bn) to help the lender avoid bankruptcy.
Last week’s deal also said GMAC no longer had to provide lease financing.
GM sales in the form of leases have declined drastically in recent months due to weak used car values and low demand for this type of debt from secondary credit markets.