A GMAC auto loan is a consumer debt instrument that is issued to help finance the purchase of an automobile. Wikipedia explains that In 2010, GMAC changed its name to Ally Financial, but it continued to offer vehicle financing to qualified customers.
GMAC auto loans are issued exclusively through authorized dealers, usually at the time of purchase, as a way of expediting the car-buying process. According to the company website, GMAC financing is available to cover up to 80 percent of private vehicle prices and 70 percent of the purchase price of commercial vehicles. GMAC loans have repayment terms of between 13 and 60 months.