Delinquencies on auto loans plunged in the first quarter, falling 17.8% nationwide, according to the latest analysis by TransUnion LLC. The share of auto loans on which payments were at least 60 days overdue fell to 0.65% in the first quarter from 0.79% in the final quarter of 2007, the credit information company found. "Historically, there is a decrease in 60-day auto loan delinquencies between the fourth and first quarters," TransUnion officials said. "However, the [nearly] 18% drop is the sharpest in four years."