Ally Financial's (GJM) GMAC Mortgage holds the highest serious delinquency rate of Ginnie Mae-backed mortgages for any servicer, according to a report from investment bank Credit Suisse. Ginnie guarantees investors the timely payment of principal and interest on mortgage-backed securities containing federally insured loans, mainly through the Federal Housing Administration. The 2007 vintage of Ginnie-backed mortgages holds more delinquent loans by percentage than any other, and across all coupon stacks, the 6% segment is the most troubled. According to Credit Suisse analysis, of the Ginnie mortgages that fall into those two categories, 17.6% are in 90-plus delinquency or worse. The next highest is servicer is Taylor, Bean & Whitaker at a 7.1% serious delinquency rate. For Bank of America (BAC), the rate is at 4.1%. Each servicer below that, including JPMorgan Chase (JPM), Citigroup (C) and Wells Fargo (WFC) had serious delinquency rates of that vintage and coupon stack below 2%. Earlier in the week, Ginnie said it would begin disclosing which loans in its pools had been through the loss mitigation process. These loans would qualify for that disclosure, but Credit Suisse analysts said modified loans reset their duration expectancy, or the expected amount of time it would either default or pre-pay. In comparison, mortgages that were brought current under the same terms are easier to identify because the duration expectancy doesn't reset. Write to Jon Prior.