Toyota Motor Corp. retained the No. 1 spot by a slim margin after sustaining the biggest year-over-year drop in score in the study's eight-year history. Honda Motor Co. came in second, while Nissan Motor Co.'s ratings fell sharply.

'In the years we've been conducting this study, we've never seen such dramatic year-over-year shifts in the rankings,' said John Henke, president and CEO of Planning Perspectives.

'Chrysler's showing is especially unfortunate,' he said. The carmaker was highly regarded by suppliers in the 1990s 'but today has fallen rather dramatically since being taken over by Cerberus' Capital Management LP.

A Chrysler spokesman said the automaker was working hard to improve relationships with its suppliers and had established a supplier relations team this year.

'We want to try to rebuild the trust in the relationships,' said spokesman Kevin Frazier.

Ford officials were pleased with the results. It was the only automaker whose scores improved.

'We've been at this since the end of 2005,' said Tony Brown, Ford's global purchasing chief.

Three years ago, Ford embarked on a strategy to cut the number of suppliers but build better relationships with them.

'We're trying to position our supply base and ourselves for profitable growth,' Brown said. 'We've still got a lot of work to do.'

General Motors Corp.'s ratings slipped but have improved over prior years. 'The study gives us important feedback that we can use to continue to improve our relationship with our supply base,' GM spokeswoman Deborah Silverman said.