The National Highway Traffic Safety Administration opened a preliminary investigation of the problem on May 13 after receiving 234 reports of rear axle fractures and two minor crashes. The number of complaints has risen to 950.
NHTSA said the design of the axle appears to allow it to collect road salt slush, leading to rust.
The recalls total about 463,000 in the United States, and the remaining in Canada, a Ford spokesman said.
Windstar owners will be asked to bring their vans into Ford or Lincoln-Mercury dealerships for inspection of the axle.
If the axle shows a crack, owners will be offered a repair or alternative transportation until parts are available, Ford told NHTSA.
If there is no cracking, owners will be informed when to return to have reinforcing brackets placed on the axle, Ford told NHTSA.
The recall affects vans in Canada and Connecticut, Delaware, the District of Columbia, Illinois, Indiana, Iowa, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Vermont, West Virginia and Wisconsin. (Reporting by Bernie Woodall; editing by John Wallace and Matthew Lewis)