One problem related to clunking noise has been reported for the 1999 Ford Windstar. The most recently reported issues are listed below.
1999 Ford Windstar - broken rear axle - van made minor clunking noises at low speed over bumps. On the highway, the van acted like the rear end was loose / tracking badly. A flashlight inspection at home showed a large open-gaped crack in the rear axle. Negative camber noticeable on driver-side rear tire. There are numerous examples on internet car forums with photographs documenting identical axle failures. Some reports mentioned total failures that led to motor vehicle accidents. The van is presently at a Ford dealer pending repair. Dealer personnel had no knowledge of this issue. I am extremely concerned for Windstar owners that may not be aware of the problem. Windstars are often used as school vehicles. I hope present Windstar owners can be notified prior to any fatality occurring.