One problem related to front suspension upper ball joint has been reported for the 1999 Ford Explorer. The most recently reported issues are listed below.
I own a 1999 Explorer with 60000 miles on it. I have been told that the front upper ball joints were bad, and had to be replaced with the control arm since it was one unit. Why were sealed ball joints that were part of the control arm being used, unless it was to raise the frequency and cost of repairs at the expense of public safety . A ball joint failure at any speed could potentially have grave consequences. Consumer had vehicles routinely go well over 100,000 miles with non sealed ball joints, and had no problems. This warrants further investigation, especially since consumer became aware that his problem is by no means an isolated case. Had been told that the local dealer was doing a lot of those, and that they were aware there was a problem with them.