One problem related to steering knuckle spindle has been reported for the 1999 Ford Explorer. The most recently reported issues are listed below.
Dealer states " out of warranty" , vehicle allmost rolled over due to complets separation of the front wheel and spindle from vehicle. This will most likely be a defective assembly or poor engineering. Bolt for upper spindle to ball joint broken or missing and ball joint shaft sheared off. Brake line broken off and axle seperated from the housing. Recommend a recall on this very poor design and or a replacement of all these ball joints produced by whatever company made this ball joint.