One problem related to transmission solenoid has been reported for the 1998 Ford Explorer. The most recently reported issues are listed below.
Transmission slips when shifting into gear and clunks. Transmission disengaging out of drive gear; will not stay in gear when moving in the forward (drive) direction. Almost was in wreck due to transmission/drive failure. Had taken vehicle in to transmission specialty service station to have looked at. Faulty solenoid and stuck mechanism due to failure. Total cost of repair $1700. 00.