One problem related to overdrive light on has been reported for the 1999 Ford Explorer Sport. The most recently reported issues are listed below.
My transmission is slipping especially on the highway o/d light flashes on and off. There are many many complaints on google with people who have had the same problem. Some have had the transmission stick leading to crashes. Ford should have a recall and be make to fix these before they kill someone, if they haven't already. Ford is very aware of this issue, and NHTSA needs to hold them accountable and get our vehicles repaired!!!.