Sport trac od transmission light blinks?

As the manual says that if this light starts to flash on and off or stays on for a period of time that you must have your vehicle serviced immediately. This o/d light is referring to the transmission. O/d stands for overdrive. The transmission uses overdrive to provide more power to the wheels when the vehicle is rapidly accelerating or climbing a hill. After a certain point it will shift into the next higher gear and the revs should go down. The light flashing is indicating that there is either a loose connection or that your tranny is slipping. This is very critical to have serviced immediately. Transmissions are costly and especially with this model I have heard alot of them having to be completely replaced. The earlier you catch it the better. Take your vehicle to a transmission specialist and have them quote you on the problem ASAP.