Ed,
Your profile indicates your Sport Trac is a 2002 model. Is this a used vehicle that you recently purchased, or am I to assume that you have never changed your transmission fluid? If you have changed your ATF regularly, what fluid did you use in the past? Not all brands of Mercon-V are or were full synthetics.
If you have never changed the ATF, or it has been a long time since it was changed, you are probably better off having the transmission flushed, the filter changed and the fluid replaced with a quality brand name Fully Synthetic Mercon-V.
As I understand, early model Sport Tracs came from the factory with a Semi-Synthetic version of Mercon-V ATF. Since then Ford has changed to a Fully Synthetic Mercon-V...probably because of all the transmission problems owners had with the early Sport Tracs
Also, there was a recall issue for some 2002-2003 Sport Tracs for dealers to add bottle of a Friction Modifier to the transmission fluid...but only if the transmissions displayed specific symptoms? They claimed that the supplier provided the wrong ATF fluid to the Louisville Assembly Plant.
...Rich