The Ford Automatic Transmission have been plagued with problems way back to the 4 speed version of the 5 speed and 6 speed used on the Sport Trac's (as well as other Ford vehicles)
Because of Ford's history of transmission problems, I flushed my transmission within 30K miles on both my 2001 and 2003 Sport Trac's. I never noticed any problems with the 2001, but after getting the transmission flushed and refilled with a 100% synthetic Mercon-V, it was like a new truck. Shifts were firm and quick and even acceleration was much quicker. I never felt any problems with my 2003, but I had the same flush done at only 20K miles as a precautionary measure. I did not notice any difference in the shifting or performance, but that was OK since it only cost $85 and that was cheap insurance. I traded in the 2003 with 34K miles and never had any problems.
As Todd said, it depends on how your drive and how long you keep your vehicles. If you replace them every couple of years, then you probably don't want to spend a lot of money on maintenance that may only benefit the next owner, but then it might just jump up and bite you in the ass while you still own the truck? It's the old "Pay me now or pay me later"
You do not have to get your fluid or cooling system flushed at the Ford Dealer...They will likely charge you about twice what an independent shop would charge.
...Rich
