I have a Ford Taurus 2004 SES, Duratec 24v, with 80,000 miles. Transmission fluid never changed yet. Lovely car to drive. Started to show a vibration at 1600 RM in overdrive. The fluid looks full and ok (pinkish). Took to the mechanic, he said that Taurus has been troublesome with transmission and suggested me to change (not flush) the fluid + filter ($150). He said that the problem is with overdrive and it is starting to show, but will not show immediately. He said he would use a special additive and makes residues soft and have them off. He did not guarantee that this would solve the problem. He also said that it would not vibrate if it is not in overdrive. However, I drove it in regular drive and it made the same vibration.
I thought to check with my friends here first. Please advise if you think this is the right approach or something else I should try first.