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.
To find out if the vibration is from the torque converter lock-up clutch, when the vibration starts, lightly step on the brake pedal while maintaining speed.
This will disengage the clutch.
If the vibration stops, it’s the clutch. If the vibration doesn’t stop, it’s not the clutch.
It vibrates in overdrive, and also not in overdrive? So it vibrates most of the time then. hmm … well, vibrations can come from other things than the transmission. If the advice above doesn’t pan out, first thing, do some experiments (coasting, swapping the wheels around, etc) to see what exactly the vibration tracks. Vehicle speed? Engine rpm? Brake involvement. Tires.
If your shop is pretty certain it is the transmission that’s causing it (based on a test drive presumably), the idea to add something to the transmission fluid to soften the seals might work temporarily at least. Auto-transmission shift logic is based on fluid pressures in the valve body, and if the seals there leak the fluid pressures leak down too, then the transmission gets confused and this symptom can result. It’s like if the wires inside your computer started to short out, who knows what would happen. But it wouldn’t be good.
Keeping the transmission fluid fresh and clean is the best insurance against the seals hardening.