Re: Ford Taurus 1999 transmission problem
The converter will lock up in 3rd, given the right circumstances, and 4th IS overdrive.
To check lockup, travel over 40 mph on level ground, note the tachometer rpm readings. Tap on the brake pedal enough to light the brake lights, and watch the tach. If the rpms jump ~3-400 rpm for about 5 seconds, and then drop back to what they were prior, your torque converter is locking up. It releases whenever the brake switch is closed.
If the transmission will not shift properly into 2nd gear by itself, but will shift when you move the selector lever to the '2' position, you can make a good guess that the hydraulic parts of the transmission, which make 2nd work, are functional, and you have a control system problem. In other words, the transmission gizzards are ok, but the valve body and or solenoids are malfunctioning.