I have a 96 Ford Winstar with 140,000 miles. I have noticed that when I come to a stop, the transmission down shifts into first gear with a lunge. I understand that this vehicle has a history of torque converter problems. What are the symptoms of a defective torque converter.

torque converter problems you will have leakage and/or slippage. Your problem sounds like the 1-2 sensor is bad.tranny is computer operated and the check engine light will not come on, called a soft code. tranny has two sensors, 1-2 and the 3-4 sensor. change it, it easy,it has its own unique plug in so you'll know which one it is when you buy the new one.