The Contours had poor quality automatic transmissions from the factory. Your overdrive has simply worn out. The best course of action would actually be to have the transmission rebuilt. It will cost you little more than just having the overdrive fixed and will save you from repairs too soon in the future. Until you have the transmission fixed, simply turn overdrive off (or drive in 3rd gear), even on the highway. you may lose some gas mileage, but the car can be driven that way. After you have the transmission repaired, don't use overdrive at lower speeds (under 45 mph) and around town. It will greatly increase the life of your newly repaired transmission.
