I have a 2001 Grand Marquis with 57,000 miles on it. Between 40-55 mph the car will start shifting back and forth. It feels like the engine is missing, but it only does it at these speeds, an it stops if you turn the overdrive off by pushing the button on the end of the gear selector. It does it whether the engine & transmission is hot or cold and the engine light does not come on.


Does this mean the transmission is going out? Will this process of constant shifting cause the transmission to prematurely wear out? Does anyone know what is wrong with thus car?