The Police Interceptor I purchased, with about 100,000 miles, has transmission issues. The vehicle has difficulty going to Reverse. This is intensified when the temperature goes up. Transmission fluid looks fine but I don't think it was ever changed.
When you say difficult do you mean shifting the gears? Check the shift column for worn out bushings. On the bottom of the shift tube under the dash, it would come loose and shifting gears may not put the gear all the way in, causing the transmission to shift poorly.
Have a mechanic, like one from YourMechanic, inspect your shifting difficulty issue, and recommend the best path to repair.
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