One problem related to transmission stuck in gear has been reported for the 1998 Mercury Sable. The most recently reported issues are listed below.
I've noticed since purchasing the vehicle, that it sometimes hesitates when you step on the gas from a dead start and you must maintain your foot on the pedal until it shifts or it would jerk. I've never driven a vehicle that performed this way and not knowing much about cars, didn't know there was a problem. Now it's stuck in gear at 60mph. It has also droped into neutral for no apparent reason but once I shifted it into reverse and then drive, the gear kicked in.