One problem related to transmission not go into gear has been reported for the 1997 Ford Mustang. The most recently reported issues are listed below.
The transmission cannot be shifted into reverse in any reliable manner. Obvious problem since day one. Reported to Ford, they returned with no problem found. Cannot shift into reverse under any emergency condition if such a situation arises. For a period of 2 months, at 18000 miles, had intermittent grinding when upshifting from 1st to 2nd gear when cold. Not reported to Ford since not consistent enough and did not want to bother with no problem found response. Problem has since gone away (for now). Recent incident, had total failure of clutch cable assembly. Could not shift into gear after stopping at traffic light. I was stuck in the middle of the intersection and forced to abandon car in the middle of a very busy road. One individual swerved to miss my car and almost caused a multi car accident. Ford did replace under warranty. They did mention that clutch needs replacement for possible damage to cable failure. No word from Ford if this is under warranty.