I have a 95 with the 3.4 5 speed manual and when I shift into 3rd it grinds and reverse. What could be the problem?

 

Grinding going into reverse is normal if you do not allow the input shaft time to stop spinning. If you start the car with the clutch pushed in and still grinds going into reverse then you clutch is not fully disengaging. This could be a problem the Master/slave cylinder or the pressure plate.

If reverse is working like it should and 3rd gear is the only gear grinding it is most likely a worn Sync.