RepairPal Certified shops can diagnose and repair your 2001 Mercury Sable. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
You have not said whether you checked fluid level or not. If low on fluid the trans cannot work properly. Give us more info. If fluid is full then may need to go to trans shop. Do not overfill trans fluid or use incorrect fluid.