Have an 08 Dodge Nitro SXT 4x4, AUTO, 3.7L V6. 42000 miles. The car has had its share of problems that have cost plenty to repair. The latest issue; Driving at speeds 30 to 35 mph, the transmission begins vibrating continuous until I reach speeds over 35 to 40mph. It is also noticeable at speeds just over 50 to 60 mph. I recently had the transmission flushed, refilled with new fluids and had the new filter installed. Still a Problem! PLEASE HELP!