I have been having the same problem the last few weeks. The mechanic I took it to said I had a bad drivers side cv shaft and wheel bearing. He admitted he had problems putting the new shaft in and it has not fixed the problem. My husband looked at it and saw the drivers side ball joint had a busted seal and was leaking grease so we fixed that. Still have the same vibration problem. I took it the tire and alignment shop today and they said to rotate and balance the tires which didn't help either. They did say my tires were cupped and would contribute to a vibration, but the vibration between 40 and 60 is horrid. I'm lost as to what to do next!