i have an 04 f-150 supercrew 4x4 lariat with 103k miles that has a pretty bad vibration between 45-50 after it switches into overdrive, when you turn overdrive off the problem goes away. ive taken it to the dealer and they put shutter guard in it an said to let it work through for a couple hundred miles. it still hasnt gotten any better, does anybody have any idea what it is?