My truck developed the vibration and it would shutter while shifting so I took it in to my dealer for the oil change and went over it with them a few weeks ago. They tested the torque converter slippage and said that was my problem. They replaced it just before a big trip from FL to MI and just over 3000 miles. It's like driving a completely new truck. There is Zero vibration and the little bit of clunking (usually only when shifting into drive from park) I had is gone.
On another note. I got 21.1 mpg over all which included driving 75-77 on the interstate, letting my bro-in-law pull his boat some in NC and around the towns in our destinations.