Started noticing a month ago...and surprisingly it has not gone away. Symptoms: Part 1: First thing I noticed was when I took her out after washing to clear stubborn water off, I noticed a relatively soft "clunk" when shifting (casual shifting, not accelerating too hard). It didn't do it all the time, and if I was more ginger with my clutch engagement, it didn't do it. But, casual acceleration with casual gear changes would result in a noticeable (sound and feel) clunk. Part 2: The next thing I became aware of was an occasional vibration at speeds over 75. This vibration is not constant, but more cyclical when I feel it. I would feel a vibration for 4-5 seconds then it would disappear for 2-3 seconds, and then return....and this would just repeat. Upon experimenting (ie. coasting with the clutch in, coasting with the clutch out), I have determined that the vibration is coming from the driveshaft. Coasting, engaging the clutch or not, does not eliminate the vibration. I am suspecting either U-joints or carrier bearing. Aside from CAI and tune, the car is pretty much stock (2011 GT with 80k miles). Anyone have experience with this?