My car has recently developed a strange vibration when accelerating. It is most noticeable when in 1st and 2nd gear, going WOT. It starts at about 5K RPM and becomes much more pronounced as the revs climb. The vibration is high frequency in nature, and it really shakes the car near redline.

I've also noticed a rattling sound coming from the back of the car. It is back towards the diff. Coincidence?