While coming home from work I had the most disturbing vibration-rattling come through the shifter. I was cruising up to the driveway and, only going about 10-15MPH, clutch fully depressed, had it in first gear, revved it up to about 3500 or so. At the peak RPM the vibration-rattling coming up through the shift made if feel like I was holding a nail gun set on auto fire. The car drives fine, I don't beat on it (yes, honestly), and I had the clutch assembly replaced, flywheel machined, less than 6 months ago. Any ideas?