Reducing Transmission Gear Noise or Whine

I didn't have any problem with transmission gear noise coming into the cockpit until I installed the aftermarket carbon-fiber shift knob shown above.   It attached to the shift lever with set screws, provided good path for vibration to travel up the tri-ax shifter, and I began to hear a buzzz in third gear.   When I removed this shift knob and reinstalled the factory knob with its rubber/plastic screw mount, the noise went away. As an additional precaution against vibration and noise becomeing a problem again, I also tried a tip I read about elsewhere -- putting a rubber coating on the billet aluminum shift handle to prevent it from vibrating.   Don't know how much that helped, but once again I have no noise coming from my tri-ax shifter.