The guy who had a bad vibration even after four wheel balancing and new tires will not be helped by a new drive axle. He may have wheels with holes slightly larger than the wheel studs so that when installed, the wheels are slightly off center. Even perfectly balanced wheels and tires will bounce if not exactly centered on the drive flange. May be able to detect this by raising the car and slowly rotating the wheel with a dial test indicator against the edge of the rim.