I've got one of these too. Changed front drive line, no difference. Rebuilt front diff, no change, Changed wheels and tires, no difference. I am running out of options. Van has never been wrecked. It is a high freq. vib. that sets up a hum in the floor, in front. Not front wheel bearing either, I changed them one at the time. I've driven it 16,000 miles with no change in the noise. I'm desperate and wishing a tree would fall on it.