2000 blazer LT auto 4X4 I have a howl sound only when I LET UP on the gas that is most noticeable at around 45 mph and gets louder the faster I coast especially down hill. I thought that it was the same noise I had when I had to have the r-front bearing replaced so I changed that out with a new bearing and the noise is still there. I have also rotated the tires with no change. Brought the truck to the shop and put it on the lift and the drive train although mostly original is tight. Am I looking at a rear bearing or worse? Any thoughts?