Venture Whirring Problems
 

When driving my Venture (2002 WB), when the wheels begin to move, a whirring noise is then heard. It seems to get faster and louder as speed increases. It ends when stopped. When I coast, the noise is still there. I had it in a shop today and he doesn't really know. It's definitely not the wheel bearings. However, he thinks it may be the pinion bearing. Any ideas and costs???