2003 Chevy Trailblazer front end vibration

It starts at about 10 mph and continues at the same pitch until I stop. I took off the front wheels and spun the axles. The left side makes a noise, so then I took off the hub. I then spun the shaft and heard a grumbling noiise where the cv shaft goies into the front differential. I was told by someone that it could be the cv bearing, but how do I tell if it is the cv bearing or a diff problem. It makes the noise in 2 wheel drive.The left side is harder to spin when I turn the hub.