I have a 4.2L trailblazer with 160,000 miles. When I get to 35mph and go faster I hear a sound that sounds like a semi. It's coming from in front of me if I was driving. I replaced the tensioner and pulley and a idler pulley. The belt looks good. I don't notice the noise when I rev it up in neutral or when I raised it up in the air which was like Ferris Beuller day off and prob not safe. Any ideas?

 

if its a growling noise inspect the tires for irregular treadwear. if the noise changes when you sway the vehicle left or right, it could be a wheel bearing.

 

The sound doesn't change when stearing left to right but I'll check the wear.

 

i would suspect a wheel bearing also. jack up the front and wiggle both front tires (up-down) compare the two sides