I just bought a 2000 Z28, and when I bought it it had a noticeable but not overly loud hum from the rear. It has escalated pretty quickly to almost a loud scrape or grinding all the time. I had thought the rear brakes were torn down (my friend had worn the entire pad off his brakes on his stealth, and it made a similar noise). But upon inspection of hte brakes, I find there was still a good half of the life on the pads. What else could it be, and how would I check to elminate some things? thanks!

 

Check the rear end fluid

 

Lift the rear end off the ground, so that the tires are off the ground and have someone rotate one tire one way af fast as they can and listen for that grinding if u hear it its the rear