How does one tell when these modern front wheel drive wheel bearing/hub units are worn? We have a 2003 Chevy Impala with 125k miles and it has developed a humming noise from the front end; my wife thinks there is a vibration in the steering wheel as well.
One way to test for a worn bearing is to raise the wheel in question, grab the tire at the 12:00 and 6:00 oclock positions. Now try rocking the top and bottom of the tire in and out. There should be no slop. If there is, that bearing is probably worn.
Or grab the strut spring, and slowly rotate the tire. A bad bearing will sometimes transmit its roughness into the spring where it can be felt.