Hi - I have a 2004 MonteCarlo with 143,000 miles making a loud sound like a bad muffler - took it in and had the muffler replaced (it was bad) but the sound didn't go away. The sound starts at about 20mph and gets louder as I go faster and disappears when I steer/turn right. Took it back to mechanic who replaced both front hub bearings (both were bad he said) but now I still have the sound - no different. He rotated the tires - no change - had tires checked - no problem. Mechanic didn't think it was rear bearings - said that was rare. Any suggestions? I can't tell where the sound is coming from - just under the car somewhere. Thanks - Betsi

 

Did the mechanic check the constant velocity joints? My experience with front wheel drive cars is when you have a noise such as you are describing and the noise stops when turning then the CV joint is bad. when you turn right and the noise stops the CV joint on the right is bad, if the left joint was bad then when you turned left the noise would stop.

Look under the vehicle and inspect the rubber boots around the CV joint for tears, deterioration, leakage etc..

Here is a CV shaft with a bad boot