Sounds like it could be the drive axle but it could be many things. I would leave it with the dealer and ask them to fix it. I have had several vehicles mostly my kids beasts that they trashed and the drive axle will make a steady noise as it falls slowley apart. I should not say falls apart FAILS. But if thats it the drive axle it could fall apart if left unchecked. The last one I had the extrem pleasure of dealing with was my sons Mercury Sable and the support bearing in the swing arm went. It fell apart and actually the axle pulled out of the tranny case. Drive it till it drops is his motto. Click and Clack love guys like him