Check your tire pressures and make sure it has the pressure stated on the door. Have the rear end checked to see if it has gear oil in it. Check for leaks on the rims, around the axles. Don't drive it any further than you absolutely have to. It could be road noice for the type of pavement finish/tires, etc. It would be very odd for the car to shed the rear end for no reason. Some 2005s still have power train warranty left depending on when they were purchased,etc. Check that too.