1999 Audi A4 front end vibration

1999 Audi A4 All Wheel Drive Automatic 160000 miles

There is a slight vibration and low pitched sound that seems to coincide with the rotation of the front right wheel. It is not noticeable at high speed, but mostly when the car is warmed up, slowing down and turning left. Following our mechanics suggestions, we have replaced the rotors and pads, and also the front right wheel bearing. The noise and vibration are still there. He says it could be coming from the drive train, but now we are not sure what to do. Help