I recently bought a used 2013 Lincoln mkz with the 3 liter v6 and awd. I noticed a humming noise and slight vibration coming from underneath the drivers side, it is most noticeable when driving between 50 and 65 miles per hour. The hum and accompanying vibration is low and rhythmic and increases in frequency when turning left, decreases when turning right. Anybody else experience this, know what might be causing it or know of this is just a normal sound for the car? Thanks for any help.