Hi, I have a 2008 SLT 4WD with 182,000 miles. While driving in 2WD, I have a hum and vibration coming from the front end, which is timed to the wheel rotation and not the engine revs. It started intermittently approx 1 year ago. Now, it is continuous. I can feel it mainly through the accel pedal. I can start to hear/feel it at approx 40-45 mph and it gets louder/more noticeable as I increase speed - at 75 mph, it is loud and I can feel it through the steering wheel. When in 4WD, it goes away unless coasting down a hill. I think it might be the axles or transfer case. I changed both front hubs around 20K miles ago. My tires are relatively new and are balanced. I changed brake pads and rotors approx 5K miles ago. Any ideas?