Ford explorer 2003
 

Growling in front end. Put two new tires on. Growling still there. Has to be wheel bearings. Drove the car today and noticed a pulsating. Even when shifted into neutral the pulsating was there. Anyone have any ideas? The pulsation is there when the car is coasting also. Not touching the brakes, so I know it's not that. It feels like something to do with the auto 4x4 system. Could there be a sensor going bad?
Thanks, Jake