rubbing sound from under vehicle while driving

2002 mercury mountaineer AWD, 152000 miles, hear and feel what sounds like tires rubbing at random speeds, going straight, no acceleration, no braking. The rear brakes and rotors do need replaced per dealer, which is causing rear brake noise, but today I felt what appears to be random rubbing noises from under the vehicle. Examined all 4 wheel wells and did not see any visible signs of rubbing on the tires, except maybe for the right front. There is about an inch of clearance on the inside top front tire and part of the suspension. I assume that is normal, since it's on both sides. But the rubbing noise sounds like it's under and behind the vehicle. The rear axle needs to be topped off per the dealer, but hasn't in a while. Any ideas before we take it to a repair shop? Thanks!

Welcome to the forum!

Does the rubbing noise seem to change with vehicle speed or seem constant, regardless of speed? Does the noise go away immediately if you accelerated or lightly step on the brake pedal?

-Rod

the noise happens regardless if I am accelerating or coasting...braking has no effect. Occurs mostly at 50mph, but have heard/felt the "rubbing" at speeds lower then 50. It comes and goes at random. The SUV is at the dealer and they diagnosed it as the rear differential, which needs rebuilt. $1300 Dealer said they listened to clatter via a stethescope (sp) The truck runs smooth except for the random rubbing/vibration noise at random speeds

Sorry, to answer your question about rubbing noise change - it does not change...seems to come and go at the same "rate" Speed has no effect on the sound. thanks for the quick reply!