1997 Chevrolet Suburban High pitch grinding sound + whistleing

When driving the suburban you can feel its tension in the floor board, and when driving down the road she sounds like she is choking on top of the high pitch grinding noise and whistle until you get up to approx 70/75mph. If you hold her at 70/75, she goes quiet. She started spitting what looked and smelled like grease from around the two front tires. We disabled the 4wd on her thinking that was the issue, but once we got her back from the mechanic the noises were still there. Now something in the rear popped and we are unsure to as of what.