Just out of curiousity, did you check the back suspension and wheel bearings? Sometimes when you hear a noise when we think it is coming from the front, believe it or not problems can arise with rear wheel bearings, or suspension when we hear a noise and we have the windows up. Most cases it will sound as if it is coming from the front.
Roll the window down and stick your head out and turn the wheel and listen, 9 out ot 10 times you will hear the noise coming form the back. When a car is in motion and you turn the steering wheel, it actually makes the rear suspension move in unison, due to weight distribution on the rear of the vehicle, even if it is only moving 3 miles an hour, so it IS possible that it is coming from the rear.
To make less work for you, lift the rear of the vehicle and check the rear wheel bearings by seeing if the rear tires have any play in them by moving them in and out, up and down, and side to side, then still if no play in the rear wheels, remove the tire and remove the rear wheel bearings and clean them and take a look at them after they are clean. If the bearings or race shows pitting or wear, then that is where your humming is coming from, could also be the popping noise if the wheel bearing has any play in them. But once you check the wheel bearings, do the following just to be sure.
Lift the rear of the vehicle and try and support the body on jack stands with the suspension totally off the ground, (you may have to actually go to a place that has a car lift to do this, as the jack stands may not get the suspension totally off the ground) Once you have the suspension off the ground, (make sure that the car is stable so it won't fall down on you) shake the crap out of the rear suspension forward and backward, up and down on each side. Check your shocks, spring coils to see if they show signs of movement around the spring mounts, or springs for breakage, Also, check the suspension brackets from the rear axle to the car body and make sure they are not bent and the bushings look good and not dry rotted and torn.
Hope this works for you.
Last edited by TheHarleyMan2; 02-19-2006 at 07:51 AM.