Another humming noise question


I have a 2002 Chevy Suburban with 123,000 miles . At about 67mph and up to 70mph it makes a humming noise from the rear and is louder the faster I go .I have not been over 70 so I do not know if it continues. I jacked up the truck and checked all tires for looseness by putting my hands at 9 and 3 and there is no in and out movement nor no grinding noise when spinning the tire . There is no grinding noise either when making a left or right hand turn. There is no other noise at slower speeds to think it might be in the drive train. The tires have about 1200 miles on them so I was wondering if it might be them .

Also both front tires have a small amount of play in them. When the front was jacked up both tires moved in and out (as if turning) about a 1/2 inch at the same time. I was wondering if this is common with a GM product to have a looose front end as I have read some articles about this being a weakness of a GM product or if it might be balljoints. There is no play in the steering wheel as the tires turn when I move the wheel so this rules out the idler and pitmen arm I believe.

I know the humming noise has been brought up many times I cant image that the tires ( Cooper brand ) being so new could cause the humming noise but anything is possible.

Any imput would be helpfull . Thanks