Roaring noise sounds like tires but isn't

I've got a 98 Toyota 4-runner. It is making a very loud roaring noise at most all speeds 30 . It gets louder for 30 to 70 and then decreases somewhat above 70. I thought it was the tires. They were only 11 months old so I took it back to the shop and had them replaced (all 4) as a warranty claim. The noise is still there. I can't realy say if it is coming more from the front or back it seems to be all around you. What could be causing this? Differential, Bearings, What? Hi peekster:

A few things could be causing your problem:

1) a bad wheel bearing.

2) you transfer case is getting noisy, due to wear.

3) you Rear-end gears could be developing excessive clearence Car Repair Talk's forum.