Toyota Repair: 4runner noise, pinion bearings, axle bearings

Question
My 1999 2wd 4runner (125,000 miles) recently started making a rumbling noise at speeds only between 60-70 mph.  I recently had the u joints on the driveline replaced which solved a vibration problem, but not the rumbling noise.  I also had the tires balanced and rotated, but the problem still persists.  The tires are 2yrs old and I did not have the problem when I first purchased them, so I don't think it's tire related.  Is the problem coming from the differental?

Answer
Possibly one of the rear axle bearings or the differential pinion bearings, this can be checked with the truck up on a rack and the engine running and in gear, someone should be inside to bring the speed up to about 30-40mph, the noise can be pinpointed by using a rubber hose to the ear and touching it to these areas.