Nissan Xterra Noise

03 Xterra makes whinning noise at 2200-2500 rpm. Noise goes away outside this range. At 3000 rpm sounds like tachy cable rattles. Have had Nissan check trans, diff, muffler. No luck. Help!!

Could be an accessory (water pump, alternator etc.) bearing.
Use a piece of hose as a stethoscope.