2005 chevy tahoe has a terrible roar coming from the rear differential. The roar becomes an unbearable whine at 45 mph. Any ideas what is causing this problem?

4x4? Check driveshaft and differentials

If the sensor is not in the transmission, it could be in the rear differential. The sensors at the wheels and differentials are usually for the abs system.

Yes, Rebuild the differential BEFORE it leaves you on the side of the road!!!!!

Bad wheel bearing most likely.

Differential roaring noise is usually caused by a bearing that is worn or has pitting in the bearing race (half of bearing without rollers). A whining noise would be caused by worn ring and pinion gears. the roaring could be from the carrier bearings (two bearings holding the differential case to the axle housing) or fron the pinion bearings. The fluid is typically heavier but will seem thin when hot. The fluid isn't the causing of the noise but if the wrong fluid is in the differntial it could have caused the bearing to go bad which then causes the noise. good luck.

possibly a rear axle bearing. they do make a roaring and whining sound when driving.

try the cooling fan its controlled by a thermo clutch,check it out.go online they tell you how.or if the fan free wheels to easy it likely is defective.

need to check wheel bearings

could be power steering pump low on fluid

i'm thinking that your tires need speed balancing :),, if is not the tires then one of your bearings on the hub needs replacing or the exhaust has a hole somewhere.