Gear oil did not stop roaring noise for 2008 xc90 volve

Possible wheel bearing that is worn. Have the bearings inspected.

It sounds like it could be in the rear diff not the bearings normally they make a roaring noise. Have you tried cleaning and adjusting the rear brakes. I would try that and see if it helps

if it is a rear wheel drive car ck the gear oil , sounds like it does not have enough fluid in it, that is what make that sound , good luck and let me know how you make out ,

the wheel bearing is OUT

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.

rear wheel bearing.

Sounds like the engine may have some worn bearings inside either on the crankshaft or the camshaft.

Then noise you hear after shutting off the car very well might be the air suspension compressor. The air ride system is still activated for a half hour after the vehicle has been shut off. The roaring noise from the rear could be a bad bearing. The rear axle seals don't always leak when a bearing goes out. So it's not a conclusive indication that they are good just because the seals aren't leaking. If your mechanic isn't too versed in differentials it may be advisable to seek an opinion of a reputable transmission shop (however, that may be a difficult task).

That roaring noise should be a wheel bearing. Jack up the rear wheels and spin the tires by hand. You can hear a grinding noise if the noise inside the car is as load as you state.. The only other noise that will be like that is the differental gears inside the drive axle

PINION BEARING ALSO CHECK FOR CHIPS IN THE PINION GEAR IF LET GO IT WILL TEAR UP THE REAR END IN WHAT EVER VEHICLE YOUR DRIVING