BMW 33102227925 Differential

What if the differential results in a low pitched rumbling sound, the first way is to examine the fluid level, type and quality, the second way is to drain the fluid and replace it with a recommended lubricant. Also, check the differential bearings and remove it to check the drive and the driven gears, other components should also be replaced if damaged. For howling noise from the differential also check the level of, kind of and quantity of lubricant, replace with recommended lubricant for the differential, Examine the differential drive and driven gears for signs of wear or damages replace with the new as advised.