2002 Yukon XL what is the cause of rear differential howling and how do you fix it?

The most common cause of howling in a rear differential is worn bearing . When diagnosing a howling differential its also wise to check the ring and pinion gear clearance along with the backlash to ensure that the backlash of the ring and pinion is within the recommended settings. It is always a good practice to check for any foreign debris in the differential itself. Once you have established that there is no foreign debris in the differential and the ring and pinion gears are within the proper settings then replacing the bearings will most likely resolve the howling differential.