The main symptom of a bad differential is noise. The differential may make noises, such as whining, howling, clunking and bearing noises. Vibration and oil leaking from the rear differential seal may also be signs of a failing differential.
A steady whining or grinding sound that increases in intensity with the speed of the vehicle is the most commonly reported symptom of a failing differential. This sound typically indicates worn gears, under-lubricated gears or gears that are out of alignment with each other.
Another common sound is a banging or clunking sound while turning a corner. This symptom can also be related to insufficient lubrication, broken spider gears or worn components, such as positraction or clutches. Broken spider gears can cause the differential to freeze and make a noisy crunching sound. Clunking every few feet, rather than just on corners, may indicate that there is a broken ring gear.
A heavy clicking sound that occurs every 8 feet or so indicates a chipped or missing high spot on a gear tooth. If the problem is on the pinion, the clicking sound occurs every few feet and has a higher frequency sound.
Noise in the differential is never a good sign, and any persistent or unusual sounds in that area need to be checked out immediately.