When it is functioning normally, your differential should make very little noise. But when you start hearing unusually loud noises originating from your differential, you should know that something is definitely amiss somewhere. If you hear louder than usual differential noise when you are driving, you should never ignore the issue because it may mean that your differential is in trouble and needs repair service. Here is a useful troubleshooting guide for noisy differentials.
Howling sound while accelerating the car
If your gears were previously quiet, but there's now a steady howling sound (with or without rumble) that increases when you accelerate the vehicle at any speed, your rear pinion bearing or gear set could be worn down due to excess loading or under-lubrication. If you replace the worn parts but you can still hear the same annoying sound, check to see if the gear teeth are properly aligned.
Whirring sound while decelerating the car
Differential noise can also be heard when you are slowing down at various speeds. Usually, you will hear a "whirring" sound coming from the rear of your differential. In most cases, this is a sure-fire indication that your pinion bearings are either loose or overly worn and need to be repaired or replaced. Pinion bearings create a whirring noise because they rotate several times faster compared to the carrier assembly. If you hear more of a clicking noise than a whirring noise when you are decelerating the vehicle to a stop, overly worn carrier case-side gears could be the cause of the noise.
Rumbling while turning the car
Another type of differential noise you may hear is rumbling while you are turning your vehicle in sharp circles, and the typical culprit is bad wheel bearings. If the problem is the wheel bearings, they will have to be removed and replaced. But the rumbling could also mean that your differential fluid has broken down and needs repair service. In this case, the repair work will involve draining the old differential fluid, locating and fixing any leaks, and then adding fresh fluid.
A failed differential can be very expensive to replace, so you are better off seeing a mechanic immediately you learn that your differential is noisy. Even if the problem is not with your differential, your mechanic will diagnose the exact source of the problem. Generally speaking, any unusual noises coming from any part of your car should never be ignored.