A car's differentials are a set of gears that allow the wheels of the car to spin at different speeds. This is needed when you turn; the inside wheels are traveling less distance than the outside wheels and without differentials that slow down those inside wheels, the car might easily drag, spin out of control, or resist the turn altogether. The differentials are part of the car's entire drive train system, and it's good to know how to diagnose some common problems you might have with these gears and the system itself so you can know what to expect by way of needed repairs.

Heavy or loud clicking

If you hear a heavy or loud clicking sound, and especially if it happens intermittently and when you turn, this often means that the teeth of the differentials or other parts of the drive train gears are worn down. When the teeth of one gear are worn, they don't mesh very easily with other gears. In turn, you will hear them rub or bump up against them and this sounds like a clicking noise. This often happens intermittently as it may be that only a few teeth of the gears are worn, so you only hear the sound when those teeth are trying to mesh with other gears. A mechanic can usually check the gears of the differential or drive train in the area where you hear the sound in order to pinpoint its location.

Rumbling

When you hear rumbling from any wheel of the car, this often means that the bearings of the differentials or drive train are bad. If the rumbling gets worse during hard turns, this is also indicative of bad bearings. These are like metal balls that allow wheels to move left and right and not just straight ahead, and which also allow gears to turn smoothly. When the bearings go bad, you hear a rumbling as they mesh against each other.

Howling sound

If you hear a loud howling from a wheel or side of the car, this doesn't mean it's haunted! Usually the gears are not aligned properly and this howling occurs when air slides through an area where the teeth should be meshed together. It may be that a gear of the differentials is worn down or they may be misaligned. If your tires are not properly balanced or any other part of the drive train is damaged, this can cause the gears to be misaligned. In some case they can be adjusted or they may simply need to be replaced.