Car Differential Problems: 5 Common Issues & Solutions

Your car differential transmits the power from your engine and transmission to the wheels and tires. It takes a lot of abuse, which means it can have a lot of issues.

It may seem like a simple part of the car, but it is a complex assembly of smaller components that can be affected by nearby systems. It can in turn cause many other problems.

If you have never experienced a differential problem, we’ll cover the most common issues and how to fix them so you can be prepared if that situation arises in the future.

#1 – Your Differential Is Making Too Much Noise

The differential in your car, whether it’s in the front or rear of the car, shouldn’t make a lot of noise.

If you can hear it howling, clunking, or making a chattering noise, the differential has a major problem that needs to be investigated.

How to Fix It

Your car differential is a complex unit. It contains gears, clutches, springs, bearings, and all need to work together effectively.

The type of problem you have will indicate what you should initially investigate as the problem.

The differential should contain gear oil that keeps all components lubricated. The differential housing should have a fill port on the exterior that can be checked for the oil level.

Typically you can remove the plug threaded into the fill port and use the tip of your finger to test where the oil level is. The oil level should be around the fill port. If you can’t touch the oil in the differential, the oil level is low, and it should be filled with oil until it starts to pour back out of the fill port.

If the differential oil hasn’t been changed previously, or the car’s mileage is near the maintenance interval for the differential, it may be a better option to have the differential oil changed.

Low differential oil is a common problem when hearing a whining sound because the oil lubricates the gears and adds a thin film of oil to the bearing surfaces.

A low oil level allows the metal bearing surfaces to touch rather than riding on an oil film, which can howl due to the contact. If the oil level is low, you need to investigate and remedy the leaking point of the oil. It’s most likely dripping from the housing or at the end of the axles where there is an additional rubber seal.

Checking the oil level gives you an additional source of information concerning the status of the differential. If you have oil in the differential, you can check the clarity and contamination of the oil. If you find metal flakes in the oil, you may have a bearing or multiple bearings that need to be replaced due to excessive wear.

The differential uses multiple bearing sets to support each component inside. Carrier bearings support the final drive gear and can howl and rumble above 20 miles per hour and you may hear a change in tone or pitch as the car is turning.

Wheel bearings can exhibit the same howling and change in pitch when turning, but the source of the sound will be at the end of the axle near the wheel rather than inside the differential housing.

The last major howling suspect is usually a loose or worn pinion bearing that doesn’t have proper preload. It will howl when decelerating and no power is being applied to the car. Think of it as howling when you’re slowing down to stop.

If the sound you hear is more of a clunking, it could indicate the gears inside the differential are worn or have broken teeth. The pinion gear and spider gears mesh together as the differential spins inside the housing.

If any of them have one or more broken teeth, the gears won’t mesh well and can make a clunking sound.

#2 – Your Differential Wasn’t Properly Broken In When New

It’s a great feeling when you buy a new car.

The manufacturer recommends a break-in period for the powertrain to allow oil to be absorbed into every surface and to properly penetrate every bearing.

If you don’t follow the break-in procedure, you may unknowingly cause your differential to overheat and damage internal bearings and clutches.

How to Fix It

There’s always a temptation to get into your new car and immediately test its limits. You may want to take it on a long road trip keeping high speeds for a long time or to try and haul something heavy. It’s best to keep those activities scheduled after the break-in period.

That may be as little as 500 miles or 1,000 miles. You will also want to vary the driving speeds with a mix of stop-and-go traffic as well as highway traffic. This will ensure everything gets a proper break-in and it won’t cause future problems.

#3 – Your Tires Constantly Wear Out Quickly

Most attribute tire wear with problematic suspension alignment settings, but your differential can cause premature wear and an excessive amount of wear on your tires.

How to Fix It

Your differential contains clutches that should allow the tires to spin at slightly different speeds when you’re turning. The inside tire (left tire in a left turn, right in a right, etc.) doesn’t need to rotate as much as the outside tire to navigate a turn. The clutches allow the tires to rotate at different speeds during a turn.

When the clutches are worn, they may not slip and allow the tires to rotate at different speeds. This causes the inside tire to spin than needed and wear the surface.

You may not realize this is happening, but over time, the tires will wear out faster than expected. The wear pattern will be consistent across the tread width, but the edges may have slightly more wear.

When you discover excessive wear, the differential clutches need to be inspected and replaced if they have worn out.

#4 – Your Differential Vibrates When Driving

You may feel a vibration in the shifter or the seat of your pants when driving if something is out-of-balance or worn out.

The question is what has changed because excessive vibration isn’t a design in feature from the manufacturer.

How to Fix It

Most components in the engine and transmission are delicately balanced to prevent excessive vibration.

If you can feel a vibration through the shifter of the transmission or through the seat or floor (basically from the car itself), the most likely cause will be an out-of-balance driveshaft or worn universal joints (abbreviated as “u-joints”) on the driveshaft.

The drive shaft is balanced at the time of manufacturing, and it has weights adhered to the surface at specific spots to balance the shaft as it spins. These balancing weights can be lost over time, which causes a vibration to occur.

The shaft will have a natural harmonic to it, which can make the vibration seem more prominent during acceleration and deceleration and at specific road speeds. You can remove the drive shaft and have the balance checked at a driveline shop in your area.

Also note that a change in materials, such as replacing a steel drive shaft with an aluminum or carbon fiber one, can contribute to a change in the amount of vibration and the frequency of vibration that reaches the passenger cabin.

#5 – Your Car Has Poor Steering and Handling

Poor steering and handling are often attributed to a suspension issue, but the driving force to your tires goes through the differential. A failing differential can negatively affect how your car steers and handles.

How to Fix It

A failing differential can cause difficulty in steering which can negatively affect the handling of your car. It can cause your wheels to turn at slightly different speeds due to the internal clutches being worn out or bearings that are causing a drag on the axles.

At slow speeds you may not notice the poor steering, or that your car pulls to one side of the road, but at a high rate of speed there may be a clear indication that something is causing poor steering.

If a suspension and alignment shop in your area can’t find anything wrong with alignment settings, the cause may be your differential needs attention.

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