The differential is an important (and costly) part of your vehicle that transfers and manipulates engine torque being sent to the drive wheels. What’s more, the differential allows the drive wheels to turn at different speeds when cornering to prevent skidding.
Generally, differentials are quite robust. But if the differential in your vehicle fails, you’ll likely notice one or more symptoms that you’ll want to address right away.
What is a Differential?
Your vehicle’s differential is a complex assembly that transfers and manipulates engine torque being sent to the drive wheels. The differential uses a hypoid gear set—consisting of a ring gear and a pinion gear—to change the direction of the engine torque so that the vehicle’s drive wheels turn as they should. Torque is also multiplied by the gear ratio created between the ring gear and pinion gear.
Furthermore, the differential contains a collection of pinion gears and side gears housed inside of a carrier assembly. The pinion gears and side gears are collectively known as “spider gears”. The spider gears allow the drive wheels to rotate at different speeds so that the vehicle can turn a corner without skidding.
The ring gear attaches to the carrier assembly and the side gears spline to the vehicle’s axle shafts, which connect to the wheels. A variety of bearings support the various components within the differential assembly and allow rotation with minimal friction. The differential is filled with fluid to keep everything lubricated.
There’s a differential for each set of drive wheels. For example:
- Rear-wheel drive vehicles have one differential in the rear.
- Four-wheel drive vehicles have two differentials: one in the front and one in the rear. A transfer case assembly is used to divide engine torque between the front and rear differentials.
- On front-wheel drive vehicles, the differential is integrated into the transaxle and is often referred to as a “final drive assembly”.
- A typical all-wheel drive vehicle with a front-wheel drive-biased layout has a transaxle (with integrated differential) in the front and a stand-alone differential in the rear. A power transfer unit (PTU) divides engine torque between the transaxle and rear differential. There’s also a viscous coupler that prevents driveline windup.
The video below demonstrates how a typical differential works in a rear-wheel drive vehicle:
Common Signs of a Bad Differential
Do you think you might be dealing with a bad differential? If your vehicle is exhibiting one or more of the following symptoms, you might be right.
Note: Because other problems can present the same symptoms as a bad differential, you’ll want to perform a thorough diagnosis of the vehicle before performing any repairs.
Abnormal Noises
Abnormal noises are often one of the first signs of a differential problem. A whining or growling noise from the drive axle while driving can indicate an issue with the ring and pinion gear set or one of the differential’s bearings.
If the vehicle has a limited-slip differential—a design that continuously applies power to both drive wheels—sticking clutch packs within the assembly can create a chattering noise.
Issues within the differential can also lead to clunking noises. For example, damaged spider gears can cause a clunking sound while cornering, whereas damaged ring and pinion teeth can create a clunking noise while driving in a straight line. In addition, excessive backlash between the ring and pinion can cause a clunking sound on acceleration or while putting the vehicle into gear.
In some cases, you may notice that a shuddering sensation or a vibration accompanies the noises from the differential.
Fluid Leaks
Fluid leaks from the differential are usually caused by worn-out seals. But there are also instances where a faulty component within the differential, such as a worn-out pinion bearing, can cause a seal to leak.
Metal-Contaminated Fluid
If you look at the differential fluid and find it’s contaminated with a substantial amount of metal, the differential has likely failed internally.
Power Isn’t Transferred to the Drive Wheels
In instances where the broken differential suffers a catastrophic failure, engine torque may not be transferred to the drive wheels. As a result, the vehicle will be unable to move under its own power.
What Causes a Differential to Go Bad?
In some cases, the internal components within the differential simply wear out from normal use. Other common causes for differential failure include:
- Low fluid
- Contaminated fluid (for example, a differential that’s submerged in water could become contaminated)
- Larger than normal tires or mismatched tires
- Seized or severely worn u-joints
- An incorrect driveline angle
How Much Does it Cost to Fix a Differential?
Rebuilding or replacing a differential assembly is a costly and labor-intensive repair. If you choose to have a professional do the job, you can usually expect to pay somewhere between $2,000 and $4,000. Of course, the exact cost will depend on various factors, such as the year, make, and model of your vehicle.
Differential FAQ
You’ll want to address any differential problems as soon as possible. If the differential were to fail while driving, your vehicle could suffer additional damage, as we’ll discuss below.
The answer depends on what happens when the failure occurs. In a worst-case scenario, the differential could experience catastrophic failure and lock up, potentially causing damage to additional driveline components.
Also, if engine torque is no longer being transferred to the drive wheels, the vehicle may not move under its own power.
Although rare, a failed differential can damage the transmission. If the differential experiences catastrophic failure and locks up, other parts of the drivetrain, including the transmission, could be damaged as a result.
A failure of an internal differential inside of a transaxle can also cause damage to additional components within the transaxle assembly.
Where to Get a New Differential for Your Vehicle
A bad differential takes the fun out of road trips. On top of that, it puts your vehicle at risk of catastrophic failure if you don’t resolve it immediately. To avoid paying hundreds of dollars for repair jobs, you shop for a top-notch differential here at CarParts.com.
Precision-engineered and quality assured, our direct-fit differentials are guaranteed to get your vehicle running like it’s good as new. Enter your vehicle’s year, make, and model into our vehicle selector to view OE-grade differentials that fit your ride. Check out in a matter of minutes, and expect your order at your doorstep in as fast as two business days.
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