Your rear differential is a mechanism in your vehicle that enables the crankshaft to create torque before it is distributed through the transmission to the driveshaft and wheels.
Overall, the rear differential transmits engine power to the wheels and allows them to have different rotation speeds – especially during a turn. Your driving wheels do not rotate at the same speed during a turn because the inside wheel rotates slower than the opposite outside wheel.
The rear differential decides the speed and frequency of the turning of the axle and wheels in relation to the driving shaft to ensure stability.
When one wheel is spinning slower on a curb, for example, the rear differential will keep driving the other wheel and prevent skidding, binding, or jerking. Without a differential, the wheels would lock together at the same speed during a turn and increase the likelihood of losing control.
Other than turning, not having a rear differential could cause issues with the drivetrain being exposed to high forces, causing one tired to grab and slip in order to maintain the same speed as the other tire. This puts a huge strain on axle components and can lead to premature tire wear.
What is a Differential?
A differential (often called a diff) is a gear train that transfers power from the engine to the driven wheels of a vehicle. Diffs also allow the wheels to rotate at different speeds while cornering, which is crucial for vehicle handling and performance.
In most cases, the differential is located on the rear axle. It translates longitudinal power from the propshaft into latitudinal power across the rear axle or driveshafts.
Rear-wheel drive, all-wheel drive and four-wheel drive vehicles have a rear differential. Front-wheel drive vehicles (as well as some types of rear and four-wheel drive vehicles) use a transaxle, which combines the functions of a differential and transmission.
Transaxles and alternative differential arrangements are subject to the same stressors as conventional differentials, so they require regular servicing to prevent breakdowns.
The Function of a Differential
When you corner your car, the right and left wheels take different paths. The inside wheels require a smaller turning radius, meaning fewer revolutions are needed.
Without a differential, the tires would need to spin at the same speeds, even though they need to be on different paths. This condition would cause one of the tires to slip, creating less traction, wear on the powertrain and uneven tire wear.
The tire speed difference is determined by the track width. This term describes the distance between the left and right tires.
As the track width gets greater and the turn becomes tighter, the speed difference between the wheels increases, causing the differential to do its job.
The Importance of a Properly Functioning Differential
A bad differential can cause uneven tire wear and less traction. It can also damage your drivetrain and cost a lot to fix. Regular checks can spot differential failure indicators like grinding sounds or vibrations.
Knowing if a differential is bad early can stop big problems. Keeping your differential in good shape means smoother rides and longer life for parts. This saves you money on repairs later.
Types of Rear Differentials
There are four main types of differentials used in vehicles today.
Open differential
Open differentials are the most basic and allow for variations of individual wheel speed. They transfer torque even if the wheel has zero traction, resulting in a spinning tire.
Limited-slip differential
Limited-slip differential acts like an open differential but prevents tire slipping when cornering hard or accelerating. These are most commonly found on race cars.
Locking differential
Locking differentials are mainly found on off-road vehicles and some performance cars. They use clutches and springs to activate a lock to send equal amounts of power to each wheel no matter the traction situation – this allows them to gain a great amount of traction.
Torque-vectoring differential
Torque-vectoring differential is the most complicated and advanced type of rear differential.
This differential uses sensors and electronics to gather data such as road surface, throttle position, etc. to active electronically controlled clutches.
Symptoms of a bad differential
Knowing the symptoms and signs of a failing or broken differential will help you address the problem promptly and ensure you’re safe while on the road. Here’s what to look out for:
#1. Noises.
Whining or whirring noises can be a sign of a failing differential. You might notice them more when you accelerate, slow down or navigate a corner.
Howling and humming sounds can also indicate problems with your differential’s components, such as worn-out bearings in the axle or damage to the drive pinion.
You may also notice a clunking or a clicking sound when you’re out on the road, turning, or using the accelerator pedal.
#2. Overheating.
Driving your car at high speeds for a long time, or hauling heavy objects, such as a caravan or trailer, can put extra pressure on your differential, causing it to overheat.
That can then cause parts of the differential to break down. The same issue can happen if you let your car wheels spin out a lot, causing damage to the differential.
#3. Vibration.
If you feel a vibration that gets more intense as you accelerate, inspect your differential as soon as possible.
Even if it’s not the differential causing the vibration, this is a symptom you should never ignore. If you’re not sure what’s causing it, have a mechanic give your vehicle a once-over.
#4. Handling/steering problems.
You might notice problems or difficulty handling the wheel of your vehicle, especially when cornering. If your vehicle is hard to control while turning or pulls to one side, it could be a symptom of a failing differential.
#5. Gear grinding.
Grinding sounds may also mean that the internal gears within the differential system are wearing out. Again, it’s more likely to happen when accelerating or turning a corner.
#6. Tyre damage.
The lack of control a failing differential has over your vehicle’s tyres will eventually show in the tyres themselves. Look for excessive tyre wear, uneven treads, or damage along the outer tyres.
#7. Oil leaks.
Your differential has gear oil to keep all the components working smoothly together. It also maintains temperature when you’re out on the road. You may notice fluid pooling under the axles if it springs a leak.
#8. Out-of-balance driveshaft.
If the differential is failing to transfer the right torque to the wheel, it can result in a propshaft that’s out of balance.
You might notice your vehicle shuddering, have difficulty turning, or feel vibrations from under the vehicle, as well as all those noises that indicate something is wrong, such as squeaking, clicking or knocking.
#9. Burning smell.
A burning odour from the gearbox indicates that your differential oil is dirty or contaminated, and so it’s not keeping all the components running smoothly. This then causes the gearbox to overheat, resulting in a pungent smell.
causes of bad differential
Since the differential is not a complex but a simple mechanical device, few symptoms can cause it to fail. Let’s explore these causes.
#1. Lack of Lubrication.
Insufficient or contaminated differential fluid can cause excessive friction and overheating, leading to premature ear and failure of the differential components.
#2. Overloading.
Frequently carrying heavy loads or towing beyond the vehicle’s capacity can strain the differential, causing stress on its gears and bearings.
#3. Abrasive Contaminants.
The presence of dirt, debris, or metal particles in the differential fluid can cause abrasive damage to the gear surfaces and bearings.
#4. Neglected Maintenance.
Failure to perform routine maintenance, such as fluid changes and inspections, can allow small issues to escalate into more significant problems over time.
#5. Severe Driving Conditions.
Repeated exposure to harsh driving conditions, such as off-roading, extreme temperatures, or frequent stop-and-go traffic, can accelerate differential wear and increase the risk of failure.
#6. Manufacturing Defects.
In rare cases, manufacturing defects or poor-quality components can lead to differential failure, even with proper maintenance and usage.
#7. Incorrect Gear Ratio.
Incorrectly installed or mismatched gear ratios in the differential can cause excessive stress and wear on the components, ultimately leading to failure.
#8. Accidents or Impact Damage.
Collisions or impact damage to the vehicle’s axles or differential housing can result in internal damage to the differential components.
#9. Age and Mileage.
As vehicles age and accumulate mileage, the differential components naturally wear out, making them more susceptible to failure.
Differences Between Front And Rear Differential Problems
Front and rear differentials do different jobs. So, their problems show up in different ways. Knowing these differences helps you find the right fix.
Front differential issues often show up when you turn. Rear differential problems might get worse when you speed up.
Front differential issues often include:
- Noises like clicking or whining during tight turns
- Steering drift or uneven tire wear on the front wheels
- Difficulty maneuvering at low speeds, like parking
Rear differential failures commonly show as:
- Strong vibrations felt through the floorboard during high speeds
- Grinding sounds when accelerating hard or shifting gears
- Visible leaks near the rear axle or driveshaft
Front-wheel-drive cars often mask front differential issues as suspension problems. Rear differentials in trucks may cause noticeable thuds when backing up.
Front differentials in FWD vehicles handle steering and power. So, if they’re off or worn, turning gets tough. Rear differentials in RWD cars manage torque.
So, leaks or grinding sounds mean damage. All-wheel-drive systems mix both, making finding the problem key.
How to Repair a Bad Differential?
To repair a faulty rear differential, it is important to evaluate the situation properly. Then you can identify the issues to address, be it a worn-out or damaged component.
It’s critical to understand that rear differential repair is not a straightforward process and can be relatively dangerous.
#A. Diagnosis and Inspection.
The first step to take is identifying what kind of problem you are facing. To do this, you might need to test drive the car to experience the symptoms in real-time.
After that, a visual inspection is necessary. Check for leaks, physical damages, and evidence of wear and tear.
#B. Fluid Inspection and Replacement.
Check the differential fluid level and condition. If the fluid is low, contaminated, or in poor condition, drain it. Replacing the drained fluid with manufacturer-recommended fluid can sometimes resolve specific issues.
This step can also provide an opportunity to inspect the fluid for metal shavings or debris, which could indicate internal component damage.
#C. Seal and Gasket Replacement.
If the differential leaks fluid due to damaged seals or gaskets, you must replace these components. Proper sealing is also crucial to maintaining the correct fluid levels and preventing contaminants from entering the differential.
#D. Bearing Replacement.
Worn or damaged bearings can cause excessive rear differential noise and vibration. If bearings are the issue, you will need to replace the bad wheel bearing. It usually involves disassembling the differential to access and replace the bearings.
#E. Gear Replacement.
In cases where the gears within the differential are worn, chipped, or damaged, you will also need to replace the gears. This process can be more complicated, requiring disassembling the differential and replacing the affected ones.
#F. Professional Repair or Replacement.
For more severe damage or when multiple components are compromised, consult a professional mechanic or a specialized shop that deals with auto repairs.
They can accurately diagnose the issue, recommend the appropriate repairs, and perform the necessary work with the right tools and expertise.
#G. Complete Differential Replacement.
Certain scenarios could result in significant differential damage, so pursuing repairs becomes more expensive than a complete replacement. In this case, installing a rebuilt or brand-new differential unit is a more practical solution.
#H. Reassembly and Testing.
After you’ve made the necessary repairs or replacements, the differential will be reassembled and adequately torqued to ensure optimal functionality. You can test drive to help verify that the issues have been resolved and that the differential operates smoothly.
If you’re not experienced in working on drivetrain components, then it’s recommended to seek assistance from a qualified mechanic or a reputable repair shop. This ensures the proper diagnosis and repair of underlying issues.
What Does a Differential Replacement Include?
A differential replacement typically includes the following:
- Removing the damaged or worn-out differential assembly.
- Installing a new or rebuilt differential unit.
- Reconnecting axles, driveshafts, and related components.
- Refilling the differential with the appropriate fluid.
- Testing the vehicle to ensure proper operation and alignment adjustments if necessary.
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 Maintenance Tips
- Regularly change the differential fluid according to your vehicle’s service schedule.
- Inspect for leaks and address them promptly to prevent fluid loss.
- Avoid overloading your vehicle to reduce stress on the differential.
- Perform routine vehicle maintenance to prevent excessive wear on differential components.
- Use the correct type and grade of differential fluid recommended by the manufacturer.
- Follow proper driving techniques, avoiding sudden or aggressive maneuvers.
- Keep tires properly inflated and ensure even tire wear to reduce strain on the differential.
- If you hear unusual noises or notice symptoms of differential problems, address them promptly to prevent further damage.
FAQs.
Q: What happens when your rear differential goes out?
Typically, the differential will start giving strange noises when it goes out or when the bearing fails. You will hear a whirring, whining, growling, or howling noise.
The noise will increase or decrease as you accelerate or decelerate the vehicle. Sometimes, you may not hear the noise when you step on the throttle panel.
Aside from these noises, you may experience difficulty in handling, vibration, differential overheating, and, in some cases, a burning smell.
Q: What noise does a bad rear differential make?
A bad rear differential will develop a series of strange noises. It could be a whirring noise, a humming noise, a growling noise, or a whining noise.
However, the most common sound of a bad differential is a whining or howling noise, indicating a damaged or worn-out ring and pinion gears.
Q: Can you drive with a broken rear differential?
You can still drive your vehicle with a bad rear differential, but it can cause severe damage. The problem may increase to the point of stopping you in the middle of nowhere.
And, if you are asking about driving with a total broken differential no, don’t do it unless you want to damage the entire drivetrain system.
Q: How often should you flush your differential?
Automakers have different replacement and service intervals for each component, and differential flush is no exception.
However, most automakers recommend differential flush every 30,000 to 60,000 miles. It is a messy job and should be done by a skilled mechanic.
Q: How long do differentials last?
The lifespan of a differential depends on various factors, such as driving habits, level of maintenance, the type of oil used during servicing, and many more.
Under regular use and proper maintenance, differentials should last 150,000 miles or the life of a vehicle.
Q: Can a bad differential cause a transmission problem?
A differential has one significant function; to transfer power from vehicle transmission and engine to individual wheels.
The differential allows the driver to optimize the handling and control of the vehicle. It offers more precise control over your wheels instead of the wheels to be turning at the same rate.
Final Words
It doesn’t end at knowing the symptoms of a bad rear differential but knowing bad pinion-bearing symptoms and figuring out the problem on time. Once you figure out the fault, the next thing is to contact your mechanic for a proper diagnosis and fix.
At this juncture, I believe this content has uncovered the signs of a failing differential, its causes, how to prevent it from happening, and important tips and tricks of prolonging a differential life.