Your vehicle’s drivetrain has a fair amount of parts to it – but one of the lesser-known components is the rear differential. That’s mostly because in modern automobiles, the differential is extremely reliable, and rarely needs any repairs.
But when it does start to have problems, it is critical to diagnose and repair the issues as soon as possible.
In this article I will guide you through everything you need to know to diagnose a rear differential noise problem, as well as what you can expect if the rear differential is requiring repairs.
Diagnosing Rear Differential Noises
The first symptom that something’s wrong with your rear differential will be something that you hear. But people often misdiagnose rear differential noises and become worried, leading to a headache until the repair shop tells you what it actually is.
Let me walk you through everything you need to properly diagnose rear differential noises and, in some cases, keep you from going to the repair shop.
Wheel Bearing Noises vs. Rear Differential Noises
Wheel bearing noises and rear differential noises often sound the same, and this is why people often confuse or misdiagnose them.
Generally, wheel bearing noises are pretty common, so if you haven’t closed the noise down yet, you are likely in the clear and not dealing with a rear differential issue.
You can figure out if you are hearing a wheel bearing noise or a differential noise pretty easily. If you are driving at higher speeds (25-30 mph plus) and the noise changes when you turn (because the weight distribution of the car is changing), then there is no question it’s probably a wheel bearing and not the differential.
A wheel bearing noise will come from one of your axles, meaning it will sound louder on one side than the other side of the vehicle.
Ultimately, a rear differential noise will come from the differential housing. Unfortunately, you can’t just lay underneath the vehicle and pinpoint the noise, because you can only hear it when the car is moving!
Because of this, when you are trying to diagnose a rear differential noise, it is helpful if you have a couple people in the car to listen where it is coming from!
If you think you have figured it out, consider switching sides of the car. If it is noisier on one side than the other, it is a faulty wheel bearing and that is where it is coming from.
Common Rear Differential Noises
The most common rear differential noise is a whirring sound, but you could also have a clunking or banging sound as you accelerate.
Both noises indicate worn gears even though banging or clunking is very much worse and you want to get on it immediately.
Whirring is going to remind you of the sound of a worn wheel bearing – in fact, it’s the exact same sound – and in fact, worn bearing is far more common than worn gears, which is why they get misdiagnosed by people.
Whirring might not be as serious as banging or clunking, but it’s not something to ignore either.
Finally, you might also hear chattering. This happens when the teeth on the gears of your rear differential break. You won’t just hear it, though, you will feel it in the steering wheel.
The faster you’re driving, the louder the noise will be and the worse the vibrations will be in the steering wheel. This is a serious condition that you want to go after immediately.
You might think that breaking a single tooth tool is not a big deal, but it’s common for them to break 2-4 at a time, and breaking one tooth puts stress on the others, so more will break once the other is broken. Chattering can go from minor to failure quickly.
Rear Differential Damage Prevention
The single most effective way to care for your rear differential, and to diminish the likelihood of a repair, is by following regular service intervals. Like motors, rear differentials produce and operate on a thick oil (90-weight) to keep everything moving in the right direction.
That said, much like an engine oil, it will last a long time but will still need servicing at some point. Regular service intervals will significantly decrease the likelihood of you needing to rebuild or replace your rear differential.
That being said, the result of never following the regular service intervals is that you will ultimately be spending a considerable profit on repairs, you know how it goes.
Rear Differential Repair Costs
The average cost of fixing a rear differential is anywhere from $500 to $2,000 based on the type of vehicle and what shop you take it to.
This is a huge range, because rear differentials come in so many different sizes, and you have to consider the particular issue with your rear differential too.
You might be thinking you can rebuild or repair your rear differential yourself, just know it is one of the more complicated parts of a vehicle, and it is quite easy to screw something up.
You can do it if you know what you are doing, but you should seriously consider using a certified repair shop instead of potentially screwing up and causing even greater expense.
What Happens If You Don’t Repair a Damaged Rear Differential?
Once you discover that your rear differential is faulty, it can be tempting to run the problem out for the longest possible time. Rear differential repair often is an expensive repair. However, the danger of driving with a worn or broken rear differential cannot be overstated.
As more teeth break and gears wear down, everything is going to start slipping, and the rear differential internals will start to “chatter” as you are driving down the road. This slipping and chattering is more than simply irritating – it can affect the stability and control of the vehicle.
In the worst-case scenario, you can have an accident. And since vehicle control will be worse with more speed, it is probable you will have an accident traveling at higher speed which translates into a higher likelihood of serious injury to you or someone else in the accident.