5 Leaking Differential Symptoms & How to Fix

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Edgar Moulton.


Edgar Moulton. Car Expert

A leaking differential can lead to a broken differential. A broken differential can lead to expensive repair or replacement costs and even dangerous driving situations! Read on to see the symptoms of a faulty differential and what you can do with a car with a damaged differential. 

5 Symptoms of a Differential Leak

#1 Strange noises

A bad differential sounds much worse than a normally functioning one. If you hear grinding or rattling, especially from the back of your car, it could mean you have rear differential problems. Grinding or rattling coming from the front of your car could also be your transmission, but it is definitely one of the more common bad differential symptoms, and you should definitely have it looked at by a mechanic. 

#2 Strange smells

Differential oil (also called “gear oil”) is thicker than motor oil. This means that when it goes bad, it goes bad quickly, and many bad things can happen to your differential once it goes. Because it’s already thick, when it thickens even more, it heats up, and the gears have more friction, creating more heat. This will cause your differential oil to smell bad. Any time you smell burning coming from your car, it’s time to get it checked by a mechanic because it will lead to bigger issues down the road. 

#3 Poor handling

The differential helps your vehicle handle by keeping the wheels on either side of the axle spinning at the correct speed. (This is true even on the rear axle differential, even though they’re not the wheels steering your car.) If your car isn’t handling correctly, it might be because of a faulty drive differential

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#4 Vibrations

A differential without sufficient gear oil will cause the gears to mesh together not as smoothly as they should. This will sometimes cause the car to vibrate while driving along, particularly during turns. Vibrations can be a sign of a faulty differential or many other serious issues with your car. It’s definitely time to get your car checked out by a mechanic if you feel vibrations. 

#5 Leaks

Differential oil can leak from the gasket. Sometimes it’s a slow leak (seep), or sometimes it leaks quickly enough to drip. If you suspect an issue with your differential, check for leaks. Read on for how to check for leaks. 

How To Check if Your Differential is Leaking

Every car has a differential (sometimes called a “diff”). A rear-end differential is found on cars that are rear-wheel drive. Front-wheel drive cars have a front-end differential (sometimes called a transaxle). Cars with four-wheel drive have both, which means you’re prone to a rear differential leak as well as front differential leaks. There are two main ways to check for a leaking differential. 

Differential oil under your car

Checking differential fluid should really only be done by a trained mechanic, but you can look out for signs. If you have rear-end differentials, you will find an oil leak under your car's rear axle. If your front diff is leaking, it’s a bit more complicated because that’s where other leaking fluids from the engine bay will appear as well. If you just find oil on the ground underneath the front of your car, it could be differential fluid, transmission fluid, or motor oil. If you have a front-wheel drive car and find a leak in the ground in the front of your car, have a mechanic check your differential oil. (Especially if you have symptoms of a bad differential, like front diff noises.)

Leaking rear differential gasket

The best way to find a leaking differential transmission is to check around the gasket. You’ll find this on the underside of the differential housing, and if you find oil leaking from it, you have a worn-out gasket. This means your gasket is leaking fluid, and it’s only a matter of time before it turns into a bigger problem. If you have a rear diff leak, you will find the oil drips right in the middle of the two rear wheels

What Causes a Rear Differential to Go Bad

The main cause of a differential gone bad is too little gear oil. The gear oil keeps the gears lubricated and prevents them from creating too much friction and heat while the spider gear inside the differential is spinning. This heat and friction will eventually cause the metal gears to grind down and lead to a broken differential. Another cause is just putting it through hard use. If you have modified your car to have more horsepower than it’s designed to have, or you do burnouts or drag racing, it’s a sure way to kill the lifetime of your differential. 

What Can Go Wrong If I Drive With a Bad Differential

What can go wrong while driving with a bad differential depends on how severe the problem is. Vibration isn’t that dangerous or even annoying while driving, but if it’s from the differential, it means it’s time to get it looked at and fixed. If you have badly chipped gear teeth or broken gear teeth, you will experience a skip or slip in power while driving. This gets worse the faster you drive. 

In more severe cases, driving with a faulty differential will create problems with the way your car handles around turns. The tighter the turn, the more you will feel the handling issues. In very extreme cases, a broken differential can even leave you stranded. 

What to Do If the Differential Is Leaking

The first step in deciding what to do about a leaking differential is to decide how bad the leak is. If it’s just slowly seeping (the bottom of the differential housing has a little bit of gear oil on it, but not dripping), it’s best to just keep an eye on it to make sure it doesn’t get worse. (Also, pay attention to any of the symptoms we mentioned above.) 

If it’s actively dripping, it means it’s a pretty severe leak, and eventually, the differential will run out of gear oil. When this happens, your differential will die fairly quickly. If it’s already making the car vibrate or handle poorly, it’s time to decide if you want to spend the money on repairing or selling your broken car to us at JunkCarsUS. 

If you already hear grinding noises coming from the differential or it’s completely gone out, and your car has left you stranded, we have good news and bad news. The bad news is that it will cost you to repair it. The good news is if you don’t feel like repairing it, we buy wrecked cars so that you can change that repair bill into cash in your pocket. This very well maybe your best financial option if the diff is broken and the repair bill is more expensive than the car is worth. 

Repair or Replace a Leaking Differential?

Should you repair or replace your leaking differential? This largely depends on how bad the damage is, how many miles have been put on the car, how hard the car has been driven, and the overall value of the car. Rebuilding your differential is an option and usually costs somewhere between the repair and replacement costs, but you will still be putting money into the car. 

How to Fix a Differential Leak

Fixing a differential leak isn’t an easy process if you’re not a mechanic and don’t have the right tools. You’ll need to jack the car up and get underneath, so if you’re not comfortable doing that (and that’s only the first step!), it’s best to let a trained mechanic do this for you. Beyond that, you will need to unscrew and remove the cover and gasket. While it’s open, you need to drain the gear oil, clean the inside the differential, replace the gasket, and put the differential cover back on. Then you need to fill the differential with new gear oil and take the car for a test drive while looking out for all the things that could go wrong. Again, it’s a pretty complicated process and should be done by a mechanic. 

Average Repair Costs

Basic front differential leak repair costs (like replacing the gasket or adjusting the backlash) will cost you between $200 and $400. If you have ignored the warning signs we mentioned above and there is a lot of damage, it will run you between $400 and $800. This price includes parts and labor. 

A front differential replacement and rear differential replacement will cost about the same, but that doesn’t mean it’s cheap. To completely replace a differential, you will spend at least $1500 and all the way up to $4000, depending on the model of your car. 

How To Prevent Severely Damaging Your Differential

The best way to prevent breaking your differential is by getting regularly scheduled maintenance. Your differential, just like any other part of your car, requires regularly scheduled maintenance, and ignoring this will decrease its lifetime (and the rest of the parts you ignore)! 

On top of that, differentials don’t just go bad out of nowhere. There are warning signs (like the symptoms we mentioned above). If you notice any warning signs, it’s best to get them checked out as soon as possible because ignoring them will surely lead to the problem getting even worse the more you drive it. Once it reaches that point and breaks, you’ll have to replace the whole differential. 

Junkcarsus is a Trusted Junk Car Buyer Working for 12 Years

If you have a car with a broken differential that needs a front or rear diff replacement, it’s time for you to decide if it’s worth the cost of if it’s cheaper and easier to get rid of it and get cash to put towards the purchase of a new vehicle

At JunkCarsUS, we take nearly any car in any condition and buy it from you for cash on the spot! We can give you an instant top dollar offer. We even offer the highest price guarantee of all the junk car buyers in the USA. We even offer same-day service with free towing. 

Getting rid of your junk car is as easy as 1, 2, 3 with JunkCarsUS.  With over 12 years in the junk car buying industry, we have developed a simple 3-step process that makes junking your car completely hassle-free. 

  1. Call us at (855) 547-1550 and speak to one of our friendly customer service representatives. Give them the make, model, year, condition, and mileage on your car, and we’ll give you a cash offer on the spot. Or go on our website and get your instant offer from our scrap car value calculator
  2. Once you accept your cash offer, tell us the time and place that’s most convenient for you for us to pick it up.  We’ll send one of our trusted and safe tow truck drivers to meet you on time, even on the same day if you’re in a rush to get rid of it.
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Because we’ve done this so many times, our employees know exactly what we have to do. This means we do the paperwork for you. That’s right, no paperwork. The process of getting rid of your junk cars couldn’t be any simpler. So give us a call at (855) 547-1550 or fill out an online application and trade your junk car for cash today!


What are some rear differential failure symptoms?

A failing rear differential will give you some warning signs before it completely dies out. These include vibrations in the car, poor car handling (especially during turns), grinding noises, and a leaking gasket.

What causes a rear differential to go bad?

The main thing that causes a rear differential to go bad is not keeping up with regularly scheduled maintenance. Aside from that, high mileage cars have a lot of wear and tear, and driving your car hard will increase the amount of wear and tear on the differentials.

What happens if the rear differential goes out while driving?

If your differential goes out while driving, it’s bad news. You will hear a loud bang and lots of grinding noises, but on top of that, it could get you in a hazardous situation because the vehicle’s handling will be negatively affected. On top of that, you can’t drive a car with a broken differential, so you may get stranded if the differential goes out while you’re driving.

How do I check the rear differential fluid?

If you suspect you’re having differential problems, checking the fluid is the first step to take. If you see oil droplets on the ground underneath the axle of your car, it’s a good time to take a look at the differential housing. If you see oil dripping from the bottom of the housing, it’s a clear leak. Sometimes slow leaks won’t drip but will seep slowly, and you’ll find just a small wet spot on the bottom of the differential housing.

How do I repair a differential leak?

If you’re not mechanically inclined and don’t have the necessary tools, it’s best to have a trusted mechanic do it for you. This is because it involves jacking the car up on stands, removing the diff cover and gasket, cleaning it out, replacing it, then refilling it with gear oil. This is more difficult than what the average person can do themselves.

Edgar Moulton.


Edgar Moulton. Car Expert

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