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What You Need to Know About Your Front Differential

What You Need to Know About Your Front Differential

Is your car or truck front-wheel drive or 4x4? Then you have a front differential. This special gearbox has an important function to perform to get your wheels turning. So buckle up while we take a closer look at this important piece of your vehicle!

What Is a Front Differential?

Simply put, a front differential is the part of a vehicle that splits the power and torque to the front wheels. Front differentials are located on the vehicle’s front axle. Mechanically, it’s nothing more than a series of gears.

So why are they so important? They’re absolutely critical for front-wheel-drive cars or 4x4s because they allow your front wheels to turn at independent speeds, a necessary process when doing things like making turns.

Think about it – when making a turn, your outside wheel needs to travel a longer arc than your inside wheel, requiring it to move faster to keep your vehicle turning correctly. At the same time, you preferably would like to keep both wheels turning from the engine.  

Front Wheel Drive - FWD - Explained

Is the Front Differential Part of the Transmission?

This answer will depend on the design of your vehicle. If your vehicle is a front-wheel-drive or all-wheel-drive model, your front differential may or may not be part of your transmission. Consult your vehicle’s manual or check online for specific information. Even if your differential is part of the transmission it usually has a separate oil reservoir that may need servicing. This is common in AWD vehicles like Subarus.

There’s a more definitive answer for owners of 4x4s. In all cases, the front differential of a 4x4 vehicle will be separate from the transmission.

front diff
Front differentials help your tires turn in tandem while driving.

What Are the Signs of a Bad Front Differential?

One of the easiest ways to know whether you’re having issues with your differential is trouble steering or making turns. If your vehicle isn’t handling exactly as it should, this may be the issue.

A bad front differential will also make quite a bit of noise. If you’re hearing grinding, clunking, howling, or shrieking while you drive, it may be a problem with your differential. Do the sounds change pitch when you apply or remove power, this is a common differential noise.

This is what happens when your pinion preload losens up: Rear end Noise
This is our rear differential but the same can happen with the front diff. This was a loose pinion bearing.

Bad front differentials can also cause significant vibrations within your vehicle. There are also other signs, including your vehicle using more oil than usual or abnormal wear-and-tear on your tires. 

Pro Tip: If something goes wrong while you’re on the road, you’ll want someone to call for help. We uncovered the Best RV Roadside Assistance for Peace of Mind on the Road.

What Happens If a Differential Breaks While Driving?

Generally speaking, you usually won’t encounter a total failure of your front differential in a single moment while driving. Instead, the problem will typically begin as steering issues or noise and gradually increase in intensity. This should give you plenty of time to get off the road to a safe place or a repair shop.

In the rarer cases where your differential just “goes out,” you may experience a loss of power and steering while turning. Your vehicle will then come to a stop and remain unable to drive until repaired. In worst-case scenarios the differential can actually catch fire if it gets too hot. This can cause catastrophic failure and a vehicle fire.

differential fire
It’s rare, but we have seen differential fires in the past. Failing to fix them in time, or letting them run dry on oil can be cautrastoophic. They rarely have sensors that tell you if they are failing so if something feels or sounds off check it out.

Can You Drive With a Bad Front Differential?

As noted above, it’s entirely possible to drive with a slightly damaged front differential. However, you shouldn’t do this except in circumstances where it’s absolutely necessary. While you may retain most of your handling ability, the problem may worsen at any point.

If you believe you’re having front differential issues, you should head to a mechanic or repair shop as soon as possible to have your vehicle examined. 

Mechanic repairing car.
A damaged differential can impact your steering abilities and should be repaired as soon as possible.

Can a Bad Differential Cause Transmission Problems?

It’s somewhat rare, but possible that issues with your differential could cause damage or other problems with your transmission. This is typically when your front differential experiences a significant and immediate failure. That can cause a chain reaction of damage to transmission pieces linked to it.

Driving for an extended period on a failing differential can also gradually damage your transmission. In any case, it’s best to have any potential differential problems addressed immediately to prevent the possibility of more severe and expensive transmission issues. 

Pro Tip: What type of transmission do you have? If you answered manual, it may be time to Say Goodbye to Manual Transmission Trucks. Find out why!

Car pulled over on the side of the road.
If your front differential is failing, pull over and have it repaired as soon as possible to avoid further damage.

Can a Bad Differential Cause Power Loss?

Yes, this can result from a seriously broken or malfunctioning front differential. Once a differential has been damaged or no longer has sufficient fluid and lubrication to operate correctly, it will become increasingly difficult to control. That will eventually lead to loss of operation altogether if a catastrophic failure occurs. However, this is relatively uncommon, as many drivers will opt to repair their vehicle once initial problems become apparent before total failure. 

Mechanic looking at the underside of a damaged vehicle.
Like all car damage, replacing your front differential can get expensive. Shop around for the best price!

How Much Does It Cost to Replace a Front Differential?

Like many auto repairs, your costs can vary greatly depending on the type of place you’re getting your vehicle serviced. In addition, the severity of the damage to your front differential will also dictate the cost of your repairs.

Minor differential issues typically cost between $200 and $400 to repair, while more severe problems can cost twice that much. Significant repairs or replacements of your differential or transmission parts can easily reach $1,000 to $2,000 in some cases.

As always, it’s worthwhile to get several quotes from varying places to ensure you’re not overpaying for service. 

Front Differential Gear Ratios

One thing you will come across when learning about differentials is the gear ratio. This is usually something you do not need to concern with as it’s set from the factory, but if you make modifications it’s critical to understand it.

The gear ratio of the differential is the final gearing change from the transmission to the wheels. A ratio is always a number like 4.33:1 This means that the transmission will turn 4.33 times for each 1 revolution of the tires. A higher number means more torque to the road but higher transmission speeds. The number alone does not mean much however because transmissions have differing final output speeds.

The most critical thing to know about differential gearing is if you choose to change a 4x4 gear ratio. Many times you do this to give the vehicle a better torque ratio with larger tires. Keep in mind that if you change the rear ratio the front needs to change as well. The differentials must match or you will turn the wheels at differing speeds. This will cause excessive tire and drivetrain wear when in 4x4.

differential gear
We changed gear ratios in our truck but only had to do the rear because it is a 2wd. We changed ratios to get a better torque for towing, it however increases engine RPMs and thus we drive slower on the highway.

Your Front Differential Is Crucial

Your front differential is truly the strong, silent type when operating correctly, helping your vehicle handle seamlessly and safely. It’ll typically work seamlessly with just a few humble gears and mechanisms. However, it’s crucial to know the signs of trouble so you can take care of them before minor problems become big ones.

How much do you know about your front differential? Drop your knowledge in the comments!

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Tom & Caitlin Morton of Mortons on the Move gave up the stationary life for one where they are constantly on the move. They are full-time travelers, television hosts, and digital media producers.
They left their jobs, sold their house and possessions, and hit the road in September 2015 in their full-time “home on wheels”. Since then they have traveled the US, Canada, and even internationally by RV.
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