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If two wheels are locked on an axle so that they aren’t free to turn separately, one or the other wheel will slide. So, engineers had to find a way to connect both rear wheels to the engine without the applications slipping or sliding when you drive around corners.
The device that makes this possible is part of the rear axle and it’s called the differential because it can drive the rear wheels at different speeds. The idea of a differential is to allow two wheels to turn at different speeds while going in the same direction. So, when you’re turning a corner the outside wheel will turn faster than the inside wheel in order for the car not to slip on the road.
To find out more about differentials, here is a complete guide on what type of applications there are inside modern cars and what products you need to maintain them.
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What is a Limited Slip Differential?
If one of the rear wheels of your car loses traction the torque goes to the path of least resistance and spins the wheel that has the least grip. The wheel that does have grip will receive less power which isn’t ideal for the application to operate, so that’s where a limited slip differential comes in.
The limited slip differential limits works by sending power to the opposite wheel or axle with the best grip. Typically front-wheel drives have this same function but the limited slip differential is built into their transaxle which is located in the front of the vehicle.
Take a look at the following types of limited slip differentials:
- Geared limited differential: This application uses spring loading and a pack of gears that are standard or open differentials.
- Clutch or plate limited differential: It uses a clutch or plate to engage one output shaft or the other based on wheel resistance. If a wheel spins, its clutch or pressure plates loosen to send it less torque.
- Viscous coupling limited differentials: This application has discs spinning inside a cylinder filled with silicone fluid.
- Electronically limited differential: It’s controlled by the car’s computer. It reads wheel slip and subsequently commands clutches electronically to tighten or ease up the engagement on one wheel or the other.
With these four limited slip differential methods, there are other applications that can detect torque or wheel speed to make the decision of which wheel speed to alter.
So now you know that when your car has a limited slip differential it’s got a technology that’s built into the wheel’s axle that detects when a wheel has lost traction. Then it can send more torque to the application that allows you to drive smoothly around corners.
A limited slip differential optimizes your car’s performance, traction and safety.
Limited Slip vs. Open Differential
The open or standard differential has an integrated component connecting the wheel axles that have turning mechanisms inside called spider gears. These spider gears allow the wheels to work at different speeds so that they don’t lock when you’re turning a corner. Open differentials are built into most standard vehicles and they are lightweight & easy to maintain.
One of the drawbacks of an open differential is that if you get stuck in a mud pit and one wheel is slipping, the wheel that has the least resistance will receive all the torque from the engine. This will result in the wheel spinning and digging deeper into the mud because the open differential will always go to the path of least resistance.
Limited Slip Differential
The limited slip differential works in the same way of an open differential when your car is driving in consistent motion. It will send power to both wheels when they’re rotating together. But when a limited slip differential detects that a wheel is slipping it will automatically transfer more torque to the wheel that has more traction.
It works by a combination of clutches and springs that sends torque to the tire that grips which allows you to make sharp turns and drive through mud pits easily. A limited slip differential is typically found on performance cars to improve handling and grip. It’s also found in trucks and SUVs to optimize traction on slippery roads or rocky terrain.
What does a Limited Slip Look Like?
We mentioned the four main types of slip differentials but what do they look like? To help you identify what type of limited slip differential you have in your vehicle, our next section will give you a short breakdown of what each of these applications looks like.
Clutch Limited Differential
Construction of the clutch limited differential includes the following:
- A ring gear
- Pinion gear
- Side gears
The clutch pack based limited differential has a series of friction and steel plates located between the side gear & casing. Friction discs are locked with the side gear which will always move together. The steel plates have protruding tabs that fit perfectly in the case’s grooves.
These steel plates are locked inside the casing so they can move together as one unit. The clutch pack assembly is well packed so the motion from the casing is directly passed through to the corresponding axle. The space between the side gears is fitted with a pre-load spring which will give a thrust force that presses the clutch pack together.
Geared Limited Differential
The geared limited slip differential uses worm and spur gears to transfer input power between two wheels. Worm gears are meshed with each half of an axle. The spur gears are located at the end of each pair of worm gears to connect them. It’s the connection of the worm gears that transfers power from one wheel to the other when an axle begins rotating faster than the other.
Viscous Coupling Limited Differential
The viscous coupling limited differential relies on hydrodynamic friction from high viscosity liquids instead of clutches and gears to operate the axle. This application has fewer moving parts and is less complex than mechanical limited differentials.
A viscous coupling limited differential is a cylindrical chamber that’s filled with silicone-based oil. Inside the mechanism you’ll find perforated discs that rotate with the motion of the output shaft. The inside chamber is connected to a driveshaft and the outside is attached to the differential carrier.
Half of the discs are on the inside and the other half of the discs are located on the outside of the chamber. The motion of the differential forces the discs to move against each other through the liquid inside the chamber.
Electronic Limited Differential
The electronic slip differential has bevel or planetary gears similar to the clutch pack application. The only difference is that these gears are operated externally by the vehicle’s computer system. Electronic differentials use the steering wheel commands and speed signals to control the power from one wheel to the other.
What Type of Gear Oil Should you Use?
- Formulated to maintain excellent low temperature fluid protection
- Helps provide outstanding thermal stability for cleanliness and longer service life
- Popular for cars and light trucks like Ford Mustang, Ford F-150, Dodge Ram, Toyota Tundra and Sequoia, and Jeep Cherokee
- Contains additional friction modifiers for suitability with clutch-type limited slip differentials for most LSDs
- Klotz FREE-GEAR Estorlin Synthetic Hypoid Gear Lubricants provide extra protection needed to improve speed and acceleration, while still withstanding the extreme shock load applied to differential gears in racing
- After years of testing with top race teams in the nations premier racing series, FREE-GEAR Estorlin is one of many lubricants Klotz offers to improve driveline performance
There are various types of gear oil on the market for your vehicle but how do you know which one is suitable for your car? Firstly, consider what type of vehicle you’re driving and the climate you live in. If you have a heavy-duty vehicle you’ll need to purchase oil that has a higher grade viscosity. You can determine the viscosity of the oil by the load and speed of your vehicle as well as the temperatures you live in.
For example, oil with a grade of 75W-90 is defined like this: 75 refers to cold weather viscosity oils. The lower this number is, the less viscous the oil will be in colder weather. The ‘W’ stands for winter and the number after this letter refers to higher temperatures. The higher this number is, the thicker the oil will be in hotter climates. The 75W-90 differential oil works for both heavy and light-duty vehicles.
Another aspect you should consider when purchasing gear oil is what types of additives are inside the liquid. There are three types of additives:
- Rust and oxidization: This additive provides protection against corrosion and secures chemical stability.
- Anti scuff: Provides a stronger film inside the application for added protection against damage.
- Compound: Oils with compounds have synthetic fatty acids that increase durability and lubricate the application effectively. You can get mineral or synthetic compounds. The mineral-based oil has more pressure viscosity compared to synthetic liquids. But synthetic compounds provide better protection against corrosion and thermal degradation which makes this oil ideal for high operating temperatures.
What does Differential Fluids Do?
Differential fluid lubricates the pinion and ring gears that transfer power from the driveshaft to the wheel axle. It keeps all the mechanisms inside the differential cylinder in a healthy working condition.
The purpose of differential fluid is to decrease friction and effectively lubricate the moving parts inside the differential such as the bearings & clutch packs.
What Happens if you Don’t Maintain Your Differential?
If you don’t change your differential fluid at the intervals stated in your owner’s manual the gears inside the application could wear which produces grinding noises. Over time your differential will fail and this can be a safety hazard as it will cause your gears to seize and your rear wheels will lock up. You won’t be able to turn your wheels and this can cause an accident due to loss of wheel control.
On most standard vehicles the differential fluid should be changed every 30,000 to 50,000 miles. For heavy-duty vehicles, the fluid should be changed every 15,000 to 20,000 miles. As mentioned before, if you’re unsure when you should change your differential oil, simply refer to your owner’s manual.
Differential Fluid vs. Transmission Fluid
Transmission fluid, also known as ATF, is not the same as differential fluid. The formula for transmission fluid is filled with lubricants that keep your transmissions running smoothly to decrease internal vehicle wear. It also works as a hydraulic fluid for power steering.
With lubricants, the transmission fluid also contains additives such as the following
- Surfactants that clean the metal components inside your vehicle’s transmissions
- Seal swell
- Cold flow optimization
- High-temperature thickeners
Transmission oil is red or green in color and it’s thinner than differential oil. The differential oil (gear fluid) is used to reduce friction when you change gears using your clutch. It contains sulfur-bearing anti-wear compounds and it’s thicker than transmission oil because it’s used to lubricate the gearbox & differentials.
It’s important to know the difference between the two oils. This is because transmission fluid doesn’t have the thickness needed to lubricate a gearbox or differentials and gear fluid doesn’t contain the additives to maintain a transmission system.
What Happens when a Rear Differential Goes out While Driving?
There are noticeable symptoms of a rear differential that’s in poor condition. The first major sign of a damaged differential is difficulty in vehicle handling. As mentioned before the differential is responsible for optimizing wheel turns around corners. When your differential starts to wear the wheels won’t be able to adjust speeds which will decrease your car’s handling ability.
You may also notice significant noises such as squeaking or grinding sounds. These sounds are caused by a lack of lubrication of the internal mechanisms inside your differentials. If your rear differential goes out while you’re driving you may experience a skip in power or vibration that may increase as you accelerate.
This is caused by broken or worn out teeth on the differential gears. The more gear teeth that are worn or damaged the more severe the noises, vibrations and skip in power will be. This could result in loss of complete control or power over your steering and your car could cut out.
How to Determine which Differential Your Car Has
The easiest way to determine what type of differential your car has is to check the bolt count on the application’s cover. Most differentials have their own unique set of bolt counts. You can get a 10, 12 and 14 bolt cover which will help you identify the differential your car has. Another feature to look for is if your differential has an integrated housing or a drop out application which doesn’t have an inspection cover.
You can also look at the type of axle shaft you have: either a semi-float or a full-float application. These two axle shafts can either be a bolt-in or C-clip application which is how the axles are fitted onto your vehicle.
Other ways to determine the type of differential you have is the following:
- Pinion size
- Diameter of the ring gear
- Bolt pattern on your wheel hubs
- Pinion support
- Length of your axle shaft
What does Limited Slip Additives do? (Red Line 80301 Limited Slip Friction Modifier – 4 oz.)
- Replaces the limited-slip additives
- Can be added to any gear oil
Inside the differential, there are many mechanisms made from various types of material such as metal, paper, sintered bronze and carbon. Each of these materials have different frictional and wear characteristics that require an additive to maintain the durability of these mechanisms.
The most essential component inside premium differential oil is limited slip friction modifier. It decreases the friction of the mechanisms inside the differential to minimize the wear of the gears and to prevent oxidization. Friction modifier additives eliminate noise, stick-slip issues and vibrations by lubricating all the components needed to optimize your vehicle’s performance.
This additive can be found in the Red Line differential fluid. It’s designed to maintain differentials inside performance and standard vehicles. The Red Line offers excellent lubrication under extreme conditions.
The Red Line differential fluid has a high viscosity index so it will have a consistent thickness in all weather conditions. It lowers operating temperatures by reducing sliding friction in hypoid gears. Compared to other synthetic gear oils the Red Line 80301 differential fluid reduces oxidization and exceeds API GL5 specifications.
This product lasts longer than other synthetic differential fluid which means it extends draining intervals. The thickness of the oil is known to boost fuel economy and decrease gear wear. One advantage of the Red Line 80301 differential fluid is that it’s OEM (Original Equipment Manufactured) oil which means it has the correct amount of lubricant additive to reduce gear chattering.
As you can see the slip differential inside your vehicle plays an important role in how your car operates. That’s why it’s essential that you maintain your differential according to your owner’s manual.
If you suspect that your differential is not operating at its full potential take it to your nearest mechanic for check ups. It’s easy to change differential fluid yourself but mechanics can do a faster more secure job of maintaining the application.
Now that you know what this important car part does and how to maintain it you can optimize the performance of your car and ensure that your differential is well lubricated & clean at all times.
Last update on 2020-04-04 / Affiliate links / Images from Amazon Product Advertising API