Everything you need to know about Differentials

The most common option is an "Open" differential, which means that though the differential will send power to the wheels it is connected to, the differential itself will not do anything to control or adjust how power is sent to either wheel.

The most common option for the center differential is a "Viscus" differential.  These differentials are sealed, and have plates surrounded by a unique type of fluid that will start to resist the plates moving as it heats up.

Depending on the location of the differential, you will have a couple of different options if you need or want to replace the differential to get the car to handle the way that you want it to.  We have made a number of videos looking at these different options, and when and where you may want one type of differential or another.

Now, all of those videos are collected in one place!

This episode of the Podcast is a little different. 

We have a Modena differential in the shop, and we are going to be taking a close look at it so I put up a picture in our Community section to see what you all would want to know about it.

In response I got a number of great questions about differentials in general.  And rather than answering them each in the comments, I decided to answer them in the form of a Podcast!

The idea here is that this should be more helpful, and make the information easier for others to find and use.

Let me know what you think about this format and if this goes well, I think that this is something that I will try to do more in the future.

Thanks for watching and Stay Tuned!

From 2004 all the way to 2021, the STI had a Driver Controlled Center Differential.  This DCCD sits in between the front and rear differentials, and somehow controls how power is split between the front and rear axles.

If you are doing an STI 6-Speed swap into a WRX or other Subaru, you typically want to install some kind of aftermarket DCCD controller so that you can get the DCCD to work.

But what does the DCCD actually do?  

Does it really change how the power is sent to the front and rear axles?  Can you disconnect the front axles from the car all together if you set it to open?

We got a lot of questions about exactly what a DCCD does after our deep dive into a couple of aftermarket DCCD controllers, so for this video, we want to take a closer look at exactly what the DCCD does.

Very generally speaking, differentials are thought of in two types, open and limited slip.  But if you take a look at limited slip differentials, there are 3 main types  for automotive performance: Viscous differentials, torque biasing or helical differentials, and clutch type limited slip differentials.

Those three types of differentials all behave differently, and have different applications where they are ideal.  Of the three, the clutch type is probably the most complex but it also gives you the greatest ability to tune the way that the differential works.

We have been working with Cusco USA to set up differentials for our cars and our customers cars for years, and they have been a huge help to us.  One of the first thing that we realized was how helpful it is to work with someone that has a lot of experience setting up a differential because of all of the options that you have.

And through the years, we also realized how easy it can be to overlook the set-up options that are available if you do decide to use a clutch type LSD.

For this video, we got a lot of information from Cusco USA, and they even sent us a differential to use so that we could take a look at the inner workings of the differential and how it works.

Thanks for watching and Stay Tuned!

From the factory, the STI comes with a front and rear Gear-Type (Torque Biasing) differential, and these are one of the secrets of why the STI handles so well.

But what if you want to add those differentials to a WRX that didn't get them from the factory?  Or what if you are running past the limits of the Torque Biasing differentials?  

How would you tell and what would you want to replace them with?

When do you actually need a Plated LSD in the front or the rear?

We have talked in the past about how these types of differentials work, but what does it feel like?  

For this video, now that we have a WRX with each type of front and rear differential installed, we are going to try to show you how the work and feel different, and which option would be best for a specific application?

Thanks for watching and Stay Tuned!

For the Pikes Peak Hill Climb this year, we made a number of changes.  One of them was to install a Modena Sequential into our WRX/STI Hill Climb car, but in doing so, we also installed a Modena R180 rear differential.

We have run Cusco differentials in our race cars for years, but given the goals that we had for our run up Pikes Peak this year, we decided that it was time to move to the Modena differential.

There are a couple of key details that set Modena apart from other differential manufacturers, so we wanted to take a look at those differences, and why they allow the Modena differential to work a little differently than the rest.

Tasso from OTC Racing is doing a lot of work on his race car this off-season.  One of his projects is to remove the STI Clutch-Type rear LSD from his R180 rear differential, and replace it with a Cusco LSD.

We have been running a Cusco rear LSD in our Rally car for a number of years, and we have had a few conversations with Cusco about setup options with their rear LSD in that time as well.

So as a starting point, we picked a Cusco 1.5 way rear differential for Tasso's application to go along with his custom Cusco 1-way front differential that Cusco set up for him a little while back.

One of the unique features of the Cusco LSD is that it comes with 2 different sets of ramp angles in it, and in the case of the Cusco R180 Rear LSD, the 1.5-way also comes with the 2-way ramp angles.  We were going to initially make this video about switching Tasso's diff over to the 2-way configuration, but in the process of doing that, and the conversation about the differences between the 1.5-way and 2-way setup, Tasso decided to go back to the 1.5-way configuration.

Fortunately, we happened to capture the majority of that conversation, and we decided to put it up for you here.  If you are wondering which differential you need, or how to set it up, maybe this conversation will help.

In an all wheel drive car, power is sent to all four wheels through your drivetrain.  Because you are sending driving force to all of your wheels, one of the main benefits of an all wheel drivetrain is that the car always feels like it has lots of grip, regardless of the driving surface.

If you have an all wheel drive Subaru like the WRX or STI, your car has 3 differentials that determine how your power is distributed to the wheels.  There is a front differential that determines the split between the front two wheels, a center differential that determines the split between the front and rear axles, and a rear differential that determines the split between the rear wheels.

Even though the drivetrains are nearly the same between the WRX and the STI, but if you drive each of them, they feel different.  The STI feels like it has a lot more grip and like the STI's drivetrain is able to distribute that driving force much more effectively than the WRX.

The reason for this is that the STI has much better differentials than the WRX.

There are a number of up-grade options for your WRX to improve your differentials, and there are options for the STI as well.  

In this video we talk about the difference between gear type or torsen differentials and clutch type differentials (also known as limited slip differentials or LSD's), and where and when you would want to upgrade your stock differentials to improve your drivetrain.

We have been using the MAP DCCD Center Diff Controller in our Race Cars for a number of years now.  This is also one of the best DCCD controllers if you are swapping an STI 6-Speed transmission into your WRX because of the functionality and tunability that it offers.

But we have received a number of questions through the years about how to use the MAP DCCD controller, how to change settings, etc.

So we have put together this video as a guide from the basic use of the controller, up to how to load in different maps, and start making custom maps as well.

Hopefully this helps you get more out of your MAP DCCD controller, and thanks for watching!

Stay Tuned!