The difference with a differential 

Many people focus on power, suspension or tires trying to find that extra bit of time or grip or whatever it is they are looking for. But somehow people overlook the addition of a quality differential. Over the last year this is something that I wished I would have upgraded years ago. When I added my OS Giken front and rear differentials to my STI I didn’t realize the value they would then add without the issues that so many other differentials bring to the table.

Here is a comparison of the OS Giken rear differential vs the stock STI differential. OS Giken will tune the differentials to your liking prior to shipping them to you which is unlike other manufacturers. This really helps quicken the installation process. OS Giken offers a Front and Rear differential set for the STI.

We installed new bearings with the new differential as they had seen many years of track abuse.

But we reused the same ring gear which swaps over quickly.

Now an enormous advantage to the OS Giken is their precision-machines clutch discs. This eliminates the need for a silly figure 8 break in that others require. They also use twice as many clutch discs which basically eliminates the clunkiness of the traditional LSDs. Now this is something that is extremely important if you are someone who drives their car as a daily, yes it still matters on your racecar but obviously a bit less.

I have driven cars with other manufacturers LSDs and it is very obvious that they have an aftermarket unit in the car. Now some of us might love the feeling of our new part but not so much when you try to get into a parking spot and everyone stares at you like your car is falling apart as it clunks and skips the tires. Instead the OS Giken unit give you a very stock like interaction in circumstances such as this. Then you get on track or in any grip desiring situation and you apply the throttle you are given the gift of GRIP!


This is a result of their pressure ring, where springs works in opposition of torque being applied. This then gives you a very smooth activation of grip which is excellent for rolling on power as you come out of a corner. Others tend to instantly and over agressesively push torque to the wheels which can lead to wheel spin when you don’t want it. Keep in mind that the OS Giken can be modified to alter the rate of which it reaches full lock.


The first track that I took the car to after installing the differentials was Willow Springs Big track. Now most associate diffs with better slow speed turning but I was amazed at how the increase in grip at the end of Turn #2. It was quite astonishing how the front diff pulled you around the corner.


At the end of a very hard year of racing the advantages that the OS Giken differentials gave were absolutely something I wouldn’t go without again. I only regret not doing them sooner, then maybe my street class records would be faster! Now the next time you think you need another fancy suspension component or a new turbo maybe think instead about a quality differential as it can be the difference you are looking for in your car!

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