Project DC2 Integra- Getting More Grip With OS Giken and Better Response With Centerforce


Under the cone spring is one of the two clutch packs. Half the clutch packs are tabbed to the differential case, the other half are splined to drive the side gears which are also splined to the axles.

The resistance in movement that the clutches make between the case and the side gears is the lock preventing one wheel from running away and free spinning.


Here is a close look at the clutches. The case driven clutches are tabbed on the outside while the side gear driven clutches are splined to be driven on the inside diameter.

To reduce the total amount of lock, individual clutches can be deactivated by pairing the case clutches or side gear driven clutches. It is pretty rare that you would even want to do this though with an OS Giken diff given the other tuning options.

Note the grooves on the clutch plates. These allow for a good flow of gear oil to keep the plates cool and lubricated. This not only assures for long clutch life but also helps keep clutch chattering and racheting to a minimum. OS Giken diffs are among the smoothest and quietest clutch type LSD differential on the market.


At the center of the OS Giken diff are the pressure rings, spider gears, and cross shafts. They are all contained within this assembly. This is the heart of the diff where a lot of the tuning magic takes place.

A cool thing about the OS Giken diff is that it has 4 spider gears and two cross shafts. Stock differentials typicaly only have one cross shaft and two gears, which tend to break. The OS Giken diff is literally twice as strong in this regard.


The center assembly has two halves. In the center are the cross shafts that the spider gears spin on.

On the ends of the of the cross shafts are cams.  When one wheel starts to spin faster than the other, the side gears put a torque on the spider gears which transfers the torque to the cross shafts. The cross shafts cams then spread the pressure rings apart which puts more clamping force on the clutch packs, increasing the amount of lock that the differential has.

Several factors affect the locking characteristics of the differential. The first is the shape of the windows that the cross shaft cams ride in. If the windows are a symmetrical diamond shape, the locking force is close to equal on acceleration and coast, this is called a 2-way differential. The diff will lock close to equally on acceleration and deceleration. This is great in applications where you want to use the gas or brake to rotate the car, like drifting or rally.

If one pressure ring is like half of a diamond and the other a flatter diamond or even a half circle, the differential is a 1.5-way. This means that the differential locks harder on acceleration than deceleration. The 1.5-way is the best all around for an RWD car, but generally looks up too hard on deceleration and causes understeer on turn in for FWD and the front of AWD cars.

On our diff, the pressure ring windows are diamond shaped on the acceleration side of the cross shaft cam and flat on the deceleration side. This gives a positive lock under power and way less lock on deceleration. This is called a one-way differential. This setup usually works best on an FWD or the front of an AWD car.

The shape of the windows has a lot to do with the locking characteristics. Triangularly shaped ramps on the windows will lock sooner and harder while flatter shaped ramps will lock softer and later.

The next tuning factor is the shape of the cams.  The cams shape affect how the cams will engage with the pressure ring windows and control how much wedging action they will have.  A pointy cam shape will lock harder and sooner while a rounded shape will lock softer and later.

What shape your windows and cams have are determined by OS Giken for your anticipated use. For instance, a drift diff will have diamond-shaped windows and a cam that is pointy on both sides for maximum lock on acceleration and deceleration. An FWD diff like ours will have a window that is diamond shaped on the acceleration side for maximum lock and flat on the deceleration side for minimal lock. The cross shaft cams will be pointy on the acceleration side and flat with rounded corners on the deceleration side for a very slight locking effect.

The final tuning factor for an OS Giken diff is the pressure ring springs. These springs are placed in between the pressure ring halves and counter the wedging action of the cross shaft cams. These control how quickly the locking action comes in. OS Giken has 3 weights of springs from soft to hard. A soft spring allows for faster lock up and is something like you would use in a drift car, while a hard spring causes the lock to come in more gradually like you would in slippery conditions or in a FWD car.



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