Frequently Asked Questions

 What is a differential and what does it do?

Simply explained, a differential is the last point between the engine and the wheels where power is transferred. The differential functions as a system to direct engine power at the wheels while allowing them to rotate at different speeds. There are several types of limited slip differentials (LSD): Open, Viscuous, Torsen, Clutch-type, etc. The OS Giken SUPER LOCK LSD is a unique and patented style of clutch-type LSD which offers many advantages compared to its competitors.

Want to learn more about LSD's and how they work?
Please Check How Differentials work.

 How does a clutch work?

A clutch is a device which connects two spinning devices together, allowing them to lock together and spin at the same speed, or be decoupled and spin at different speeds. In an automotive application a clutch is necessary since the engine constantly spins, but the wheels do not. Friction is necessary to lock the clutch disk to the flywheel, and the higher the output of the engine, the more friction is necessary to effectively transmit power to the drivetrain and eventually the wheels. OS Giken clutch kits are unique in that they are engineered with racing in mind to improve on the existing design in the vehicle, rather than simply replace an existing part with something overly similar. This is the reason that all OS Giken clutch kits include both the clutch disk(s) and flywheel; they are designed and sold as a unit to upgrade the entire system instead of working within the constraints of the OEM design.

Want to learn more about clutches and how they work?
Please Check How Clutches work.

 What is the difference between an OS Giken SUPER LOCK LSD and another companies LSD?

In racing applications, the function of the LSD is to allow the drive wheels to apply equal traction under acceleration and deceleration. Unlike our competitors' products, the OS Giken SUPER LOCK LSD is engineered to be extremely responsive to throttle input to smoothly lock or loosen accordingly. Through its innovative and patented design, up to twice as many friction plates are able to fit into the housing when compared to our competitors' products, enabling the OS Giken SUPER LOCK LSD to achieve true 100% locking capability. Unlike our competitors, the OS Giken SUPER LOCK LSD is also customizable by adjusting the spring inside the pressure ring. Additionally, its superior design allows for excellent streetability, virtually eliminating the “chatter” associated with other clutch type LSD brands. Each component of every OS Giken SUPER LOCK LSD uses only the highest grade materials and manufacturing processes and is constructed and finished to extremely tight tolerances, eliminating any “break-in” period necessary with other brands. Due to its superior design and extreme care throughout the manufacturing process, there has yet to be a case recorded of an OS Giken SUPER LOCK LSD failing in the field, or even requiring a rebuild!

  OS Giken SUPER LOCK LSD advantages :

.:. A true 100% locking LSD: No movement of internal parts means less heat is generated while in operation and less wear of the friction disks. Less initial torque loss and incredible longevity and durability can be realized.

.:. Proven Durability and Reliability: No drop in performance or loss of initial torque, even during long and stressful endurance races.

.:. Straight line stability: During a drag race, our LSD will lock 100% and provide torque equally to each powered wheel. Stable and straight runs will result thus eliminating torque steer in FF applications and lower the chance of drive-shaft breakage.

.:. Customizable: Lock timing can be customized by adjusting the spring inside the pressure ring. Tune the LSD to custom fit any application and set-up of your desired vehicle and driving style/skill level for optimum performance.

.:. By using a pressure control ring, the LSD responds smoothly to the application of initial torque. Lock engagement is smooth and the impact vibration is significantly reduced. This increases the stability of the vehicle and allows more freedom for the driver to trace the desired racing line.

.:. On snow tracks and regions with unstable road conditions, our OS SUPER LOCK LSD easily adapts and adjusts tire rotation to increase vehicle stability. Bad weather and harsh road conditions are not a problem when the vehicle is equipped with an OS SUPER LOCK LSD

.:. Less under-steer during cornering: When entering into a corner with the throttle closed, the spring inside the pressure control ring will react accordingly and immediately return the differential's internal components to the original initial torque settings and thus creating less under-steer. However, with a conventional differential, there will be a lapse of time before returning to the initial torque settings, as it takes time for the cone springs to react and make contact with the friction disk in order to close the pressure ring.

.:. When exiting from a corner, our LSD's transition to the full 100% lock position is smooth and predictable. This gives the vehicle better traction and stability, resulting in better lap times while racing.

.:. OS Giken SUPER LOCK LSDs do not require any break-in process. OS SUPER LOCK LSD's are composed of parts that have been precisely machined to exact specifications and are ready to use upon installation.

  What is the difference between an OS Giken clutch and another companies clutch?

OS Giken originally started in 1973 as a race engine builder for Nissan, and gained notoriety for its legendary TC-16 motor (based on the Nissan L-Type). However, at that time the motor that OS Giken developed produced more power than any Nissan clutch could handle, and it was at that time that OS Giken decided to develop their own clutch to satisfy the power transmission demands in their racing applications. Through years of development and since its first introduction to the public in 1983, OS Giken clutches have always focused on extraordinary durability, drivability, and effective power transmission. In order to properly develop a clutch system to maximize drivetrain performance, OS Giken determined that it would be most effective to engineer and manufacture clutch kits as a clutch/flywheel package. By doing so, a clutch kit can be installed which has already been properly matched to any specific application. Additionally, the design, engineering and manufacturing of OS Giken clutch kits promote improved durability (through friction plate material which is carefully selected and alloyed so that the plates match with the materials of the flywheel and center plate), maintained drivability (through revised leverage mechanisms to provide higher disk pressure while reducing pedal effort), increased longevity (through a superior design and usage of extra manufacturing processes for strengthening)

 How much torque does an OS Giken clutch hold?

When it comes to measuring torque, there are two main methods: static and dynamic. Basically, a dynamic measurement involves acceleration while a static measurement does not. Many competitors list a torque capacity for their clutch lineup, but the actual torque capacity will depend on a variety of factors such as vehicle weight, tire traction, etc. Furthermore, it is unclear as to whether the torque capacity listed by our competitors is static or dynamic, and if it is a dynamic measurement, it is unclear as to what factors are included with the measurement. The simplest way to physically measure torque capacity of a clutch is to mount a clutch to the crank, attach a torque measuring device, and take a measurement at the point that the clutch begins to slip. However, this method does not take other important vehicle factors into consideration (weight, tires, etc.)
There is also a formula for static torque capacity measurement:

  T=NxRxFxP (Torque capacity=Number of friction surfaces x Radius of gyration x coefficient of Friction x Pressure plate clamp force)

Using this formula, the range of static torque capacity would be about 610 ft lbs.f for our Super Single, up to about 2149 ft lbs.f for our R4C quad plate! Obviously, these numbers are not applicable to the real world since vehicle information is not factored in.
Since it is unrealistic to provide a solid torque capacity number without knowing all the specific details, we have chosen to recommend an OS clutch based on the power output and driving types of our customers (street, road race, rally, drag, etc.). Please contact your authorized OS Giken dealer with your inquiries!

Want to learn more about torque measurement methods?
Take a look here: torque-measurement.pdf

 Why are OS Giken products more costly when compared to other companies with similar products?

Since the company's inception in 1973, OS Giken engineers, develops, tests, and manufactures its products within these criteria:
.:. Excellent durability
.:. Superior performance
.:. Competitive edge
.:. Highest possible reliability

Some competitors offer their aftermarket performance parts as a supplement to their OEM parts distribution; conversely, OS Giken builds engine and drivetrain components specifically for racing / high-performance use, to give its customers every available advantage in competition. Only the best suitable materials and manufacturing processes are utilized, including costly procedures such as raw forging, heat treating, dual-sided simultaneous disk finishing, etc. Often, OS Giken parts are so well engineered and manufactured that the parts outlast the life of the vehicle. OS Giken strongly believes the old racers' adage “In order to finish first, you must first finish.” Although the initial cost of an OS product may be significantly more than a similar competitors' offering, OS Giken believes that the added reliability, excellent durability, and superior performance of its products more than compensates for the higher cost, and can actually aid in reducing long-term operating costs in both time and money. OS Giken parts are considered to be in the upper echelon of race-use drivetrain products, are highly specialized, and are therefore not meant for everyone. However, users of OS Giken product are generally very satisfied with their purchase and believe in the saying “If you buy cheap, you buy twice.”

 Why do I need a movement alteration kit for my OS Giken clutch?

All OS Giken clutches utilize the “push-type” diaphragm design; where the cover is operated in a forward pushing motion towards the flywheel in order to disengage the clutch disks. Some vehicle's use a “pull-type” diaphragm design; where the cover is operated in a rearward pulling motion away from the flywheel in order to disengage the clutch disks. OS feels that the inherent design of a push-type clutch is more reliable and less prone to failure when compared to the pull-type design. Additionally, service done to a pull-type clutch is generally more labor intensive than a push-type design. For certain vehicles that are equipped with a pull-type design from the manufacturer, OS has developed a vehicle specific pull-to-push type conversion kit, which will allow the use of the superior push-type design.

 Why do all the OS Giken clutches come with a flywheel?

All OS clutch kits are sold as a clutch / flywheel package. As the designers' and engineers' goal is to develop the best performing and most durable applications available, it is best to circumvent as many limitations as possible that the OEM clutch / flywheel have, by “starting from scratch”. OS clutches and flywheels are properly matched to each other and manufactured with the most suitable materials / designs, in order to maximize durability, drivability, and performance. In addition, by designing the clutch/flywheel package from the ground up, many more options become available for disk size, flywheel weight, etc.

 Why do all OS Giken clutches make a noise when the clutch is disengaged?

All OS clutch kits utilize a free-floating pressure plate design. Most “traditional” clutch designs secure the pressure plate to the cover through the use of a pressure plate drive strap (aka “granny strap”). The advantage of having the granny strap is that clutch operation remains noiseless whether the clutch is engaged or disengaged. However, in many situations where the clutch is being abused (i.e. “spirited” driving and/or racing), the granny strap can become a weak point in the system and has a tendency to bend or break, potentially causing clutch failure and damage to drivetrain components. With the OS free-floating pressure plate design, pressure applied to the disks is even throughout the clutch lifespan, and the friction material of the metallic disks is bonded through a specialized process (as opposed to the cheaper riveted process used by most other competitors and OEM). This aids in increasing durability and lengthening the useful service life of an OS clutch, as power will continue to be transmitted effectively until the disks are extremely thin (since no rivets are present to create another weak point). Some race teams have gone through multiple seasons on an OS clutch before requiring a rebuild!

In regards to multi-plate clutch designs, all aftermarket manufacturers' multi-plate clutches will inherently emit a noise when the clutch is disengaged. This noise is emitted from the centerplate(s) vibrating against the cover posts. However, many competitors' clutches do not utilize the same strengthening processes during manufacturing as OS Giken, which will lead to increased material degradation over time. Because of this, the clutch noise will often become louder over time, as the centerplate(s) start to wear away and have more free-play within the housing. The OS design, coupled with the use of the most suitable materials and manufacturing processes, will minimize any system degradation and help to keep the clutch performing and sounding the same as when it was first installed. In fact, many OS Giken clutch users are proud to point out the signature noise emitted to anyone who asks, as it is a reminder that the car is equipped with one of the best performing and longest lasting clutches available!

 Some companies outside of the US/Canada/Latin America/Caribbean are selling OS Giken products in this market, why not just purchase from them?

Any retailer that is not authorized to distribute OS Giken products in the United States/Canada/Latin America/Caribbean is doing so as a grey market item. Toyota Tsusho America, Inc. is the exclusive distributor for OS Giken in these territories. Any OS Giken product sold in these territories through distribution channels outside of Toyota Tsusho's approved distributor network does not qualify for any warranty or technical support. Toyota Tsusho America has gone to great lengths to market and distribute OS Giken product here, and makes every effort to maintain local inventory, support local businesses, manage local marketing, and deliver product as quickly as possible. Purchasing OS Giken product through grey market channels only serves to hinder the local economy and puts the end user into a situation where no support can be offered should the need arise. More often than not, purchasing grey market products results in extra long lead times, with no guarantee that the correct product will be delivered, and no local technical support should an order arrive with missing or incorrect parts, etc. Additionally, extra fees hidden in shipping/duties charges often make purchasing through the grey market more costly than purchasing through an authorized agent. We strongly advise to confirm that your OS Giken retailer is a part of the authorized distribution network before placing an order.