Apr 042014

In response to racer feedback and OS Giken’s own observations of tuning trends, OS Giken has proudly released the OS Super Lock LSD for the Ford 8.8” (FD881-HA) Independent Rear Suspension differential. OS Giken found that it was becoming common to use the Ford 8.8” IRS carrier for high powered builds for many import sport compacts, due to the 8.8” large sized ring gear, low costs/high availability, and wide selection of available gear ratios. The OS Giken Super Lock is available for both 31 and 28 tooth spline axles. Both designs feature 20 active clutch plates.


All of OS Giken’s Super Lock differentials feature forged cases that are chemically heat treated, providing the highest level of durability and strength possible. Additionally, all Super Lock LSDs are fully tunable for any specific application. Please feel free to inquire with details regarding your unique needs and the engineers of OS Giken will be happy to provide a recommending setting!

Contact UNITRAX for more information on the FD881-HA OS Giken Super Lock.

Jan 062012

The engineers at OS Giken have been very hard at work to bring an outstanding limited-slip differential to market.

The patented design is a revolutionary breakthrough in clutch type limited slip differential design and allows the Super Lock to have up to twice the friction plates compared to conventional designs. OS Giken’s quality craftsmanship and original design enables 100% full locking as well as unparalleled durability.

Corvette C6 1

Some of the unique features of the Super Lock are:

  1. Billeted and Heat-treated case (not found on most competitors’ units)
  2. Forged internals, and RAW-forged gear teeth (strongest gears available anywhere)
  3. More disks+larger disks = more friction surface area to dissipate heat and allow true 100% locking capability. OS units typically house TWICE as many disks as competitors units (up to 28+ plates) 
  4. Ultra-precise disk machining, which means the unit is ready to perform immediately after installation… NO BREAK-IN PERIOD REQUIRED!
  5. Non-intrusive cone spring design prevents unnecessary wear and results in consistent and reliable performance over the long-term.
  6. 100% locking and unlocking capability: True 100% lock results in no moving components results in no heat generation. The main reason other limited-slips fail is because too much heat is generated, since true 100% lock cannot be achieved. OS has yet to see one of their Super-Lock LSD’s fail in the field!

Viper LSD 1

In a recent press release from the OS Giken team,it was stated that “since released to the public in 2000, there have been ZERO failures of a production unit, and ZERO rebuilds necessary at any level, from street use to professional racing.”

Corvette C4

UNITRAX has been trained on how to tune the Super Lock to meet specific requirements. The unit that we trained on, we thought, was a new unit. However, the tech from OS Giken informed us that the Super Lock was removed from a car that competed in three full race seasons!

Recent additions to the Super Lock line are the C4 through C6 Corvette, all model years of the Dodge Viper, Camaro SS, FJ Cruiser, Chrysler, Dodge and Mercedes M215 differentials, BMW, Alpha Romeo, Porsche, and Mini. There are several new applications to be announced soon.

The Super Lock also fits most popular Toyota, Lexus, Nissan, Honda and Mazda differentials.

UNITRAX is excited to be able to offer such a well designed and executed LSD to the drivetrain performance community.

                   Viper LSD 2

Visit the OS Giken site at www.osgiken.net for more information on the Super Lock and the other outstanding product offerings including Clutches, Close Gear Ratio kits, Tranmissions and Engine upgrades.

Feb 022011

Four Limited-Slip Differentials For The Viper SRT 10 Positraction For Street, Strip and Track

The ‘Gen III” Dodge Viper SRT 10 was introduced in 2003 with fresher look, more power, and a new version of the Dana’s resilient 44ICA differential, the M44-4. Along with a new housing, the M44-4 was fitted with Dana’s Hydra-Lok limited-slip differential.

Because the 2003 M44-4 housing was designed to accept the Dana Spicer Hydra-Lok, the Viper community was initially left with no positraction alternatives. However, today the SRT 10 owner has four limited-slip differentials to chose from. Two of the units are engineered to meet the most demanding performance applications and a third is found in the 2008 through 2010 “Gen IV”  Super 44-4ICA Viper SRT 10.

Dana Spicer Hydra-Lok

Dana’s Hydra-Lok was originally developed by ASHA Corporation in Santa Barbara, California. McLaren Performance acquired ASHA and sold the rights of ASHA’s Gerodisc technology to Dana’s Spicer light duty axle division. Dana completed development of the unit and trademarked the LSD as the Hydra-Lok. Production began in Syracuse Indiana and in 1999, Jeep debuted the Hydra-Lok in the Grand Cherokee.

Gerodisc technology is speed and torque sensitive, operates full-time, and offers proportional torque transfer with progressive action. It uses the differential oil to operate the Gerotor. TwinDiscs provide one coupling per wheel. The fluid is released at calibrated pressures to engage the clutch pack.

The Hydra-Lok transfers wheel torque as conditions demand, ensuring improved traction and handling. Unlike traditional disc-based LSD’s, the Hydra-Lok offers controlled torque transfer. It does not waste power on wheel spin, rather it transfers torque to the wheel with the most traction. The torque is independent of the slipping wheel condition. The Hydra-Lok is speed-sensing meaning that the torque transfer is independent of the slipping wheel’s traction. The amount of torque transferred to the wheel with traction is based on the speed of the spinning wheel. Resulting in nearly immediate transfer of torque from the wheels that slip to those that grip.

According to Dana Corporation, when a Hydra-Lok equipped Viper begins to negotiate a curve, the vehicle reacts as if it had an open differential to reduce the potential of over-steer. As the vehicle continues through the corner, it takes on the characteristics of a limited-slip differential, transferring torque to the wheel with traction. Coming out of the curve, however, the Hydra-Lok allows the Viper to deliver the maximum amount of torque to the ground for improved speed while exiting.

The 2003 version of the Hydra-Lok had an issue with cross pins failures. UNITRAX developed a replacement 300m cross pin to help prevent Hydra-Lok failures. In 2004, Dana upgraded the Hydra-Lok with a heat-treated cross pin. However, side gear and pinion gear failures have continued to plague Gen III SRT 10 owners.

Unfortunately, dependability and durability issues have spoiled the promise of the M44-4 Hydra-Lok. We will now examine the alternatives to the Hydra-Lok.

Quaife ATB Differential

R.T. Quaife Engineering Ltd was the first manufacturer to supply a replacement limited slip differenital for the stock SRT 10 Hydra-Lok. The Quaife ATB (Automatic Torque Biasing) Helical LSD differential was originally developed in the 1980s and is used throughout world. While more widely designed and developed for front-wheel drive vehicles, Quaife Engineereing states the traction benefits offered by the ATB Helical LSD differential can also be utilized in rear-wheel drive vehicles.

The Quaife is an automatic torque biasing helical-gear based differential. Unlike a conventional plate-style limited slip unit, the Quaife ATB relies on sets of floating helical gear pinions that run in pockets and mesh to provide the normal speed differential action. Should one of the driven wheels start to spin however, the helical gears start to generate a torque bias thanks to the axial and radial thrust of the helical gear pinions in their pockets.  The result is that there is a progressive transfer of torque away from the spinning wheel of the axle to the driven wheel, which is now capable of transmitting a greater proportion of torque to a constantly varying degree.. The transition of power is smooth and constant without ever completely removing power from the other wheel. The effect is progressive but at no stage does the Quaife ATB lock solid. By getting the power to the ground, the Quaife enables the Viper to accelerate quicker and corner faster.

In cornering, while accelerating out of a turn, the Quaife ATB biases greater power to the outside wheel, reducing inside-wheel spin. This allows you to begin accelerating earlier, exiting the corner at a higher speed. The Quaife ATB provides straight-line acceleration that is close to an an ideal 50/50 power split to both drive wheels when traction conditions are ideal. The Quaife ATB also controls loss of traction when the drive wheels are on slippery surfaces by providing the appropriate biased traction needed to overcome these adverse conditions.

The Quaife ATB powers both drive wheels under nearly all conditions. The differential senses which wheel has the better grip and automatically biases the power to that wheel. However, it must be noted that if one wheel is in the air or on a surface without traction, neither wheel will be driven during that moment in time.

To install a Quaife ATB into the SRT 10 Super 44-3ICA differential, the stock output shafts must be shortened and bore-drilled to accept the anchor bolts.

To maximize the performance of the Viper equipped with Quaife ATB differential, the suspension should be set up like an open differential; stiff springs and a soft sway bar.

The Quaife’s distinctive design offers controllable traction, improves handling and steering, and applies the power where it is needed most. The Quaife ATB is exceptionally strong and generally requires no maintenance.

All authorized Quaife ATB Helical SRT 10 differentials come with a limited  lifetime warranty.

GKN Visco-Lok

The 2008 through 2010  “Gen IV” Viper SRT 10 is equipped with the GKN Visco-Lok. The Visco-Lok has been in production since 1999 and is a standard feature in the BMW M3.

The Visco-Lok is a unique hermetically sealed speed-sensing limited-slip differential. The unit benefits through its high-torque progressive locking characteristics which provides maximum torque transfer in excess of skid torque.

The Visco-Lok operates through a self-contained silicone-fluid filled reservoir and shear pump that actuates a wet friction clutch pack. The pump generates pressure proportional to the speed difference between the wheels. The clutch pack actuates thereby transmitting torque to the appropriate wheel. The locking effect increases with the speed difference across the drive wheels.

This locking characteristic enables the Viper to accelerate well on surfaces with different friction conditions between the drive wheels. Additionally, GKN states that the Visco-Lok allows even better acceleration and less under-steer in cornering than compared to torque-sensing LSDs.

UNITRAX has installed many Visco-Lok LSD’s in Gen III SRT 10 Vipers, giving the SRT owner improved limited-slip performance and in our opinion a substantial upgrade over the Dana Spicer Hydra-Lok. The Visco-Loks have proven to be especially reliable in stock or modestly upgraded Vipers.

OS Giken Super Lock LSD

Starting with a blank slate, the talented engineer, Takuya Tomimatsu of OS Giken Co. Ltd. of Japan has designed the premier Dodge Viper SRT 10 LSD. Using the foundation of 4 years of initial Super Lock development and the world as a proving ground, OS Giken offers their highly respected and race proven OS Super Lock LSD for the SRT 10.

The OS Giken Super Lock LSD is more closely related to the disc-based TracLok LSD found in the Dodge Viper from 1992 through 2002. However, that is where the comparison ends. The revolutionary Super Lock is a true 100% locking LSD that instantly reacts and transitions smoothly from both free and locked positions, combining open differential drivability and limited slip differential performance and stability.

The OS Giken Super Lock features innovative technologies like the adjustable lock timing adjuster. Lock timing can be adjusted by replacing the springs in the pressure ring. Initial torque settings also adjustable through cone springs located at ends of clutch stacks. This allows the Super Lock to be tuned to meet your exact needs for optimum performance. UNITRAX is an authorized tune center and can discuss custom tuning to meet a driver’s specific requirements.

OS Giken is committed to producing an extreme quality LSD. Every Super Lock is manufactured from only the finest materials, regardless of the production cost. The Super Lock housing is manufactured from a proprietary billet steel alloy which is then heat-treated when finished. The side gears and pinion gears are hot forged and hand-finished. This attention to detail improves the precision and performance of the product.

U.S. patented bevel gear-in-pressure ring mechanism has enabled OS Giken engineers to miniaturize each gear, thus providing more space for up to an unprecedented number (28) of all-steel friction plates. The Increased number of friction plates improves the locking force of the LSD enabling it to lock fully and completely. An added benefit to being a fully locking mechanism is that less heat is generated, thus resulting in incredibly higher durability and reliability in even in the toughest racing environments.

OS Giken states that they have tested the Super Lock for over 22,000 performance miles and upon inspection of the unit, there was no wear, no loss of initial torque, and no loss of performance. UNITRAX inspected a Super Lock that was run for three full race seasons. The Super Lock showed no signs of wear and many of the components looked as if they had just come out of production.

The higher locking force provides outstanding straight-line stability at the drag strip. The Super Lock will lock to 100% and transfer torque equally to each wheel.

You will experience less under-steer during cornering. When entering a corner with the throttle closed, the spring inside the pressure control ring will react accordingly and immediately return the Super Lock to its original torque settings. When exiting a corner, the Super Lock’s transition to the 100% locked position is smooth and predictable, resulting in better traction, stability and quicker exit speeds. Additionally, racers and techs have reported that the Super Lock operates significantly cooler then competing LSD units.

One key feature separating the Super Lock from our other clutch type LSD’s is that with the Spec-S (standard) settings, the Super Lock is actually able to function as a open differential at low speed/low torque situations. Thus, when performing a normal slow speed turn (such as a right hand turn on the street) or backing out of a parking space, our differential functions as a normal open differential, allowing smooth turning without premature wheel lock. Of course with performance settings, such as drift which would require a much higher setting of initial torque, some premature locking may occur.

Unlike the Quaife ATB, the Super Lock does not require that the output shafts be drilled and modified. OS Giken engineered the unit to be center-weighted and the Super Lock ships with equal-length 41 spline performance output shafts! Due to the nature of the Super Lock design, featuring 28 all-steel friction plates, the driver may occasionally experience some disc chatter. To temper this characteristic, we recommended the use of O.S. Giken’s OS-250R 80w250 GL-5 synthetic lubricant. The disc chatter in no way affects the performance or durability of the Super Lock. Since the Super Lock runs cool and there are no contaminants from friction material polluting the lubricant, differential oil change intervals can be extended.

The Super Lock is used competitively in the U.S.A., Europe, U.A.E., Japan, Greece, and Australia. It also has a large and growing following in Autocross and Drifting circuits.

To date, there has not been one reported failure of the OS Giken Super Lock in any application. The engineers at OS Giken take extreme pride knowing that the owner of their LSD units compete with the utmost confidence.

The OS Giken Super Lock meets the needs of the most demanding driver who is comfortable with the way his SRT 10 feels with the stock Hydra-Lok or Visco-Lok but wants the tuneability, dependability, and durability that a fully race-engineered and manufactured LSD offers. The Super Lock is quickly becoming the preferred choice in the high-performance community.

If you have any questions regarding limited-slip SRT 10 differentials, please contact UNITRAX at 800.622.4327.


Copyright © 2011 by UNITRAX Drivetrain, Inc., all rights reserved.

Aug 252009

The following (below the posts) is a response from O.S. Giken regarding the Super Lock that generated from the Viper Club forums:


Thank you for letting us know about some confusion arising on the internet regarding our OS Super Lock LSD for the Gen 3 Viper.

I will try to provide an explanation to the following postings that contain some comments that may be misleading when applied to

the OS unit:

The Posts:

Quote #1

I am sure they are a fantastic piece of gear, the stuff they make for Skylines is impressive too.

However to throw out a quaife for one on a street car or a road race car I would question – unless you want to drift.

The fundamental difference is that the quaife is not a true LSD – it applies power to both wheels in a straight line, but to the side that needs it most when traction is lost. It is this function that enables more power out of turns because it is applying more power to the OUTSIDE wheel which means to you get power down and can steer the car.

By comparison, once traction is lost with a locked diff (OS Giken under power) you cannot steer a locked diff car on steering wheel input alone eg. out of a corner or when the back flicks out! You have to steer LSD cars with the throttle as well once they lose traction. This is perfect for drifting, great for drag racing (until the car goes sideways) but terribly unsafe on public roads unless you have the feel and skill to match.

For super high powered cars I would be keeping the quaife – much safer – but then I’m past needing to powerslide at 125mph steering on the throttle yelling “yee haa yahoo!”

Still, for LSD applications – I’d bet this OS Giken will be better than anything else.

Quote #2

Originally Posted by gb66gth

In reading the devolpment info, provided earlier in the thread, something was mentioned about how the OS Giken dif. would reduce understeer on entry into slow corners on a road course (not a direct quote). Can someone explain to me how this works, that is the dif having an efffect on the front end of the car? I’m no mechanical engineer so a little help here, please….

Reduced corner entry understeer is not a characteristic of clutch-type limited slip differentials vs. the stock Viper units or a Quaife/torsen. It’ll make it worse. A 1.5-way won’t be as bad as a 2-way or spool though – the “original torque setting” (quote from below) is still greater than zero.

Here’s why- when a car is going straight, all 4 wheels are turning at the same speed. In a corner, the inside wheels are turning slower than the outside wheels. In order to initiate a turn, the outside wheels have to speed up vs. the inside. A mechanical clutch-type LSD resists the creation of this speed delta between inside and outside wheels – EVEN WITH THE THROTTLE CLOSED. An open diff doesn’t do this, nor do the stock viscous units or a helical diff like the Quaife. This resistance makes it more work for the front tires to rotate the car, hence more entry understeer.

All this isn’t necessarily the end of the world, some people like the extra “stability” while trail-braking into a corner. If I were to buy a diff for my car (which is used primarily for autocross), the OS Giken is what I’d choose.

The O.S. Giken Response: The OS Super Lock LSD Spec-S settings allow for a smooth and progressive ramp up in lock all the way to 100% lock. The OS Super Lock is unlike other traditional clutch type differentials in that the unique design allows for almost twice the number of clutch plates. More clutch disks provide more surface area to create more friction, necessary to provide the limited slip effect as well as full lock. Having more clutch plates also means that we can achieve up to 100% lock while using minimal preload on the clutch disks. This preload is what provides the “lock” people refer to when one wheel is off the ground. The preload for the OS Spec-S units is set more to supply added stability, rather than full “one-wheel performance”. The preload is mild enough that it will feel very similar to a stock open differential to the daily driver, until the torque is applied. From that point, the unit will provide a smooth and progressive lock up (in direct relation to amount of torque applied, of course) and keep the vehicle moving forward.  The Spec-S units utilize a 1.5way cam angle, meaning that the ramp-up to lock will be bias to providing a more positive lock up on acceleration and far less on deceleration, where the ramp to lock-up will serve more to stabilize the vehicle during braking/deceleration. In essence, the Spec-S will feel like an open differential that doesn’t allow for unwanted wheel spin when exiting corners or “tail wagging” during heavy straight line accelerating (as the unit will provide progressive locking at equal rates to both wheels due to the centered design of our unit). For drag users, this will translate to greater straight line acceleration and keep the rear where it is supposed to be. For track/autocross users this translates to faster corner exit speeds (progressive lock allows for earlier application of throttle) and more stability during heavy braking. In addition, due to the minimum amount of preload utilized, corner entry is essentially unaffected. Faster times will be achieved.

Both of the above comments posted from users in the forum are not necessarily incorrect, but they are not very applicable to the OS Super Lock, as it is very different from traditional clutch type LSDs.

Both situations seem to be describing the turning characteristics and controls of an OS Super Lock LSD as that of a spool or welded differential, or one of our units specifically tuned for drift (higher preload, faster lock timing, etc…). I hope that with the above explanation, your inquiring customers will understand that this is clearly not the case with the Spec-S settings.

While the above explanation mostly addresses the OS Super Lock’s locking characteristics, it should be mentioned that it also unlocks in a relatively seamless fashion. This is due to the design of our pressure ring, which forms the basis of our lock timing control system. In the scenario you mentioned of a customer potentially loosing tire traction and control due to premature lock (likely due to an over-application of torque vs. capacity of the tires when trying to make a turn at an unfavorable angle), if the customer simple lifted off the throttle or up-shifted (thus lessening the application of torque to the wheels/differential) the differential would unlock and allow for the vehicle to regain control via steering and throttle input. Granted, we do not advise any users to practice this on the street!

If any of your customers or Viper owners have any questions regarding our unit, please feel free to forward their questions over to me or have them contact us via our website at www.osgiken.net. We are always happy to spend time with customers and will answer any questions they may have.

Thank you.