Should the front Super Lock LSD for GD and GR cars be fitted with the rear?

Many owners fit both, because the front Super Lock LSD for GD and GR STI cars and the rear unit together give a clutch-type locking differential at both axles. The front unit alone helps most on loose surfaces and tight exits where a front tire unloads, and installing both at once saves a second round of labor.

Will it make the steering heavy?

There is more feedback through the wheel under hard acceleration, because both front tires are now driving. The low preload and progressive lock of the Super Lock keep that effect moderate, and on gravel or a tight circuit the gain in front-axle traction outweighs the extra steering effort.

Is it useful on a street STI?

Less so. The gains show at the limit of grip, on loose surfaces and over curbs. A street STI driven moderately sees little change. For rallycross, gravel stages or time attack it is one of the most effective drivetrain changes available.

Does installation require opening the gearbox?

Yes. The front differential sits inside the STI six-speed transaxle, so fitting it means removing and splitting the gearbox. That is work for a drivetrain specialist, and it is a good time to inspect synchros and bearings as well. Plan the job accordingly.

Can it be retuned later?

Yes. OS Giken rebuilds and retunes Super Lock units in-house, changing initial torque with cone springs, lock timing with pressure ring springs and ramp angle with the pressure ring and iron cross, so the unit can be set for gravel or tarmac.

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Description

OS Giken Front Super Lock LSD for GD / GR Subaru Impreza WRX STI

OS Giken’s Front Super Lock LSD for GD / GR Subaru Impreza WRX STI fits inside the six-speed transaxle and puts a clutch-type differential on the axle that steers the car out of every corner. With the driver-controlled center differential locked up for traction, the front axle carries a large share of the EJ257’s torque, and a front tire that goes light over a curb or crest is where that torque escapes. OS Giken’s patented pressure ring keeps both front tires driving. OS Giken USA lists it for both the GDB and the GRB generations. It suits rallycross, gravel and tight time-attack circuits.

Design and Performance

OS Giken threads the friction plates onto splines that pass through the side gears, giving up to twice the plate count of competing designs. That plate area lets the unit run a low preload while still building to full lock smoothly under power. The case is machined from a single billet and the gears are raw-forged and heat treated.

Features

Clutch-type front differential for the STI six-speed transaxle
Light preload so the car stays easy to drive on the road
Patented OS Giken pressure ring for progressive lock
Up to twice the friction plates of competing designs
Billet case and raw-forged gears
Retunable for initial torque, lock timing and ramp angle

Applications

Subaru Impreza WRX STI: GD | 2004-2007 | 2.5L EJ257 turbo
Subaru Impreza WRX STI: GR | 2008-2014 | 2.5L EJ257 turbo

Notes

This is the front unit; the OS Giken Rear Super Lock LSD for GD / GR Subaru Impreza WRX STI is sold separately
Fitting requires removing and opening the transaxle; installation labor is not included

Frequently Asked Questions

Should the front Super Lock LSD for GD and GR cars be fitted with the rear? Many owners fit both, because the front Super Lock LSD for GD and GR STI cars and the rear unit together give a clutch-type locking differential at both axles. The front unit alone helps most on loose surfaces and tight exits where a front tire unloads, and installing both at once saves a second round of labor.
Will it make the steering heavy? There is more feedback through the wheel under hard acceleration, because both front tires are now driving. The low preload and progressive lock of the Super Lock keep that effect moderate, and on gravel or a tight circuit the gain in front-axle traction outweighs the extra steering effort.
Is it useful on a street STI? Less so. The gains show at the limit of grip, on loose surfaces and over curbs. A street STI driven moderately sees little change. For rallycross, gravel stages or time attack it is one of the most effective drivetrain changes available.
Does installation require opening the gearbox? Yes. The front differential sits inside the STI six-speed transaxle, so fitting it means removing and splitting the gearbox. That is work for a drivetrain specialist, and it is a good time to inspect synchros and bearings as well. Plan the job accordingly.
Can it be retuned later? Yes. OS Giken rebuilds and retunes Super Lock units in-house, changing initial torque with cone springs, lock timing with pressure ring springs and ramp angle with the pressure ring and iron cross, so the unit can be set for gravel or tarmac.

About OS Giken

OS Giken was founded in Okayama, Japan in 1973 by Masaharu Okazaki. It built the TC16 and TC24-B1 DOHC cylinder heads for Nissan L-series engines, began making multi-plate racing clutches in 1982 and started supplying OEM limited-slip differentials in 1983. Development of the Super Lock LSD began in 1997, and of the OS-88 sequential gearbox for the Skyline GT-R in 1998.

Additional Information

The Bulletproof Automotive website contains many thousands of products purchased in multiple different currencies. All of the prices are entered manually and accurately at the time of entry. Due to the consistently fluctuating international exchange rates, at times prices may not be able to be honored at their original intended rate. We apologize for any inconvenience this may cause, unfortunately our website is unable to compensate dynamically for what can at times be volatile changes in the cost of items due to currency values fluctuating, changes in prices from suppliers, changes in shipping and import duties, and other factors. Rest assured that any order you place on line will be at zero risk to you in this area. If in the event your order cannot be fulfilled at the original intended website price we will offer you a 100% refund, no questions asked. We will continue to do our best to maintain updated prices and we will always continue to offer our price match guarantees as well to ensure our prices are always the best for you. In short, prices may change without notice. It is always advised to give us a call prior to placing your order online to confirm availability and to confirm current pricing.

Shipping Policy

Items that are in stock in the US, either at Bulletproof’s warehouse or at a supplier’s warehouse, are generally delivered within 7-10 days. Special order items from overseas take considerably longer. As a courtesy Bulletproof offers delivery estimates to our customers which take into consideration manufacturer availability and shipping schedule. These estimates represent our best guess based on previous orders from the manufacturer and do not in any way imply a guaranteed delivery window. Many manufacturers work in a “just in time” inventory system and often take 2-20+ weeks to produce an item once an order is submitted. All deliverable items are then sent to our Japanese warehouse. Bulletproof ships a minimum of one full ocean freight container every month from Japan, oftentimes more than one a month. Ocean freight takes an average of 4 weeks. Typically it breaks down to one week in Japan for paperwork and customs, two weeks by boat and one week in US customs/clearance. Due to the wide number of variables between manufacturer and shipping schedules, delivery estimates are simply just that – estimates. We attempt to estimate conservatively and we usually deliver faster than our estimates suggest. It is not Bulletproof’s policy to guarantee delivery time of any special order item, this is impossible for us to do. By ordering you acknowledge that there is no required delivery ETA and an order may not be canceled or altered due to manufacturing or shipping delays, all ETA’s are provided as a best guess only. Please review the full Terms & Conditions here.

BP Pricing Difference

We do pricing a little differently on our JDM brands and we believe in making things simple and clear. No hidden fees or surcharges. Every price you see includes the shipping cost to our office in Los Angeles, California and all the associated taxes/duties/fees for bringing the products into the US. The only shipping you ever pay is from our facility in the US to your location. Be wary of resellers that don’t include the cost of international shipping in their pricing on JDM parts. While we believe we’ll always have the lowest all-in price on JDM products, we offer a price match guarantee for all authentic parts purchased from authorized dealers as well. For many international customers, it’s much more affordable to ship from the USA than from Japan directly, as the air freight and ocean freight costs are typically much less. However, for customers looking to ship directly from Japan outside of North America, or domestically in Japan, we can provide pricing specifically for that scenario. Please do not hesitate to contact us with any pricing questions or concerns. Please email us at sales@bulletproofautomotive.com with any inquiries.

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OS Giken Front Super Lock LSD for GD / GR Subaru Impreza WRX STI [SB041-HA01]

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OS Giken Front Super Lock LSD for GD / GR Subaru Impreza WRX STI

Design and Performance

Features

Applications

Notes

Frequently Asked Questions

About OS Giken

Reviews