{"product_id":"os-giken-super-lock-rear-lsd-subaru-impreza-wrx-sti-2004-2021","title":"OS Giken Super Lock Rear LSD for 2004-2021 Subaru Impreza WRX STI GDB GRB","description":"\u003ch4\u003ePrecision Locking Differential Technology for the Subaru WRX STI\u003c\/h4\u003e\u003cp\u003eThe OS Giken SB041-HA Super Lock LSD is a rear limited-slip differential engineered for the Subaru Impreza WRX STI GDB and GRB chassis, covering 2004 through 2021 model years on the EJ25 powertrain. OS Giken's patented pressure ring design allows for smooth, progressive locking behavior combined with a fully capable 100 percent lock when demanded by aggressive driving inputs. The SB041-HA uses a spline-through-side-gear architecture that accommodates up to twice as many friction plates as competing designs, translating to superior durability and consistent performance on street and track.\u003c\/p\u003e\u003ch4\u003eKey Features\u003c\/h4\u003e\u003cul\u003e\n\u003cli\u003eOS Giken patented pressure ring design for smooth progressive locking\u003c\/li\u003e\n\u003cli\u003eSpline-through-side-gear construction for maximum friction plate count\u003c\/li\u003e\n\u003cli\u003e1.5-way ramp configuration: 25 degree acceleration, 38 degree deceleration\u003c\/li\u003e\n\u003cli\u003eLow preload with full 100 percent lock capability\u003c\/li\u003e\n\u003cli\u003e20 total friction plates for exceptional torque capacity\u003c\/li\u003e\n\u003cli\u003eRaw-forged gears and high-grade steel alloy construction\u003c\/li\u003e\n\u003cli\u003eCompatible with EJ25-powered GDB and GRB STI chassis\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch4\u003eVehicle Fitment\u003c\/h4\u003e\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eYear Range\u003c\/th\u003e\n\u003cth\u003eMake\u003c\/th\u003e\n\u003cth\u003eModel\u003c\/th\u003e\n\u003cth\u003eTrim\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e2004-2007\u003c\/td\u003e\n\u003ctd\u003eSubaru\u003c\/td\u003e\n\u003ctd\u003eImpreza\u003c\/td\u003e\n\u003ctd\u003eWRX STI\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e2008-2014\u003c\/td\u003e\n\u003ctd\u003eSubaru\u003c\/td\u003e\n\u003ctd\u003eImpreza\u003c\/td\u003e\n\u003ctd\u003eWRX STI\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e2008-2014\u003c\/td\u003e\n\u003ctd\u003eSubaru\u003c\/td\u003e\n\u003ctd\u003eImpreza\u003c\/td\u003e\n\u003ctd\u003eWRX STI Limited\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e2010-2013\u003c\/td\u003e\n\u003ctd\u003eSubaru\u003c\/td\u003e\n\u003ctd\u003eImpreza\u003c\/td\u003e\n\u003ctd\u003eWRX STI Special Edition\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003ch4\u003eSpecifications\u003c\/h4\u003e\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eDetail\u003c\/th\u003e\n\u003cth\u003eValue\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003ePart Number\u003c\/td\u003e\n\u003ctd\u003eSB041-HA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBrand\u003c\/td\u003e\n\u003ctd\u003eOS Giken\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eType\u003c\/td\u003e\n\u003ctd\u003eLimited Slip Differential\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLocation\u003c\/td\u003e\n\u003ctd\u003eRear\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLSD Style\u003c\/td\u003e\n\u003ctd\u003e1.5-Way (25\/38 Ramps)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLock Timing\u003c\/td\u003e\n\u003ctd\u003e336\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTotal Plates\u003c\/td\u003e\n\u003ctd\u003e20\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePreload\u003c\/td\u003e\n\u003ctd\u003e10S\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFitment\u003c\/td\u003e\n\u003ctd\u003eSubaru WRX STI GDB\/GRB EJ25\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCondition\u003c\/td\u003e\n\u003ctd\u003eNew\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eUPC\u003c\/td\u003e\n\u003ctd\u003eN\/A\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003ch4\u003eWhat's Included\u003c\/h4\u003e\u003cul\u003e\n\u003cli\u003eOS Giken SB041-HA Super Lock LSD unit (rear)\u003c\/li\u003e\n\u003cli\u003eRequired internal hardware\u003c\/li\u003e\n\u003cli\u003eInstallation documentation\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch4\u003eAbout OS Giken\u003c\/h4\u003e\u003cp\u003eOS Giken is a Japanese precision manufacturer with a long history in motorsport-grade drivetrain components. Their LSD technology is used in Super GT, rally, and time attack competition globally, and is recognized for combining low preload street comfort with race-level locking performance in the same unit.\u003c\/p\u003e\u003ch4\u003eRelated Parts on Our Site\u003c\/h4\u003e\u003cul\u003e\u003cli\u003e\u003ca href=\"\/products\/os-giken-htr-twin-plate-clutch-civic-type-r-fk8\"\u003eOS Giken HTR Twin Plate Clutch for Honda Civic Type R FK8\u003c\/a\u003e\u003c\/li\u003e\u003c\/ul\u003e\u003ch4\u003eFrequently Asked Questions\u003c\/h4\u003e\u003cstrong\u003eWhat is the SB041-HA?\u003c\/strong\u003e\u003cp\u003eThe OS Giken SB041-HA is a rear Super Lock limited-slip differential designed for the Subaru Impreza WRX STI GDB and GRB chassis with EJ25 engines. It uses OS Giken's patented pressure ring technology to deliver smooth, progressive locking with full 100 percent lock capability when required.\u003c\/p\u003e\u003cstrong\u003eWhat does 1.5-way mean on the OS Giken SB041-HA LSD?\u003c\/strong\u003e\u003cp\u003eA 1.5-way LSD uses different ramp angles for acceleration and deceleration. The SB041-HA uses 25 degree ramps on acceleration and 38 degree ramps on deceleration, providing aggressive traction on power while offering partial lockup during lift-off for predictable corner entry behavior.\u003c\/p\u003e\u003cstrong\u003eIs the OS Giken SB041-HA suitable for daily street driving on a WRX STI?\u003c\/strong\u003e\u003cp\u003eYes. The SB041-HA's low preload setting makes it smooth enough for daily street use, while the progressive pressure ring engagement avoids the harsh binding found in some high-preload clutch-type LSDs. It is a practical upgrade for drivers who use their STI on both street and occasional track days.\u003c\/p\u003e\u003cstrong\u003eDoes the SB041-HA require any special fluid for the rear differential?\u003c\/strong\u003e\u003cp\u003eOS Giken recommends using appropriate gear oil in the rear differential after installation. Consult the OS Giken installation documentation for the specific viscosity and capacity recommendations for the GDB\/GRB rear differential housing.\u003c\/p\u003e\u003cstrong\u003eWill the OS Giken SB041-HA fit both GDB and GRB Subaru STI chassis?\u003c\/strong\u003e\u003cp\u003eYes. The SB041-HA is designed to fit both the GDB (2004 to 2007) and GRB (2008 to 2014) Subaru Impreza WRX STI chassis that use the EJ25 engine with the rear differential housing common to both generations.\u003c\/p\u003e\u003cstrong\u003eHow does the OS Giken Super Lock LSD compare to a Cusco or Kaaz LSD for the STI?\u003c\/strong\u003e\u003cp\u003eThe OS Giken patented pressure ring design allows for more friction plates than most competitor designs, enabling higher torque capacity and longer service intervals. The progressive locking characteristic of the SB041-HA is frequently cited as more refined than equivalent Cusco or Kaaz units in the same application.\u003c\/p\u003e\u003cstrong\u003eHow long does the OS Giken SB041-HA last before requiring a rebuild?\u003c\/strong\u003e\u003cp\u003eOS Giken LSDs are built with raw-forged gears and high-grade steel components rated for extended motorsport service intervals. Rebuild frequency depends on usage intensity, but track-focused drivers should inspect friction plate wear annually and replace plates per OS Giken service guidelines.\u003c\/p\u003e\u003cstrong\u003eCan I install the SB041-HA myself or does it require professional installation?\u003c\/strong\u003e\u003cp\u003eRear differential replacement on the Subaru STI requires removing the rear differential and properly torquing ring gear and bearing preload. This work is best performed by a qualified Subaru specialist or performance shop familiar with GDB\/GRB drivetrain assembly to ensure correct preload and backlash settings.\u003c\/p\u003e\u003ch4\u003eInstallation Instructions\u003c\/h4\u003e\u003col\u003e\n\u003cli\u003eRaise and support the vehicle safely on jack stands with the rear wheels off the ground.\u003c\/li\u003e\n\u003cli\u003eDrain the rear differential fluid and remove the driveshaft and axle shafts.\u003c\/li\u003e\n\u003cli\u003eUnbolt and remove the rear differential assembly from the subframe.\u003c\/li\u003e\n\u003cli\u003eDisassemble the differential housing and remove the factory LSD or open differential unit.\u003c\/li\u003e\n\u003cli\u003eInstall the OS Giken SB041-HA Super Lock LSD into the housing, setting bearing preload and ring gear backlash per specification.\u003c\/li\u003e\n\u003cli\u003eReassemble the differential housing with all fasteners torqued to Subaru specification.\u003c\/li\u003e\n\u003cli\u003eReinstall the differential, driveshaft, and axle shafts.\u003c\/li\u003e\n\u003cli\u003eRefill with recommended gear oil and check for leaks before returning to service.\u003c\/li\u003e\n\u003c\/ol\u003e","brand":"OS Giken","offers":[{"title":"Default Title","offer_id":46059177312335,"sku":"OSGSB041-HA","price":1428.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1062\/7920\/files\/OS_Giken_Super_Lock_LSD_Nissan_Skyline_GT-R_BNR34.jpg?v=1784215678","url":"https:\/\/www.blackopsautoworks.com\/products\/os-giken-super-lock-rear-lsd-subaru-impreza-wrx-sti-2004-2021","provider":"Black Ops Auto Works","version":"1.0","type":"link"}