OS Giken Limited Slip Differential
2013–2016 Scion FR-S, 2017–2018 Toyota 86, 2013–2018 Subaru BRZ (Manual Transmission)
TY421-HA
Overview:
The OS Giken Limited Slip Differential (LSD) TY421-HA is engineered specifically for the manual transmission variants of the Scion FR-S (2013–2016), Toyota 86 (2017–2018), and Subaru BRZ (2013–2018). This high-performance LSD is the result of over four years of dedicated research and development, culminating in the revolutionary OS Super Lock design. It offers drivers a smooth, progressive, and quiet locking experience that enhances traction and handling on both street and track environments.
Designed for enthusiasts seeking improved cornering stability, power delivery, and overall driving confidence, the OS Giken LSD transforms the driving dynamics of these popular sports cars without compromising everyday drivability.
Key Features:
The OS Giken Super Lock LSD incorporates advanced engineering and patented technology to deliver superior performance and durability. Key features include:
- Capacity to house up to 28 friction plates—twice as many as many competitor LSDs—enabling true 100% lock capability.
- Patented pressure ring design that ensures smooth, progressive locking action for predictable traction control.
- Miniaturized pressure ring and innovative spline-through-side-gear design for compact fitment and enhanced durability.
- Relief cut-out in the LSD case to reduce cone spring degradation and extend component life.
- All components chemically heat treated and constructed from high-grade steel alloy for maximum strength and longevity.
- Raw-forged gears and precision-machined clutch disks with tight tolerances to minimize warpage and ensure consistent performance.
- Single billet-machined LSD case for uniformity and structural integrity.
- Low preload setting that provides an open-differential feel during slow-speed maneuvers while delivering full lock under load.
- Ultra-quiet operation with smooth, progressive locking suitable for street and racing applications.
- Adjustable initial torque, lock timing, and ramp angles via interchangeable springs and components for tailored performance.
Construction & Design:
The OS Giken LSD is meticulously crafted using premium materials and precision manufacturing techniques. Each component undergoes chemical heat treatment to enhance durability and wear resistance. The gears are raw-forged to withstand high torque loads, while clutch disks are simultaneously machined on both sides to maintain perfect flatness and reduce warping.
The LSD case is machined from a single billet piece, ensuring consistent quality and strength throughout. The innovative spline-through-side-gear design allows for an unprecedented number of friction plates, significantly increasing locking capacity without compromising fitment. Additionally, the patented pressure ring and relief cut-out design minimize spring fatigue, resulting in a longer-lasting, more reliable differential.
Performance & Sound
The OS Giken Super Lock LSD delivers a driving experience that balances performance with refinement. Its progressive locking mechanism provides seamless power transfer to the drive wheels, improving traction during aggressive cornering and acceleration. At low speeds, the LSD behaves like an open differential, maintaining smooth and predictable handling for everyday driving.
Thanks to its precision engineering and high-quality materials, the LSD operates with minimal noise, avoiding the clunky or harsh sounds often associated with aftermarket differentials. This makes it an excellent choice for drivers who want enhanced performance without sacrificing comfort or street manners.
Installation & Fitment:
This LSD is designed as a direct fit replacement for the manual transmission models of the Scion FR-S (2013–2016), Toyota 86 (2017–2018), and Subaru BRZ (2013–2018). Installation requires no modifications to the vehicle’s drivetrain or suspension components. Due to the precision manufacturing and high-quality materials, no break-in period or rebuild is necessary after installation.
For optimal results, professional installation is recommended to ensure proper setup and adjustment of preload and lock timing according to driving preferences and vehicle setup.
What's Included:
- OS Giken Super Lock Limited Slip Differential (TY421-HA)
- Installation instructions and adjustment guidelines
- Standard cone springs and pressure ring springs for baseline setup
Ideal For:
The OS Giken LSD is ideal for driving enthusiasts and racers who demand superior traction, handling, and durability from their Scion FR-S, Toyota 86, or Subaru BRZ. It is perfectly suited for street performance, spirited driving, and various motorsport disciplines where precise power delivery and cornering stability are critical.
Whether upgrading from an open differential or replacing a worn factory LSD, this unit offers a significant improvement in vehicle dynamics while maintaining smooth operation and everyday usability.
