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Improve traction and progressive lockup with a clutch-type limited-slip differential engineered for the stated differential housing and drivetrain. Match OS Giken part TY421-HA by complete vehicle application and every transmission, differential, release, spline, plate, fluid, and companion-part requirement before ordering.
Key Features
- High-Capacity Clutch Pack: 8 initial torque plates plus 8 reaction plates deliver consistent torque bias and resist wear.
- Shot-Peened Gears: SCM415 alloy steel gears with carburizing treatment handle extreme torque while minimizing noise.
- 2-Way Locking: Engages full lock on acceleration and deceleration sending power to the wheel with grip.
- Direct Bolt-In Design: Matches OEM dimensions and spline count for seamless swap with stock 4.1 final drive.
- Yes direct fit for all ZN6 chassis 86 FR-S BRZ models 2013-2021 regardless of submodel or transmission.
- Drain OEM fluid remove stock differential and transfer internals to LSD carrier.
Fitment
| Years | Make | Model | Application Notes |
|---|---|---|---|
| 2013-2016 | Scion | FR-S | Confirm chassis, engine, transmission, differential housing, axle or spline, final drive, release system, and every OS Giken application note |
| 2013-2017 | Subaru | BRZ | Confirm chassis, engine, transmission, differential housing, axle or spline, final drive, release system, and every OS Giken application note |
| 2017 | Toyota | 86 | Confirm chassis, engine, transmission, differential housing, axle or spline, final drive, release system, and every OS Giken application note |
Searchable fitment is limited to year, make, and model. Chassis, engine, transmission, differential, spline, trim, and release-system requirements remain application notes.
Specifications
| Brand | OS Giken |
|---|---|
| Manufacturer Part Number | TY421-HA |
| Product Type | Differentials |
| Fitment Type | Vehicle Specific |
| Condition | New |
What's Included
One new OS Giken product in the exact configuration and package quantity identified by part TY421-HA. Bearings, seals, fluids, flywheel, clutch, release components, alteration kits, tools, fasteners, and other companion parts are included only when expressly stated.
About OS Giken
OS Giken designs and manufactures performance clutches, limited-slip differentials, drivetrain components, gear oil, and precision service tools in Japan. Exact transmission, differential, spline, and release-system matching is essential.
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Frequently Asked Questions
Will OS Giken TY421-HA fit my vehicle?
Match the year, make, and model in the Fitment table, then confirm chassis, engine, transmission, differential housing, axle or spline, final drive, release system, and every OS Giken application note.
Does OS Giken TY421-HA replace every factory differential?
No. Confirm the exact differential housing, ring-gear size and bolt pattern, axle or output spline, final drive, transmission, factory differential type, and any required bearings or setup parts.
Does OS Giken TY421-HA require professional setup?
Yes. Differential installation requires inspection, measured bearing preload, backlash and contact-pattern setup, correct fastener torque, approved fluid, and verification after the first heat cycles.
Installation Instructions
Follow the current OS Giken instructions for part TY421-HA and the vehicle service manual. Support the vehicle safely, verify every mating interface before assembly, use new seals and specified hardware where required, apply the correct lubricant and torque values, measure all required clearances and adjustments, then complete the prescribed break-in and post-installation inspection.
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