Description

The HKS Transfer Oil Cooler Kit is a comprehensive, electronically managed cooling system designed to protect the critical transfer case of the GR Yaris during sustained high-load driving, such as on a circuit. It prevents the transfer oil from overheating—which triggers the factory’s protective “2WD limp mode”—and allows for continuous 4WD operation. By integrating a dedicated front-mounted cooler, a high-flow electric pump, and an intelligent controller, this system stabilizes oil temperatures, extends component life, and unlocks the car’s full performance potential in track and competitive environments.

Product Overview & Purpose

The GR Yaris’s sophisticated 4WD system uses a transfer case to direct power to the rear wheels. Under extreme conditions (e.g., repeated laps), the transfer oil can exceed 150°C, forcing the car into a protective front-wheel-drive mode to prevent damage. This kit actively cools the transfer oil, maintaining safe temperatures (around 100°C in testing) to prevent this limp mode, ensuring consistent all-wheel-drive traction and performance for the duration of a session.

Product Highlights

🛡️ Prevents 2WD Limp Mode & Enables Continuous 4WD
The primary function is to eliminate performance-limiting overheating. By stabilizing oil temperatures, it prevents the factory’s transfer protection control from engaging, allowing you to drive aggressively in 4WD (including TRACK mode) without interruption—a critical advantage for lap times and driver confidence.

🌡️ Intelligent, Multi-Mode Pump Controller
The kit includes a sophisticated controller with multiple operation modes tailored to your vehicle:

• FULL AUTO Mode (for 2025+ models): Automatically activates the cooler when the vehicle’s TRACK mode is engaged, seamlessly integrating with the factory’s transfer protection cancellation program.

• AUTO & MANUAL Modes: Provides flexible control for earlier models or specific use cases. Features overcurrent protection and automatic standby/resume functions to protect the pump during cold starts.

🔧 Dedicated, High-Efficiency Cooling System

• Front-Mounted Cooler: A dedicated, pipe-type cooler is strategically placed with minimal frontal area to avoid blocking airflow to the radiator and intercooler.

• High-Flow HKS Electric Pump: Manufactured in-house for reliability, it ensures consistent oil circulation under high-load conditions.

• Robust Installation: Includes a specially designed impact-resistant banjo bolt fitting at the transfer case with a port for oil changes or temperature sensor installation.

📈 Proven Track Performance
Internal testing at Fuji Speedway demonstrated a dramatic temperature reduction. Without the cooler, oil temps rose to ~150°C, triggering the test’s end. With the HKS cooler installed, temperatures stabilized at approximately 100°C, allowing for continuous running and estimating a ~50°C reduction in peak operating temperature.

Technical Specifications & Compatibility

• Product Name: Transfer Oil Cooler Kit

• Model Code: 27002-AT002

• Compatibility: Toyota GR Yaris (GXPA16, G16E-GTS, September 2020+). Controller function varies by model year.

• Key Feature: Active oil cooling to prevent transfer overheating and 2WD limp mode.

• Controller Modes: FULL AUTO (for 2025+ with cancellation program), AUTO, MANUAL.

• Includes: Cooler, electric pump, pump controller, all piping, wiring, brackets, and hardware.

• Installation Note: Requires modification to factory air guides and undercover. Estimated installation: 8 hours.

Performance Philosophy

• Goal: To solve a fundamental performance and reliability limitation of the GR Yaris’s 4WD system when pushed to its limits. The focus is on systematic protection, performance preservation, and intelligent integration with factory controls.

• Focus: A mandatory competition and track-day modification. It is essential for any driver who uses their GR Yaris on track, for time attack, or in any situation where sustained high load on the drivetrain is expected. It transforms the car from a hot hatch with a thermal Achilles’ heel into a resilient, repeatable performance tool.

Installation & Usage Notes

• 🔧 Professional Installation REQUIRED
  This is a complex installation involving the transfer case, fluid system, electrical wiring, and modification of body panels. Must be installed by a highly qualified professional shop with experience in GR Yaris systems and meticulous bleeding procedures.

• ⚠️ Critical Model Year & Usage Guidelines

  • 2025+ Models (with Cancellation Program): Can utilize the seamless FULL AUTO mode linked to TRACK mode.

  • Pre-2025 Models: Use AUTO or MANUAL modes. Do not connect the TRACK mode signal wire.

  • Oil & Temperature: Use only recommended 75W-90 gear oil. Do not activate the pump below 60°C to avoid pump overload.

  • Warranty Impact: Enabling the transfer protection cancellation function will void the vehicle manufacturer’s warranty.