HKS 4WD Transfer Oil Cooler Kit – Toyota GR Yaris

The HKS Transfer Oil Cooler is designed for the GR Yaris GXPA16 to control transfer oil temperatures during continuous high-load driving. The factory transfer system switches to 2WD when temperatures rise. This kit keeps the transfer unit cooler, protects the drivetrain, and maintains stable performance during circuit use.

What the Transfer Unit Does

The transfer unit sits behind the engine and redirects drive force 90° toward the rear wheels. On the GR Yaris, an electronically controlled coupling adjusts rear-wheel power based on the selected mode (NORMAL, GRAVEL, TRACK). Under sustained load, the system can disable 4WD to prevent overheating.

Product Overview

The HKS Transfer Oil Cooler lowers oil temperatures and extends transfer oil life. It helps prevent limp mode and maintains 4WD functionality under continuous track driving. Vehicles with the Transfer Protection Cancel Program can run full-time 4WD during circuit use. (Warranty may be affected — check your terms.)

Components

• Transfer cooler pipe
• Oil filter
• Electric oil pump
• Mounting bracket
• Pump controller
• Hoses, harness, and hardware

Key Features

• Dedicated pipe-type cooler that does not affect engine coolant, engine oil or intercooler efficiency
• High-flow electric oil pump with overcurrent protection and automatic restart
• Pump activation linked to TRACK mode when used with the cancellation program
• Banjo-type outlet fitting with PT1/8 port for oil changes or temperature sensors
• Bracket and cooler placement designed to avoid blocking radiator or intercooler flow

Pump Controller Modes

• AUTO: For vehicles without the cancel program
• FULL AUTO: For vehicles with the cancel program
• MANUAL: For maintenance
• Current-monitoring and overcurrent protection
• Transfer protection cancel function (only for compatible vehicles)

Usage Notes

• Use for circuit driving where transfer temps rise significantly
• Do not operate the pump below ~60°C oil temperature
• If the pump cycles repeatedly, the oil is too cold
• Use OEM transfer oil or HKS G900 75W-90
• Thicker oils may overload the system
• Do not connect the 4WD switch to the controller on vehicles without the cancel program
• Some trimming of ducts or undercovers may be required

Performance Testing

HKS testing at Fuji Speedway showed a temperature reduction of approximately 50°C during continuous laps. Without the cooler, transfer oil exceeded 150°C. With the cooler installed, temperature stabilised near 100°C under the same conditions.

Installation Instructions

Full install guide:
HKS Installation Manual – 27002-AT002