HKS 27002-AT001 Transfer Oil Cooler Kit for TOYOTA GR Corolla (GZEA14H) 2023-

The Transfer Unit is mounted at the rear of the engine and redirects driving force from the transaxle differential case by 90° to the rear wheels.

In the 4WD system of the GR Corolla, an electronically controlled coupling in front of the rear differential adjusts rear power distribution in real time to match the selected driving mode: NORMAL, GRAVEL, or TRACK.

Under prolonged high-load conditions, the transfer system in the GR Corolla switches to 2WD to prevent overheating.

The HKS Transmission Oil Cooler lowers oil temperatures, extends oil life, and protects the transfer unit from damage.

Vehicles equipped with the Transfer Protection Cancel Program can maintain full-time 4WD even on track by disabling limp mode. (Using this feature may void the warranty — please consult your dealer.)

Components:

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

Features:

• Dedicated pipe-type cooler operates independently of engine coolant, engine oil, and intercooler systems.
• Bracket is designed to prevent obstruction of radiator and intercooler airflow.
• High-load, high-flow electric pump controlled by a dedicated controller enters standby when oil is too cold and automatically resumes at appropriate temperatures (recommended use above 60°C).
• With the cancel program installed, activating TRACK mode within one minute of engine start will auto-activate the pump. Pump status is shown on the controller display.
• Special banjo-type oil outlet resists impact. The banjo bolt includes a PT1/8 plug hole for easy oil changes and temperature sensor installation.

Pump Controller Functions:

• Operating Modes:
  • AUTO mode – for vehicles without the cancel program
  • FULL AUTO mode – for vehicles with the cancel program
  • MANUAL mode – for maintenance use
• Current Monitoring: If current exceeds safe levels, the pump enters standby and cycles briefly every 30 seconds to check current draw.
• Overcurrent Protection: Ensures pump safety under abnormal load.
• Cancel Program Integration: Connects to the vehicle's “4WD mode select switch” when the program is installed.

Usage Notes:

• Intended for track use where transfer oil temperatures can be high.
• Turn the pump off during regular daily driving.
• Do not run the pump with cold oil (below 60°C).
• If frequent pump activation/deactivation occurs in AUTO/FULL AUTO mode, the oil is too cold — avoid extended use in this condition.
• Use only factory transfer oil or HKS G900 75W-90. Thicker oils can overload the system.
• Do not connect the “4WD mode select switch” if the vehicle lacks the cancel program — doing so disables AWD.
• Minor modifications required for installation:
  • Bumper reinforcement trimming
  • Intercooler air guide adjustment
  • Undercover duct trimming

Tip: Activate the system just before entering sporty driving for optimal performance.

Note: Wiring and function differ depending on whether the cancel program is installed. Confirm vehicle specifications before installation.

Track Test Data – Fuji Speedway (GR Corolla):

• Without cooler: oil temperature rose to approx. 150°C and continued to increase.
• With cooler: temperature stabilized around 125°C; expected stable temp ~130°C.
• Estimated difference: approx. 80°C under continuous load.

Vehicle Compatibility:

• GR Corolla Japan spec: from March 2025
• GR Corolla North American spec: from August 2024