HKS Transfer Case Oil Cooler Kit - 2023+ Toyota GR Corolla

If you track your GR Corolla, you probably know about the cooling issues that the Transfer Case suffers from. Oil temps get hot, and you risk damaging components and putting the unit into "Limp Mode".

The HKS Transfer Case Oil Cooler Kit is the solution to your cooling problems! It helps maintain lower oil temperatures, which in turn extend the oil's lifespan, and protects the unit from those higher temperatures under high load driving.

Transfer Case:

• It is installed at the rear of the engine and changes the direction of the driving force coming from the transaxle differential case by 90 degrees before sending it to the rear wheels.
• In the 4WD systems used in the GR Corolla, an electronically controlled coupling located in front of the rear differential adjusts the power sent to the rear wheels.
• The system constantly fine-tunes the power distribution to achieve the ideal balance for each driving mode (NORMAL, GRAVEL, TRACK).

Features:

• The dedicated pipe-type cooler ensures the transfer oil is cooled without affecting engine coolant, engine oil, or I/C cooling performance. The bracket fixing the cooler is designed to avoid obstructing airflow to the radiator and intercooler.
• HKS uses a high-load, high-flow electric oil pump, controlled by a dedicated pump controller. If the pump is operated when the oil temperature is low (high viscosity), the overcurrent protection control puts it in standby mode and automatically restarts once the oil temperature reaches an appropriate level. It’s recommended to operate the pump when the oil temperature is above 60°C to prevent overloading.
• For vehicles equipped with a transfer protection control cancellation program, selecting the TRACK mode within 1 minute of engine startup automatically activates the pump. The pump's operating status can be checked on the controller display. The kit includes wiring from the power source to the electric pump.
• The transfer oil outlet uses a specially designed banjo-type attachment that is resistant to impact damage. The banjo bolt has a PT1/8 plug hole, allowing for oil changes without removing the bolt, and can also be used as a temperature sensor mounting hole.

Pump Controller Features:

• Operating modes
  • AUTO mode (for vehicles without a transfer protection control cancellation program)
  • FULL AUTO mode (for vehicles with a transfer protection control cancellation program)
  • MANUAL mode (for maintenance)
• Current value monitoring function
  • When the pump current is above the rated value, it goes into standby mode. During standby, it operates the pump for 3 seconds every 30 seconds to monitor the current value
• Overcurrent protection function
  • Transfer protection control cancellation function (only valid for vehicles with a transfer protection control cancellation program)
  • The transfer protection control cancellation function can be used by connecting the vehicle's "4WD mode select switch" connector to the pump controller.

Usage:

We recommend activating the system just before starting sporty driving as a general guideline. Please note that wiring and operation differ between vehicles with and without the transfer protection control cancellation program. Be sure to check your vehicle's specifications before installation.

• This product is designed for circuit use where transfer oil temperatures can rise significantly. For daily driving where transfer oil isn’t heavily loaded, please keep the pump turned off.
• Even on track, avoid operating the pump when the oil temperature is still low, as this can put excessive load on the pump and piping. Use it only when oil temps are around 60°C or higher.
  If using AUTO or FULL AUTO mode and the pump frequently starts and stops, it means the oil temperature is too low. In such cases, avoid long-term use to prevent damage.
• Please use stock transfer oil or HKS G900 75W-90 gear oil. Do not use oil thicker than 75W-90, as they can overload the system.
• The transfer protection control cancellation function only works on vehicles equipped with the appropriate program. If your vehicle doesn’t have this program, do not connect the “4WD mode select switch” connector — doing so will disable 4WD.
• Some vehicle modifications are required for installation:
  • Both models may also require trimming of bumper air ducts or undercover ducts.
  • GR Corolla: Bumper reinforcement, intercooler air guide, undercover duct

Install Instructions:

27002-AT001