Description

■Product overview

• The transfer oil temperature of the GR Yaris’ transfer case is prone to rising during continuous high-load driving on a circuit, etc., so a protective control (transfer protection control) is adopted that switches the vehicle to 2WD to prevent the transfer oil temperature from becoming abnormally high.
• HKS TRANSFER OIL COOLER was developed to extend the life of transfer oil and protect the transfer, focusing on the fact that transfer oil temperature easily rises.
• For vehicles equipped with the Transfer Protection Control Cancellation Program, it is possible to enable the Cancellation Program (cancel the 2WD mode), so the vehicle will not switch to 2WD even when driving continuously on a circuit. (If the Cancellation Program is enabled, the vehicle manufacturer’s warranty will be voided. Please check your vehicle’s warranty policy for details.)

Vehicles equipped with the Transfer Protection Control Cancellation Program

• Domestic model: April 2025 onwards

*Transfer protection control is not installed on vehicles manufactured between August 2020 and December 2020.

■What is transfer?

• It is installed behind the engine and changes the direction of the driving force input from the transaxle differential case by 90 degrees before outputting it rearward.
• The 4WD system installed in the GR Yaris controls the drive force to the rear axle using an electronically controlled coupling installed in front of the rear differential.
• This mechanism constantly adjusts the driving force to ensure ideal driving force distribution in each mode (NORMAL, GRAVEL, TRACK).

■ Parts

■Features

• A dedicated pipe-type cooler is used to ensure reliable cooling of the transfer oil without affecting the engine coolant, engine oil, or I/C cooling performance. The bracket that secures the cooler is designed to minimize the frontal projection area so as not to obstruct the flow of cooling air. (This minimizes the impact of cooling air on the radiator and intercooler.)
• The oil pump is manufactured in-house by HKS and is an electric type that can withstand high loads and has a high flow rate.
• A dedicated pump controller is included. Even if the pump is activated when the oil temperature is low (high viscosity), the overcurrent protection control will put the pump into standby mode, but it will automatically resume operation once the oil temperature reaches the appropriate level.
  (Note: To avoid overloading the pump, we recommend activating the pump when the oil temperature is 60°C or higher.)
  In addition, for vehicles equipped with a transfer protection control cancellation program, the pump will automatically activate upon detecting the transfer protection control cancel signal (pressing the TRACK button within one minute of starting the engine). The pump’s operating status can be checked on the dedicated controller’s display. Wiring from the power source to the electric pump is also included.
• A specially designed banjo-type attachment is used for the transfer oil outlet. It is designed to be resistant to damage even in the unlikely event of an impact from the underside of the vehicle. The banjo bolt has a PT1/8 plug hole, so oil can be changed without removing the banjo bolt. It can also be used as a temperature sensor mounting hole.

■Pump controller function

• The pump controller has the following operating modes and functions:
• Operation mode
  AUTO mode (mode for vehicles not equipped with transfer protection control cancellation program)
  FULL AUTO mode (mode for vehicles equipped with transfer protection control cancellation program)
  MANUAL mode (for maintenance)
• Current value monitoring function
  (When the pump current exceeds the rated value, it goes into standby mode. During standby, the pump operates for 3 seconds every 30 seconds to monitor the current value)
• Overcurrent protection function
• Transfer protection control cancellation function (only available on vehicles equipped with the transfer protection control cancellation program)
  The transfer protection control cancellation function can be used by connecting the pump controller to the vehicle’s “4WD mode select switch” connector.

■Precautions for use

• This product is intended for use in circuit driving where the transfer oil temperature can be high. For general driving where the transfer oil is not subjected to high loads, please turn the pump off.
• Do not operate the pump when the transfer oil temperature is low, even on a circuit, as this will overload the pump and piping. (As a guideline, operate the pump at 60°C or above.)
• If the pump repeatedly starts and stops due to the current monitoring function while operating in AUTO mode or FULL AUTO mode, the transfer oil temperature is low. Do not use the pump in this state for long periods of time.
• Please use genuine transfer oil or our gear oil (G900 75W-90).
  Do not use high viscosity oils exceeding 75W-90 as they will overload the pump and piping.
• The Transfer Protective Control Cancellation function is only effective on vehicles equipped with the Transfer Protective Control Cancellation Program. If used on a vehicle that does not have this program, do not connect the vehicle’s “4WD Mode Select Switch” connector. (4WD mode switching will not be possible.)
• Installation of this product requires modification to certain areas of the vehicle (radiator front air guide, radiator upper air guide plate, radiator air guide right, engine under-cover duct).

• Without the transfer oil cooler installed, the oil temperature was still rising, but the test was terminated when the oil temperature rose to approximately 150°C.
• With the transfer oil cooler installed, the oil temperature stabilized at around 100°C, so the test was terminated.
• Based on these results, if we estimate the temperature at which the oil temperature will saturate if the race continues, the difference in temperature with and without the transfer oil cooler is expected to reach approximately 50°C. With the transfer oil cooler installed, the car can remain stable at around 100°C even during continuous driving.