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Transmission fluid temperature in the DIC

Did you know that the Z06 models have a differential fluid temperature sensor that allows you to read the temperature in the DIC/LCD display)? The reading is not available by default, but is added to the DIC after a "high trans temp" warning, which is triggered when the transmission temperature exceeds 130°C (266°F) for more than 10 minutes. The high thresholds are also why most owners have never seen the warning, as it will hardly ever happen during normal use. After the warning has been triggered, the trans fluid value can be selected for viewing in the DIC as for the oil and coolant temperature.

The sensor is a part of the the fluid fill plug in the T56 transmission. 
During continous heavy load on track days or circuit racing, the warning thresholds are actually too high. The fluid temperature can raise far beyond 130°C before the driver is notified, due to the 10 minute delay. Above 130°C, gear oils starts to break down and lose its viscosity. This can create a viscious circle of increasing friction and temperature, which can lead to bearing and/or gear failure.

Fortunately, the transmission temperature thresholds in the ECM can be changed using HP Tuners or similar software. I've reduced the "Set temp" to 110°C (230°F) and the "Set Time" to 60 seconds. That way, I quickly get an indication when I track the car  and can monitor the transmissio temperature in the DIC afterwards.

The transmission temperature is always available through the OBDII/diagnosis interface, it does not require the overtemp warning to be triggered. That way, the transmission temperature can be monitored together with other engine parameters.

If you don't have access to OBDII adapters or HP Tuners, but still want to monitor the temperature, all is not lost. A simple push button can be wired to the fluid temperature sensor. When you push the button, the low resistance causes the ECM to read a false high value which triggers the overtemp warning.  Afterwards, the temperature can be read in the DIC. Ideally, there should be a resistor in series (R1) with the push button (SW1) to avoid a short circuit current. Start with a high value  and reduce the resistance until the alarm is triggered. The ECM is likely designed to handle a sensor short circuit, but better safe than sorry.

The transmission and the differential are in different casings with separate fluids, so monitoring only the transmission temperature might give a false safety, especially for cars driven hard in race conditions. As a future project, one could install a temp sensor in the differential too, and switch between them using a toggle switch or even an electric circuit which enables the sensor reading the highest value. An additional LED driver output could indicate which sensor is read.