Transmission fluid temperature in the DIC

Did you know that the Z06 has 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 activated when the transmission temperature exceeds 130°C (266°F) for more than 10 minutes. The trans fluid value can then be selected for viewing in the DIC similar to oil and coolant temperature.

The sensor is a part of the the fluid fill plug in the T56 transmission. 

The high thresholds are also why most owners have never seen the warning, as it will hardly ever happen during normal use. 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.

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 transmission temperature in the DIC afterwards.

The transmission fluid temperature is also available as a parameter through the OBDII/diagnosis interface (it does not require the overtemp warning to be triggered to be available). That way, the transmission temperature can be monitored together with other engine parameters.

If you don't have access to an OBDII adapter or HP Tuners, but still want to monitor the temperature, there's still an option: A simple push button can be wired to the fluid temperature sensor. When the button is pressed, 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 and don't share the same fluid, so for cars driven in hard race conditions, monitoring only the transmission temperature might give a false safety.

*DIC - Driver Information Center.