I have a 2000 discovery 2 gas V8. The other day after driving for about 10 minutes my transmission overheat light came on so I pulled over and let the car cool down. I got back home and check my ATF and gearbox oil and they were both good. I assumed it was the transmission filter because I haven't changed it in the five years I've owned the car so I drain the ATF and replaced the filter even though they both looked pretty clean still. I took it for a test drive and the light comes on and goes off intermittently as I'm cruising. I've checked the fins in the radiator and they aren't clogged and my fans are both working. I unplugged the front temperature sensor with the light on and it turned off so I'm guessing that is the sensor that is detecting the overheat but I'm not sure if it's an actual issue or just a problem with the sensor. I was thinking if the sensor was bad the light would just be staying on but I'm not too sure. Is there a way to check it with a voltmeter? Or do you have suggestions on what I need to look for or replace? I dont want to throw a new sensor on it of thats not the issue. thank you so much for your time.

 

check your transfer case.

 

that was one of the original things I checked in the fluid was good. I wrote it as gearbox in my original post by mistake

 

Mine does the exact same thing yours does but I've come to the conclusion my sensor is bad i start the car drive about 3 miles and the light flickers on and off until it finally stays on fluids also looked and smelled fine sometimes when I turn on the car the trans overheat light is already on unplugging the front sensor also turns off my light

 

There is a temp sensor in the trans cooler , plug is at the top of the radiator, unplug it and if the light goes out you have a bad sensor. If that one doesn't turn the light out disconnect the one in the tcase. If it comes on even when it the truck is cold you have a bad sensor.

 

My sensor in the trans cooler lit my light, I took it out and put a real gage sending unit in to verify.

 

I never comes on when the truck is immediately called but after about 10 minutes of driving I will come on then go back off again intermittently. If the sensor is bad will the light just stay on or go on and off like mine is

 

Could be either. I don't remember off the top of my head but the RAVE has the temp that it is supposed to come on, you can check with an IR temp gun but it is common for the sensors to go out.

 

where is the best place to get a read on the temp ? Just on the outside of the atf pan?

 

IIRC it's in the neighborhood of 350-400F