Default trans temp lightSo I have yet another weird new issue popping up I have a 1999 disco 2 210000 miles its a great running truck. I have bean getting an intermittent trans over temp light all fluids are good and full. Two days ago i was cruising down the interstate at 75 mph and the trans temp light came on after about 20 miles, I kept driving and went to pass a semi and as soon as the truck downshifted and accelerated to about 77 the light flickered and went out as soon as I was around the semi and the truck shifted back up and i slowed to 75 the light flickered and came back on so i messed with it for about 45 miles and continued the same pattern. the next day made the same drive and same thing the light came on after about 20 miles and flickered off every time it downshifted and sped up and flickered off every time it up shifted and slowed to 75????

 

You most likely have a defective trans temp sensor. Replace the one at the transfer case first and see if that fixes it. If that doesn't work you need to replace the sensor on the left side of the radiator. You need to remove the radiator to get to it. If you don't have to remove the radiator good for you. If you can figure out a way to relocate that sensor so you don't have to remove the Radiator next time - even better.

Make sure your transfer case is not overfilled or using super thick Royal Purple gear fluid. That will also make it overheat. Clean your Transfer case and tranny with brake cleaner - zero grease or oil - so the heat dissapates more effectively. Same as a radiator you don't want it covered with grease and oil. Make sure your Transmission cooler is clean and the lines are not clogged. Make sure BOTH have clean fresh fluid.

 

I went after the transmission sensor first. Super easy to get at without removing the radiator for me. Mine ended up staying on, even when the truck was dead cold parked overnight. I've installed a temp gauge for real numbers.
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