When I drive my 4runner on the interstate above 70 mph for more than 30 or so minutes the AT oil temp light comes on. If I pull over and let it idle until it goes off and then keep it below 70 it doesn’t come back on, but as soon as I drive over 70 for very long it comes on. I had the transmission flushed, and this didn’t solve the problem. It’s been doing this for over a year now, but since I rarely take it on the interstate I haven’t worried too much about it.
Your transmission pipes it’s fluid to a cooling coil inside your radiator, the same radiator that cools the engine, to cool the fluid. Your radiator is clearly not up to the task.
You’ll need to verify that fluid is indeed cycling thorugh the radiator, and replace it if necessary.
Okay, I can see that may be the issue, but if you read my post it only happens when I drive over 70 mph for awhile, not when I’m driving uphill or when it’s over 100 degrees outside or anything else that seems like it might cause the light to come one.
Your light is only coming at 70 but damage can be happening before, get it fixed its a lot cheaper than new trans!
Maybe the transmission is in the early stages of slipping and the fluid is overheating because of that.
How is the engine temperature? An engine rutting hotter than normal at highway speeds could also overheat the fluid.