Having problems with tranny temp. Just rebuilt and on the freeway temps range from 135 to 190 degrees read at the cooler output on the tranny (outlet at the center of tranny). The over temp light has come on at 180 to 190 degrees. I pull over and shut off the engine and turn it back on and the light goes out for 10 to 40 miles. Don't know if it is actually over heating or a bad sensor. Tranny shifts and runs really smooth, no problems there.

 

Is the torque converter locking up and staying locked up?
Try running it with O/D deactivated and see if it still overheats.

 

The original torque converter wasn't locking up, but I changed it out with a new one and now it is defiantly locking up.
it now only gets to 180 degrees after running on the freeway and then coming to stop. but it comes down in a few min. running on the freeway it runs between 140 and 170, but the light still comes on and i have to shut the engine of and the restart to reset it.

 

According to the factory service manual normal operating temp for the a340h is between 158- and 176 F. So I would say that your temps are normal and something is wrong with your temp sensor.

 

Thanks that is what I needed to know. So intermittent high temps at higher speeds are to be expected and I think I will change the sensor out.

 

The only thing I don't understand is how Toyota expects to achieve a temp range bellow 176 degrees when they are routeing the fluid to be cooled through a radiator cooler where the water temp is already 180 degrees. It seems to me the fluid would always be 180 or higher.
Just food for thought!!!

 

Well, the coolant is cooler by the time it hits the bottom of the rad, but you do have a point.

 

It does seem to make sense to me to that's why I put my cooler with fan after the rad cooler, sort of a pre-cooler. I do see a 10 degree drop in the fluid leaving the tranny to the cooler with cooler and fan on.