GSEREP111

Hello all!
I just did my 3rd transmission fluid drain and fill ony 2013 GS350. I'm at 87,000 miles, and everything works great.

I'm curious about the normal operating fluid temperature while driving. I plugged in my scanner and drove the 20 miles to work. I was surprised to discover that the temperature was between 190 to 200 degrees F while driving on a flat level freeway at 70 mph.

This seems excessive to me. I have looked for cooler lines going to the radiator, and there are none. I've come to discover that engine cooling fluid helps to warm up cool transmission fluid through a heat exchanger at the rearbof the transmission. On my earlier 1999 GS400's, I installed transmission coolers near the radiator. I'm sure my fluid was 50 to 60 degrees cooler than the car I have now.

Does anyone know how our trans fluid is being cooled? Is 200 degrees an acceptable temperature or am I going to
​have problems? Where is the transmission cooler located?

Thank you all in advance....

bclexus

Your transmission fluid temperature of 190° to 200°F is perfectly fine and within the normal operating temperature range of automatic transmissions nowadays. While the normal operating temperature of engine oil is 212°F (100°C), the transmission fluid typically operates about 15° to 20°F cooler.

You should see transmission fluid cooling lines entering and exiting out of the bottom portion of the radiator where the two smaller fittings are located on the image below.

GSEREP111

Hello and THANKS for your response. I don't see any lines going to the radiator. I look every time I have the car up on the rack. I believe we have a thermostatic valve to control flow in and out of the transmission to the heat exchanger. The exchanger has engine coolant coming in on one part of it, and transmission fluid coming in on the other. They pass each other but don't mix. It helps the transmission warm up quicker, but normally runs hotter than I'm used to. Good thing the WS transmission fluid is synthetic, because normal fluid starts breaking down around 240 degrees

I'd love to add a trans cooler up by the radiator, but it doesn't seem possible.

Thanks for your comments.