So when the radiator loop is closed (cold weather driving), what is maintaining that optimum temp range at the heat exchanger? The engine thermostat maintains temp inside the motor, not inside the radiator where the tranny fluid heat exchanger is located.

 

Pick Pick Pick. Now you are grabbing at straws.
Open loop happens around 95 F coolant temp.

 

Come on dude, be serious. Your "loop" joke is a good one.......or r u being serious?

 

The thermostat indirectly controls it, because the exchanger is going to be as warm as the coolant flowing around it...as for open loop/closed loop, are we talking about fuel system, or cooling system? they are different.

 

Can the thermostat indirectly control optimum tranny fluid temp range? Doesn't seem like it. I think he was joking about the "loop", but I'm not sure.

 

It's incidental. The thermostat controls engine temp, not trans... but the heat it dumps into the radiator can keep the trans from running too cold.
Only has to be 90-100 deg or so to keep the trans happy.

 

Not controlled but influenced/maintained within a range.
Coolant temp in radiator, around the transmission heat exchanger, runs around 150 F in 75F ambient.

 

Bingo.


There's a wide range between, "controls" and "has no effect at all".


That range is where reality lives.

 

So optimum range is probably nonexistent.

 

All I know is that when I had problems running hot (around 220, IR verified), my trans was also running about 218 at the pan. That was before I took the trans loop out of the rad.

 

Not according to Aisin-Warner and Toyota, and Outlaw Star and...

 

If u have the numbers from those 3 sources, share them with us. What is the tranny fluid optimum temp range?

 

IIRC, it's between 125-172℉ give or take five degrees.

 

....but do u have some technical data to support that really wide temp range that u could share with us.

 

My mistake, got kind of side tracked on my post since I'm at work right now but I'm looking for a good source of info.