Originally Posted by tfunk88

I agree, but hat seems odd to me is the trans is reaching a higher operating temp when it is super cold out, and when the temp outside is just cold it runs at a lower operating temp. -2 our this morning, trans goes up to 168 then drops to 162. 30 degrees outside on way home and trans doesn’t go over 158.

Originally Posted by Mark Kovalsky

I never noticed that, but that doesn't mean it isn't happening. I don't have an explanation as to why that would happen.

Originally Posted by wedge542

Snows after you mark,better bundle up, none in 28 yrs till now little northwest of you. Orange juice going up already.

Originally Posted by Mark Kovalsky

A thermostat opening is exactly what happened.

There is a thermostat in the transmission. It has a nominal temperature of 165°F to open. Nominal means it's an approximate temperature. Anywhere from about 155-175°F is acceptable.

When the thermostat is closed only a trickle of fluid is sent to the coolers. Almost all of the fluid just recirculates inside the transmission with no cooling. So that trans will warm to normal temps (and 168°F is perfect) in almost any temperature. That's how we designed it.


Why? Because the thermostat is not a digital device. It may open at 162°F one time and 168°F another time. Absolute precision on the opening temperature was not at all important, so no effort was made to make a thermostat that is 100% repeatable.


The thermostat in the 5R110W is a wax pellet, not a metallic. It's the same principle as an engine coolant thermostat.


The stock filter does not work like that. It does not have a thermostat in it. It receives 10% of the cooler line flow at any temperature that there is flow. 90% bypasses the filter. The filtered and non filter fluids are mixed back together and go through the cooler. There is no path for the filter to bypass the coolers.

Originally Posted by mhatlen

May have been thermostat in the transmission decides whats sent off towards the cooler and filter setup?