Trans temp question
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,704
Likes: 2,625
From: SE Florida
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.
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Fleet Mechanic
Joined: May 2010
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From: West by God Virginyuh
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,704
Likes: 2,625
From: SE Florida
It's 34°F here this morning. It's completely clear, so no snow.
2006 Bullet-Riddled 6.0
Joined: Sep 2011
Posts: 651
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From: Sac River Delta Ca.
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.
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.
What I do know about the transmissions is there are expensive to replace and why I have had both of my 2006 flushed at Ford every 30K instead of drain and fill. Along with the 2008 pan and filter installed. Paranoid... yea maybe a bit.
I know that you were heavily involved with its design so that's that. Thanks..
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,704
Likes: 2,625
From: SE Florida
There are two positions. When closed 10% of the normal flow goes to the coolers. When open 100% goes to the coolers.
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