2000StreetRod
Moderator Emeritus
- Joined
- May 26, 2009
- Messages
- 10,597
- Reaction score
- 334
- City, State
- Greenville, SC
- Year, Model & Trim Level
- 00 Sport FI, 03 Ltd V8
external ATF loop control
Some 5R55E users modify the valve body so the external ATF cooling loop is always open. I think the internal thermostat control is based on sound logic and that rapidly reaching and maintaining 150 deg F has performance and reliability advantages. I found that there is always a small flow thru the external loop but that I have to drive for about 20 minutes before the temperature reaches 150 degrees F and the internal valve opens allowing full flow thru the external loop. That's when shift flares can occur because the pump has to keep up with the additional fluid flow.
I agree that just having a remote filter (ATF or engine oil) located away from the engine and in the moving vehicle airflow reduces the oil temperature. You can even purchase a fin assembly that fits over a filter to radiate additional heat. With the ATF external loop thermostatically controlled by the internal sensor/valve you never have to worry about overcooling the ATF. By the way, liquid to liquid heat exchangers (radiator internal ATF cooler) are more effective than air to liquid heat exchangers (auxiliary ATF coolers).
Some 5R55E users modify the valve body so the external ATF cooling loop is always open. I think the internal thermostat control is based on sound logic and that rapidly reaching and maintaining 150 deg F has performance and reliability advantages. I found that there is always a small flow thru the external loop but that I have to drive for about 20 minutes before the temperature reaches 150 degrees F and the internal valve opens allowing full flow thru the external loop. That's when shift flares can occur because the pump has to keep up with the additional fluid flow.
I agree that just having a remote filter (ATF or engine oil) located away from the engine and in the moving vehicle airflow reduces the oil temperature. You can even purchase a fin assembly that fits over a filter to radiate additional heat. With the ATF external loop thermostatically controlled by the internal sensor/valve you never have to worry about overcooling the ATF. By the way, liquid to liquid heat exchangers (radiator internal ATF cooler) are more effective than air to liquid heat exchangers (auxiliary ATF coolers).