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Transmission Thermostat Delete Pros vs. Cons

Eddie 70

By Eddie 70
in Engines & Drivetrain

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11bravoZ71
11bravoZ71

Results are in    STL010 average open highwaytemp is 140 Heavy city use  is up to 197f  stays at around 197 if I idle for an extended period    flipped stock thermos

silveradosid
silveradosid

i did the flip on the weekend, i have 120k miles on my transmission. it was 82 f outside and i drove 80 mph for 30 miles and the temp stayed at 156. before it was always above 200. when it was above 2

14burrito
14burrito

Little 5 quarts ATF rejuvenation followed with the new ATF thermostat being installed. Curious to see if driveability will change at all and interested to see how ATF temps are altered.

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BlaineBug Enthusiast

BlaineBug

Posted
Posted (edited)
2 minutes ago, mikeyk101 said:

That looks like it's the one you want. Now get it installed...

Soon enough.

 

What's the deal with this thermostat with the dual springs and all?  Have not seen that before, although the only cars I have replaced thermostats in were old school.  Seems to be a thing that never needs replacing anymore.  Although maybe some of the things I did as a teen were unnecessary - such as drop-in washable K&N air filters too "for extra horsepowers."

Edited by BlaineBug
BlaineBug Enthusiast

BlaineBug

Posted
Posted

To report after more than a few days of use, I'll say that visually and using the coolant temp gauge on the dash, there is definitely no "noticeable" difference that is significant in regards to the operating temp of the vehicle which always seems to be just slightly to the left (lower than) 210' Fahrenheit.

 

If you're looking to lower transmission temperatures obviously your best route is either bypassing/[plugging the factory thermostatic properties if you live in a warm climate or installing the newer revised lower opening temperature thermostat for the transmission cooler lines if you live in a cold climate and still require low-end transmission fluid temperature moderation.

 

As has been my belief for decades now, a coolant thermostat will not lower temperatures because the thermal output of the motor and the cooling properties of the radiator will always be consistent, and once the thermostat is fully opened, it's essentially taken out of the equation regardless.

 

The new versus old coolant thermostat opening temperatures of 194' versus 207' aren't significant either, a 13 degree difference, with no noticeable change in operating temperature as per DIC gauge cluster.

 

However, installing the revised transmission cooler thermostat will see noticeable improvement of 30-40 degrees Farenheit on average.  Which leads me to believe that typically with no undue stress, hard acceleration, or towing, the transmission was being kept HOTTER on purpose than it's true default operating temperature with the factory transmission fluid cooler thermostat.

 

The engines however are probably designed to be run around 200-210 as they have been for decades.  Even in the 1990s engines were designed to run optimally somewhere between 190-210 degrees Fahrenheit.  And apparently they still do, if not slightly hotter.

Installing a coolant thermostat that opens EARLIER will not result in a cooler operating temperature at all.  An engine produces a whole hell of a lot of heat regardless due to the combustion process and friction as well.  A transmission only puts out heat due to friction, so when you're sailing along smoothly and not constantly accelerating and shifting through the gears (slipping = friction) you will see lower operating temperatures during this time of reduced operational stress.

mikeyk101 Senior Enthusiast

mikeyk101

Posted
Posted

You cannot compare the dash coolant gauge with the transmission temperature display. I have repeated this in many threads and others have posted this as well. The transmission temp display is an active display of current transmission temperatures. However, the coolant gauge does not show the exact coolant temperatures. It will move up to the displayed 210⁰ temperature when's everything is normal. It will show/display 210⁰ when actual coolant temps are anywhere from about 185⁰ to about 225⁰. That gauge is fairly worthless. The only way to know your actual coolant temperature is to use one of those OBD2 readers and an app like torque pro on your phone. I can guarantee that by switching from the 207⁰ to the 194⁰ coolant thermostat that you coolant is in fact running cooler. You are only fooling yourself if you are using the dash coolant gauge to judge whether the 194⁰ is actually helping your coolant to run at a cooler temperature. It is indeed helping. That gauge is one of the least accurate ways to measure this. 

mikeyk101 Senior Enthusiast

mikeyk101

Posted
Posted

And just to add, I can show you proof that using a 194⁰ coolant thermostat over a 207⁰ thermostat does in fact help the coolant to run cooler. 

Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
3 hours ago, BlaineBug said:

As has been my belief for decades now, a coolant thermostat will not lower temperatures because the thermal output of the motor and the cooling properties of the radiator will always be consistent, and once the thermostat is fully opened, it's essentially taken out of the equation regardless.

 

This is a good photo of what Mike is talking about. I run a Reisch Racing 170 F thermostat in a IPSCO holder. This is 37 degrees cooler than the factory 207F stat ran as you can see in the Scan Gauge II display running from the OBDII port. 

 

Now look at the dash gauge. Just a bit below 210 F. that is, 37 F moved it less than one graduation. By the ECU that 160F mark on the dash gauge is actually about 100F. That gauge is not much better than an idiot-lite. 

 

image.thumb.jpeg.fec6e4e8429f6a7e4f08cd66d0fc16e4.jpeg

 

Blain, I don't know what your trans cooling set up is for that year but if the ATF does not run through the radiator, the water temp has no effect on ATF temperature. But lowering the water stat will lower both the water temperature and the oil temperature. 

 

And no, I don't have some larger radiator installed nor do I overdrive the pump. 

  • Like 1
Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
4 hours ago, BlaineBug said:

Installing a coolant thermostat that opens EARLIER will not result in a cooler operating temperature at all.

 

From -25F to +94F my water temperature runs a base 173F. The cracking temperature of the thermostat is 170F and it is fully open by 190F. Pretty typical spread. It can maintain this 'throttling' temperature from the coldest day barely cracked open to a 94F day when it is fully open. It's what a thermostat does. Maintain a 'throttled' temperature. That is, until it can't which is anytime the motor is generating more heat than the radiator can dissipate and how much that is depends on air temperature and air flow. It's a dynamic system.

 

In this photo at 55 mph in a dead wind on level ground the motor is only putting up 30 horsepower of the 305 horsepower it can generate. The radiator has capacity to run much colder if a low stat is in play when only 30 base hp is being generated. 😉 

 

As an aside. Never think your oil temperature is constant just because the motor is water cooled. I hear that allot from guys. I can drop this to third gear and leave in cruise control and run that oil temp up past 250F in minutes. 🤫

 

image.thumb.jpeg.fec6e4e8429f6a7e4f08cd66d0fc16e4.jpeg

BlaineBug Enthusiast

BlaineBug

Posted
Posted
8 hours ago, Grumpy Bear said:

Blain, I don't know what your trans cooling set up is for that year but if the ATF does not run through the radiator, the water temp has no effect on ATF temperature. But lowering the water stat will lower both the water temperature and the oil temperature.

 

Was mentioning 2 different "thermostats" here, the transmission cooler bypass and the engine coolant thermostat.  This discussion now includes 2 different mechanicals.

Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
16 minutes ago, BlaineBug said:

 

Was mentioning 2 different "thermostats" here, the transmission cooler bypass and the engine coolant thermostat.  This discussion now includes 2 different mechanicals.

 

Yes sir, I got that. But water temperature can only have an effect on the transmission if the ATF cooling strategy includes the radiator, right? I believe in yours that has been bypassed by the factory so that you only have the air-to-air exchanger in front of the radiator. 

 

The thermostat on the transmission can only stay in control IF there is enough cooler for the most load it will see. And for most light duty work in 'normal' temperatures it is with surplus. It's why we see a 30 to 60 degree drop in temps under daily driving when switching to the 70C TBV. But load it hard enough of give it a hot enough day with the factory cooler and yea....as you said.... once it's fully opened all bets are off. This is what I was showing in the graphs several pages back. 

BlaineBug Enthusiast

BlaineBug

Posted
Posted
4 minutes ago, Grumpy Bear said:

 

Yes sir, I got that. But water temperature can only have an effect on the transmission if the ATF cooling strategy includes the radiator, right? I believe in yours that has been bypassed by the factory so that you only have the air-to-air exchanger in front of the radiator. 

 

The thermostat on the transmission can only stay in control IF there is enough cooler for the most load it will see. And for most light duty work in 'normal' temperatures it is with surplus. It's why we see a 30 to 60 degree drop in temps under daily driving when switching to the 70C TBV. But load it hard enough of give it a hot enough day with the factory cooler and yea....as you said.... once it's fully opened all bets are off. This is what I was showing in the graphs several pages back. 

I'm not sure what setup it has for cooler routing.  At any rate I'll check my scan tool for water temperatures.

 

I noticed your ScanGaugeII displays "water temp" AND "engine operating temp"?  Where is the second reading taken?

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