Transmission Thermostat Delete Pros vs. Cons

Grumpy Bear · December 19, 2022

10 hours ago, PowerDr said:

Does anyone know if installing the new T-stat from the TSB with the "70" stamped on it would void an extended warranty? I have a 2019 with 42,000 miles on it. I have an extended warranty up to 82,000 miles. I would like to install the new TSB T-stat but I don't want to have an issue with the warranty if I have tranny troubles down the road.

Thanks

No issue.

ousooner74 · August 21, 2023

Have a 2016 GMC Sierra 1500 with the 6L80E (6-speed) transmission), had a new/rebuilt transmission installed about 6 months ago. Anyway, here in Oklahoma and trans temps average around 195 degrees in the summer but when towing they increase significally, was thinking about adding an external trans cooler but now wondering if I just need to replace this thermostat with the cooler one? Thoughts?

mikeyk101 · August 21, 2023

3 hours ago, ousooner74 said:

Have a 2016 GMC Sierra 1500 with the 6L80E (6-speed) transmission), had a new/rebuilt transmission installed about 6 months ago. Anyway, here in Oklahoma and trans temps average around 195 degrees in the summer but when towing they increase significally, was thinking about adding an external trans cooler but now wondering if I just need to replace this thermostat with the cooler one? Thoughts?

The cheapest thing you can try is the new thermostat. It's still going to increase a bit when towing but should stay in a better range. What are you towing? I have towed my 25' toyhauler both without the new trans thermostat and with the new thermostat and did notice a difference for the better.

BlaineBug · August 21, 2023

Just now, mikeyk101 said:

The cheapest thing you can try is the new thermostat. It's still going to increase a bit when towing but should stay in a better range. What are you towing? I have towed my 25' toyhauler both without the new trans thermostat and with the new thermostat and did notice a difference for the better.

I have noted that in heavy traffic in summer heat, my transmission may still reach 180-190 degrees, so my initial reports may have been lower. But still, typically transmission temperatures are 140-150 max unless special circumstances exist.

Grumpy Bear · August 22, 2023

6 hours ago, BlaineBug said:

I have noted that in heavy traffic in summer heat, my transmission may still reach 180-190 degrees, so my initial reports may have been lower. But still, typically transmission temperatures are 140-150 max unless special circumstances exist.

Slow traffic = no air. No air = more heat. Mine reacts identically to yours. I suppose a temperature triggered aux cooler with a fan might be center stage next.

ousooner74 · August 24, 2023

On 8/21/2023 at 4:49 PM, mikeyk101 said:

The cheapest thing you can try is the new thermostat. It's still going to increase a bit when towing but should stay in a better range. What are you towing? I have towed my 25' toyhauler both without the new trans thermostat and with the new thermostat and did notice a difference for the better.

29' bumper pull travel trailer, I am going to add an external cooler and the new thermostat I believe. Just made me real nervous when I started seeing trans temps in the 220's and never got lower than about 196

TheRiver · August 24, 2023

1170 mile drive yesterday...................straight thru, Ocala, FL to norther Illinois/almost Wisconsin. All in this insanely hot/humid weather.

I installed the lower temp tranny thermal bypass unit prolly 2 years ago now as well as installing the Corvette/Camaro engine thermostat on my truck shortly after.

Anyhow; trip home yesterday, trans stayed in the 147-154* range while cruising..............AC on the whole drive home. The trans temp would get up to 167* if I stopped at rest area and either shut truck down, or left it running..............never got any warmer than that....................no air flow. Only time my engine gauge would move would be after these short breaks getting back onto the Interstates. The trans heat that built up had to go somewhere; so it went into the condenser which pushes that heat into the radiator, and the engine coolant temp spikes for a couple minutes until the HOT air going down the highway cools it down enough.

BlaineBug · August 24, 2023

On 8/21/2023 at 10:57 PM, Grumpy Bear said:

Slow traffic = no air. No air = more heat. Mine reacts identically to yours. I suppose a temperature triggered aux cooler with a fan might be center stage next.

The dual electric fan setup seems to be more than sufficient. They really howl when on high speed. Not sure if your 4.3 has the same setup though.

Grumpy Bear · August 24, 2023

Lates Updates

8/24/2023

I continue to collect data on Pepper and the modifications I make to her.

Note: This is a 2015 V6 NON-NHT truck so the ATF cooling is by an exchanger in the radiator COLD tank or passenger side as a standalone cooling system. There is no air to air on this truck. 95F days ATF ran 195 to 225F and higher when stalled in wreck traffic or in the city stop and go.

1.) First enhancement was a more heat tolerant fluid and one with a higher thermal capacity and conductivity. Red Line's D6. That was good for about 5F.

2.) Isolating the best speed for cooling was next. This proved to be 50-55 mph. Runs hotter if speed is more OR less.

3.) Lower water thermostat. Four total tried including the factory 207F, 194F the aftermarket 180F and 170F in a few configurations. This was huge. More so than I thought at the time.

4.) 8-quart PML finned pan. More for ease of fluid changes then heat rejection. What it did do was speed recovery of temperature when it spiked and delayed heat up. Just more fluid to heat and cool and more surface area to work with.

5.) Pill flip came next, and the full effect of the colder water thermostat became apparent. Those would be the orange and blue lines. Total effect was knocking 60F out of steady state fluid temps at 55 mph. HUGE. But it took a long time to heat up in cold weather and used more fuel six months a year. And I lived with that until GM release the 70C TBV.

6.) Install 70C TBV. Warmer in the winter. Throttled nicely in air temperatures between 55F and 77F.

All this revealed the FACT that even with all of this that I still don't have enough cooling to maintain throttling temperatures when ambient exceeds 80F or enough to tow anything and maintain a safe ATF temperature. More cooling is in the works. Exploring a second stage air to air AND the NHT radiator.

So, you may be asking, Jeez Louise how cold do you wish to run it? Cold enough to maintain the throttling the TBV is DESIGNED to provide. Mid 140'sF. During the hardest service I expect to see. I'd also like to see the hot soak temps not to exceed 160F. Right now, that is limited to 55 mph and totally unloaded.

I can measure no impact on MPG over the multiple years I've been running this down. Now off to collect more data. It's a hot one today. Rare opportunity.

(Updated graph a few post down)

Edited August 25, 2023 by Grumpy Bear

BlaineBug · August 24, 2023

53 minutes ago, TheRiver said:

1170 mile drive yesterday...................straight thru, Ocala, FL to norther Illinois/almost Wisconsin. All in this insanely hot/humid weather.

I installed the lower temp tranny thermal bypass unit prolly 2 years ago now as well as installing the Corvette/Camaro engine thermostat on my truck shortly after.

Anyhow; trip home yesterday, trans stayed in the 147-154* range while cruising..............AC on the whole drive home. The trans temp would get up to 167* if I stopped at rest area and either shut truck down, or left it running..............never got any warmer than that....................no air flow. Only time my engine gauge would move would be after these short breaks getting back onto the Interstates. The trans heat that built up had to go somewhere; so it went into the condenser which pushes that heat into the radiator, and the engine coolant temp spikes for a couple minutes until the HOT air going down the highway cools it down enough.

How many degrees earlier does that Camaro/Corvette coolant thermostat open versus the stock thermostat for these trucks?

Grumpy Bear · August 24, 2023

1 minute ago, BlaineBug said:

The dual electric fan setup seems to be more than sufficient. They really howl when on high speed. Not sure if your 4.3 has the same setup though.

It does. We have different goals and setups is all. But yea, a fan screamer when AC full cool and it holds water in my lower thermostat motor about 183F on a 170F cracking temperature. It was pointless with the 207F water thermostat.

mikeyk101 · August 24, 2023

5 hours ago, BlaineBug said:

How many degrees earlier does that Camaro/Corvette coolant thermostat open versus the stock thermostat for these trucks?

It's a GM 194⁰ thermostat instead of the Silverado 207⁰. I installed mine earlier this year after my Motorrad 194⁰ failed me miserably. The Motorrad had only been in for a couple months after my OEM failed after 7 years. I guess this is one of those parts where OEM is the better choice over aftermarket. Since the original served me well for 7 years, I went with another GM one. It did make a difference on mine. And since it's an actual GM part, I'm going to assume that I will get many years of use out of it like the original.

BlaineBug · August 24, 2023

3 minutes ago, mikeyk101 said:

It's a GM 194⁰ thermostat instead of the Silverado 207⁰. I installed mine earlier this year after my Motorrad 194⁰ failed me miserably. The Motorrad had only been in for a couple months after my OEM failed after 7 years. I guess this is one of those parts where OEM is the better choice over aftermarket. Since the original served me well for 7 years, I went with another GM one. It did make a difference on mine. And since it's an actual GM part, I'm going to assume that I will get many years of use out of it like the original.

Just remember that the engine computer is going to be tuned for that 207' thermostat.

mikeyk101 · August 24, 2023

6 minutes ago, BlaineBug said:

Just remember that the engine computer is going to be tuned for that 207' thermostat.

I haven't noticed any issues by going with the lower temp thermostat other than consistently lower temps than I had before. No drivability issues at all. I don't have any tune in mine. I had read that if I went with a drastically lower thermostat that a tune may be needed but this is only 13⁰ less than the stock one. And by getting lower trans temps because of the updated trans cooling thermostat not heating the AC condenser as high as it was and the coolant thermostat opening sooner, I think my truck is happier...

Edited August 24, 2023 by mikeyk101

BlaineBug · August 24, 2023

18 minutes ago, mikeyk101 said:

I haven't noticed any issues by going with the lower temp thermostat other than consistently lower temps than I had before. No drivability issues at all. I don't have any tune in mine. I had read that if I went with a drastically lower thermostat that a tune may be needed but this is only 13⁰ less than the stock one. And by getting lower trans temps because of the updated trans cooling thermostat not heating the AC condenser as high as it was and the coolant thermostat opening sooner, I think my truck is happier...

I have the lower "revised" transmission cooler thermostat as well. I do not believe there is any tuning that would be that specific to the transmission as transmission temperature can vary widely based upon load, towing/not towing, environment, weather, etcetera. However engine temperature is fairly stable regardless of climate or condition. I'd be curious to learn more about tune.

I know my 1995 Jeep Cherokee had a 195 degree thermostat as stock. They are pushing them higher and higher for fuel efficiency.

PS - what is the part number for the lower temperature coolant thermostat for the 5.3?

Edited August 24, 2023 by BlaineBug