Transmission Thermostat Delete Pros vs. Cons

flyingfool · September 24, 2020

just think of it as an opportunity to install a bigger cam, 6.2 manifold and a 6.2 throttle body! : ) its all fun

Edited September 24, 2020 by flyingfool

Ltz4 me? · September 24, 2020

No time for that, I just want a viable truck in the end...

14burrito · September 28, 2020

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.

Edited September 28, 2020 by 14burrito

14burrito · September 29, 2020

To start off, the thermostat on the 6-speed is stamped 180F.

Same 32mile/45min drive into work, amb temps within a couple degrees F (70/72F):

Pre 5 quart / t-stat flip - 183F once getting to work (WOT pull up to 65mph, slow, parked and idled for a few minutes)

Post 5 quart / t-stat flip - 153F once getting to work (same pull into work cycle as above)

Same 32mile/45min drive home, amb temps within a few degrees F (100F / 105F):

Pre 5 quart / t-stat flip - 192F once pulling into my driveway, parked and idling for 10 seconds or so.

Post 5 quart / t-stat flip – 176F once pulling into my driveway, parked and idling for 10 seconds or so.

After getting home, engine off for maybe 30min, I went back out for errands (105F amb temp). ATF temps during this time were maintained about 180F + a few degree variant from being static or in motion. Similar conditions previously would place me mid 190s + a few degrees again based off static/in motion.

My wife did her 25mile/30min drive into work this morning, ATF reached 140F with amb temps low 70s.

Personally, I did not notice any change in driveability. I perceived my shift quality and power development/shift points were same prior/post. My lambda was/is showing consistent a 1.000 prior to and after the pill flip.

Necessary info to add: we have active grill shutters on our vehicle. With the info/temps posted above, the shutters are open when idling or accelerating up to 30mph, closed at speeds above 30mph and remain closed when decelerating to a stop.

Edited October 20, 2020 by 14burrito

dwchapmanjr · September 29, 2020

4 hours ago, 14burrito said:

Personally, I did not notice any change in driveability. I perceived my shift quality and power development/shift points were same prior/post. My lambda was/is showing consistent a 1.000 prior to and after the pill flip.

I'd be really curious over time how your shift adapts adjust. Interestingly I had my truck in for low temp. It ended up being the harness to my surprise. I thought it was a bad thermostat but they also did a fast relearn. I'm not sure if it common after a fluid flush or because my shift adapts would have learned at a different temperature than expected.

Entirely possible such a small temp difference doesn't really matter but it would be interesting to hear from a GM engineer why they want the temps so high.

14burrito · September 29, 2020

1 hour ago, dwchapmanjr said:

I'd be really curious over time how your shift adapts adjust. Interestingly I had my truck in for low temp. It ended up being the harness to my surprise. I thought it was a bad thermostat but they also did a fast relearn. I'm not sure if it common after a fluid flush or because my shift adapts would have learned at a different temperature than expected.

Entirely possible such a small temp difference doesn't really matter but it would be interesting to hear from a GM engineer why they want the temps so high.

Toyota programmed the Tundras to hold gears longer during to heat the ATF quicker (from what I have read). I pinned the thermostat on the truck, it holds gears longer and for a greater distance from cold drive off. I was able to tell the difference immediately.

I prefer elevated shift points vs the quick upshifts myself which is why I find myself using the tow/haul feature frequently in that truck.

I'll be curious how the Tahoe characteristics change now with cooler temps around the corner.

Forgot to add, my Katech 174F t-stat just shipped today so I am not sure how many miles I'll actually have on the pill flip itself.

Edited September 29, 2020 by 14burrito

Grumpy Bear · September 30, 2020

11/17/2017 I changed the filter and started the conversion to Red Line D6 PAO/POE fluid. Added the 8 quart PLM pan.

3/30/2018 at just under 60,000 miles I did the pill flip and realized a 50 degree drop on AFT temperatures. The pill in mine was stamped 192 F. It NEVER opened in the winter if the trip was under 100 miles and it NEVER throttled below 210 F EVER in the summer. I don't tow, I don't haul. It now runs cooler in the summer and warmer in the winter. Like automatics have for over 60 years.

9/29/2020 I now have 130,000 miles on the truck and have posted the temperature charts so many times with various water stats I'm running out of room to do so. Now 95.5% Red Line fluid.

The difference it all made to shift quality, shift timing, shift speed, shift rpm is ZERO. But then I didn't do this modification for those reasons. Those are software/hardware issues.

I did it to prolong drivetrain life and increase fuel efficiency.

So far....so good.

:thumbs:

Every few months I post this material and update it on my build site often enough. What changes is I continue to rack up the miles without issue while those I write these responses for continue to 'study' the 'problem'.

On 7/30/2020 at 5:08 PM, CamGTP said:

No cons here, did exactly what is needed.

We are just making it like the 6L80e's in the previous body trucks, they never had a thermostat in those and never had problems. There is another thread going on about this today too.

Cameron twist wrenches for a living and this was the FIRST reply to this thread and yet.......we continue to 'study' the 'problem'.

Why is that?

:wtf:

silveradosid · October 1, 2020

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 200 my transmission would not shift until i was at 2500 rpms until it cooled down to 180. now it shifts the same no matter how i drive the truck. should have done this sooner

14burrito · October 20, 2020

On 10/1/2020 at 5:22 AM, silveradosid said:

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 200 my transmission would not shift until i was at 2500 rpms until it cooled down to 180. now it shifts the same no matter how i drive the truck. should have done this sooner

Glad to hear you had a positive experience from the pill flip!

Curious, does your platform have the "active grill shutters" or not?

silveradosid · October 20, 2020

No it is a 2014 so no shutters

14burrito · October 20, 2020

1 hour ago, silveradosid said:

No it is a 2014 so no shutters

Thank you for the follow-up.

Was curious only for anyone who may reference this in the future and using it to compare ATF temps.

Trouble_shooting · November 8, 2020

Thank you to Grumpy Bear, CamGTP and OP for starting this thread. After reading this thread and a little further investigation I did the “flip” this morning.
The trans. warms up quicker and maintains a much more modest temp. Drove 50 miles in 70* temp. freeway 70mph. Temp never went above 155*.

Running 33.5” tires, at freeway speeds it would always run just below 200*. 2019 LD

Schwab7767 · May 28, 2021

Story: transmission overheated @ 60k miles. Warranty replaced with new transmission. I’ve had the vehicle (2018 suburban LT 4x4) since new and always sit around 190 degrees give or take and back and fourth around 200 when towing. With the new transmission I keep hitting 210 up to 220 driving around town and not driving hard. I haven’t towed yet but tow often and I am very concerned and afraid to tow. I just finished a thermostat delete to test that out and driving for about 30 min around town and freeway it was over 190 and climbing. It took a while to get there compared to normal but still got hot. Dealership has no clue and the transmission shop has no clue. I need help in figuring out what could be causing the heat. I am so for an oil change and my AC blow nice and cold. Story: transmission overheated @ 60k miles. Warranty replaced with new transmission. I’ve had the vehicle (2018 suburban LT 4x4) since new and always sit around 190 degrees give or take and back and fourth around 200 when towing. With the new transmission I keep hitting 210 up to 220 driving around town and not driving hard. I haven’t towed yet but tow often and I am very concerned and afraid to tow. I just finished a thermostat delete to test that out and driving for about 30 min around town and freeway it was over 190 and climbing. It took a while to get there compared to normal but still got hot. Dealership has no clue and the transmission shop has no clue. I need help in figuring out what could be causing the heat. I am so for an oil change and my AC blow nice and cold.

Mike1950 · July 6, 2021

I have a 2016 Suburban 6 speed - 98% highway miles. I love this truck- it’s been to 42 states. Torque converter blew at 84000 miles. Luckily had 100,000 mile extended warranty. Temp ran 190-210. Did the “pill flip” under the trans thermostat. Now runs 147-160. Maybe 170 towing or on long mountain climbs out west. Since the next trans will be on me I hope this will help the trans life. Wish someone would come up with a 160 degree thermostat as a fix. I haven’t noticed any change in performance, fuel economy, or shifting. Heat has always been a killer of transmissions. Would love to know GM’s reason for this.

Edited July 6, 2021 by Mike1950

truckguy82 · July 9, 2021

On 5/27/2021 at 9:36 PM, Schwab7767 said:

Story: transmission overheated @ 60k miles. Warranty replaced with new transmission. I’ve had the vehicle (2018 suburban LT 4x4) since new and always sit around 190 degrees give or take and back and fourth around 200 when towing. With the new transmission I keep hitting 210 up to 220 driving around town and not driving hard. I haven’t towed yet but tow often and I am very concerned and afraid to tow. I just finished a thermostat delete to test that out and driving for about 30 min around town and freeway it was over 190 and climbing. It took a while to get there compared to normal but still got hot. Dealership has no clue and the transmission shop has no clue. I need help in figuring out what could be causing the heat. I am so for an oil change and my AC blow nice and cold. Story: transmission overheated @ 60k miles. Warranty replaced with new transmission. I’ve had the vehicle (2018 suburban LT 4x4) since new and always sit around 190 degrees give or take and back and fourth around 200 when towing. With the new transmission I keep hitting 210 up to 220 driving around town and not driving hard. I haven’t towed yet but tow often and I am very concerned and afraid to tow. I just finished a thermostat delete to test that out and driving for about 30 min around town and freeway it was over 190 and climbing. It took a while to get there compared to normal but still got hot. Dealership has no clue and the transmission shop has no clue. I need help in figuring out what could be causing the heat. I am so for an oil change and my AC blow nice and cold.

Those were pretty much exactly my temps when my trans thermostat was non functional and stuck closed. I had to figure it out myself, dealer was clueless.

Might want to verify your trans cooler is receiving flow. You can do this warming up your trans and feeling the output line from the trans cooler. If you’re actually flowing fluid through it, it should very hot. Like burn you if you keep your hand on it. You can also touch the lines coming from the tstat as one is supply and one is return to the cooler, with your trans hot, both lines should be very hot to the touch. If you’re not receiving flow, one will be ambient temp.