High Transmission Temperature

R J · January 19, 2021

I used my 2020 Silverado Trail Boss 5.3 with the 6 speed transmission to tow my travel trailer. The transmission temperature was usually under 200 degrees even when going up an incline. The temperature got up to 239 degrees when backing up the trailer (we had a small corner spot and it took us 15 minutes to get it situated). I noticed that the transmission temperature gets around 210-215 degrees when driving in stop and go traffic. Is hitting 215-230 degrees too high when towing? Has anyone added an external transmission cooler? Would changing out the transmission fluid to something better help with keeping the temperature low?

davidr83 · January 19, 2021

Does your truck have an external cooler? Back when I had my 2013 Denali, that also had the 6-speed, I put a TRU-Cool 40k cooler in place of the stock external cooler and my trans temps were usually in the 150-160 range during south Texas summer heat. Would go up to 180s when I was laying into it. The stock cooler was normally 180s with easy driving. Did the same mod to my 2008 Sierra that had 4l60/2800 stall and saw similar results. Both trucks had power adders too.

There's a lengthy discussion about it here. https://www.performancetrucks.net/forums/gm-drivetrain-suspension-22/tru-cool-40k-gvw-transmission-cooler-install-thread-470284/page32/

Edited January 19, 2021 by dram1983361
link added

redwngr · January 19, 2021

I don't think you have anything to worry about.

The transmission oil was warmer when parking because the torque converter would have been slipping making more heat that it does when at steady speed on highway, but there would have little or airflow thru the oil cooler.

The computer is monitoring all the sensors that are installed.

It WILL give a warning if/when it thinks the temperature is to high, and may even go to reduced power until it cools some - because it wants to 'self-protect'.

BlancoSilverado · January 19, 2021

18 hours ago, R J said:

I used my 2020 Silverado Trail Boss 5.3 with the 6 speed transmission to tow my travel trailer. The transmission temperature was usually under 200 degrees even when going up an incline. The temperature got up to 239 degrees when backing up the trailer (we had a small corner spot and it took us 15 minutes to get it situated). I noticed that the transmission temperature gets around 210-215 degrees when driving in stop and go traffic. Is hitting 215-230 degrees too high when towing? Has anyone added an external transmission cooler? Would changing out the transmission fluid to something better help with keeping the temperature low?

I not 100% sure but i though all 2020 trail bosses came with 5.3L 10 speeds not 6 speeds the WT truck was the only truck with the 6speed?

This does not answer your question, from what i heard from multiple videos from transmission shops and online writeups, if you keep it under 230F you are fine, above that you might want to do a pan drop to "refresh" the fluid that might of burnt up. If you start running 215-230 for towing a "light" trailer, you should add a trans cooler.

blckblt · January 20, 2021

13 hours ago, BlancoSilverado said:

I not 100% sure but i though all 2020 trail bosses came with 5.3L 10 speeds not 6 speeds the WT truck was the only truck with the 6speed?

This does not answer your question, from what i heard from multiple videos from transmission shops and online writeups, if you keep it under 230F you are fine, above that you might want to do a pan drop to "refresh" the fluid that might of burnt up. If you start running 215-230 for towing a "light" trailer, you should add a trans cooler.

He has a custom TB. The 5.3 in that trim gets a 6 speed.

BlancoSilverado · January 20, 2021

5 hours ago, blckblt said:

He has a custom TB. The 5.3 in that trim gets a 6 speed.

Yup, i was thinking for some reason i read LT TrailBoss

thanks,

Edited January 20, 2021 by BlancoSilverado

CamGTP · January 21, 2021

Going in reverse with a trailer is just asking for transmission temps to sky rocket. Especially if you are trying to back up a small incline or hill, all it's doing is slipping the converter and that heat is being put directly into the fluid.

Grumpy Bear · January 21, 2021

On 1/18/2021 at 10:52 PM, R J said:

I used my 2020 Silverado Trail Boss 5.3 with the 6 speed transmission to tow my travel trailer. The transmission temperature was usually under 200 degrees even when going up an incline. The temperature got up to 239 degrees when backing up the trailer (we had a small corner spot and it took us 15 minutes to get it situated). I noticed that the transmission temperature gets around 210-215 degrees when driving in stop and go traffic. Is hitting 215-230 degrees too high when towing? Has anyone added an external transmission cooler? Would changing out the transmission fluid to something better help with keeping the temperature low?

Transmission thermostat delete before doing a cooler or you will be in the same place you are now. That alone will drop temps 40 to 50 degrees. After the delete mine runs 160 F on a 100 F day. But even that won't help when road speed is near zero and you are working the converter that hard. In that case I'd look into a secondary cooler with a temperature controlled fan.

https://derale.com/product-footer/fluid-coolers/thermostats-1/remote-mount-in-line-thermostats/13021-detail

Snoop around on this site.

Factory fill fluid is a Group III synthetic. Varnish will start to form around 220-225 F and no matter what fluid you have in it the seals start to harden at 240 F. Give them long enough at that temperature and they will slowly turn to cement.

Red Line D6 or AMSOIL ATF is a PAO/POE blend that will take the fluid limit to 275 F or so. Well past the damage point.

When you're running down the road with the converter locked up the converter and pan temps (DIC) are near identical. Under load, like backing up, at a walking speed they converter fluid temperature can be 100 F higher than the DIC display.

Yea, yea, the warning light doesn't come on till about 260 and the limp mode a bit higher. That doesn't mean it's okay to let it rip there. Means you're in trouble and get your foot out of it and find out what's what. It's also the pan temp not the converter fluid temp.

redwngr · January 21, 2021

Big difference between running all day every day at 240 and touching 240 on rare occasion.

Grumpy Bear · January 21, 2021

6 hours ago, redwngr said:

Big difference between running all day every day at 240 and touching 240 on rare occasion.

Absolutely true and why I wrote the below quote to make that exact distinction:

9 hours ago, Grumpy Bear said:

the seals start to harden at 240 F. Give them long enough at that temperature and they will slowly turn to cement.

I can only dumb it down so far.

That said I've never heard ANY trans shop outside GM think running bulk temperatures over 180 F was a good thing.

Most of the damage done by heat happens to parts not the fluids.

Seals, clutch material, clutch bonding, steel plate warp.

Films in the TCEM

The TCM which is submersed in ATF.

Electronics in HOT oil. Great Job GM!!

Before I did the delete on my 6L80E the fluid temperature on a summer day ran 210-230 F all day, every day.

And I wasn't towing anything nor do I live in the desert.

Yes I installed a new thermostat BEFORE deleting it.

If your already at 210-230 F and loading up the converter that fluid in the converter can be over 300 F.