Transmission temp?

[COElkFreak]

Have a 2018 Tahoe I just change the transmission fluid and filter. Just the other day while pulling the boat which is only 18 foot older Bayliner the transmission temp got to 260. Did I do something wrong? Do I need to fill the pill or is the transmission toast?

 

[Marky Dissod]

Have a 2018 Tahoe I just changed the ATF and filter.
Just the other day while pulling the boat which is only 18 foot older Bayliner the ATF got to 260F.
Did I do something wrong? Do I need to flip the pill, or is the transmission toast?

I'm crazy enough to think that EVERY TIME the ATF gets over 239F, the ATF needs to be changed, AGAIN.
No way to know if you did something 'wrong', but you need to 'flip the pill', or do something to keep ATF temps down.
If you get that ATF analyzed, you'll learn for sure if the transmission is in any danger.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

That temperature is high.

@NickTransmissions is our resident transmission expert, and he may be able to provide some pointers to help you in diagnosing the source of your issue.

 

[Trey Hardy]

Have a 2018 Tahoe I just change the transmission fluid and filter. Just the other day while pulling the boat which is only 18 foot older Bayliner the transmission temp got to 260. Did I do something wrong? Do I need to fill the pill or is the transmission toast?

Did you have it in tow haul?
My Tahoe did not like pulling trailers either. Shit my Silverado would get to 220 or so in stop and go traffic. To cure this I invested in a tru cool 40k transmission cooler I think it was around 100-150$ pretty easy install. Got my temps from 220 down to 165-175

 

[Doubeleive]

Have a 2018 Tahoe I just change the transmission fluid and filter. Just the other day while pulling the boat which is only 18 foot older Bayliner the transmission temp got to 260. Did I do something wrong? Do I need to fill the pill or is the transmission toast?

260 may have burnt some fluid
this will replace the oem thermostat and "help" keep it cooler but as others mentioned a tru-cool 40k and maybe even a B&M deep transmission pan will help even more the pan allows for 2 qt's extra fluid and has "fins" for a smidge more air cooling

trans-go-

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B&M pan -

https://www.holley.com/products/drivetrain/transmission_pans_and_accessories/gm/parts/70392?utm_term=&utm_campaign=Google+Shopping+-+B%26M+-+Brand&utm_source=google&utm_medium=cpc&hsa_acc=7848552874&hsa_cam=1734309285&hsa_grp=66859688534&hsa_ad=337963690926&hsa_src=g&hsa_tgt=aud-451086445877:pla-657988151721&hsa_kw=&hsa_mt=&hsa_net=adwords&hsa_ver=3&gad_source=1&gad_campaignid=1734309285&gbraid=0AAAAAD1FzSqWGNBmU-t5aYdZeWxqV1Xa3&gclid=Cj0KCQjwmqPDBhCAARIsADorxIalWfg1IT3IDjl4gw7k8mc3UXS1-w8fkJB0KzC3QOHEpOnjvKKZIYIaAmYhEALw_wcB

 

[COElkFreak]

Yes she had it in Tow haul. I will definitely look into the cooler and changing out the bypass valve.

 

[COElkFreak]

Thanks for all the replies so far. Love he help and always open to more and
more suggestions.

 

[swathdiver]

Thanks for all the replies so far. Love he help and always open to more and
more suggestions.

Do you have 3.08 gears? Does the Tahoe have an external transmission cooler besides the one in the condenser?

Definitely put in the lower temp thermostat or flip the one that's in there. Don't remove it or the fluid will not flow correctly.

Dexron VI is made to take about 400 degrees. The computer system for the 6L80 starts giving warnings when the temp climbs above 260 degrees.

I'd change it again if mine were yours. Normally I wouldn't drop the pan but I'd be curious this time to see if something gave way.

 

[Rygrego]

My 16 was running 209 with no load and then I switched to the new lower temp GM trans thermostat and a Mishimoto trans cooler. My trans temp never exceeds 180 now even when towing my 24 foot tritoon in 115 degree Arizona heat. Best cooling money I've spent.

 

[COElkFreak]

Do you have 3.08 gears? Does the Tahoe have an external transmission cooler besides the one in the condenser?

Definitely put in the lower temp thermostat or flip the one that's in there. Don't remove it or the fluid will not flow correctly.

Dexron VI is made to take about 400 degrees. The computer system for the 6L80 starts giving warnings when the temp climbs above 260 degrees.

I'd change it again if mine were yours. Normally I wouldn't drop the pan but I'd be curious this time to see if something gave way.

Is there an easy to way to tell if it has the external cooler? I’m a Ram Cummins guy so these GMs are kinda new to me.

 

[Doubeleive]

Is there an easy to way to tell if it has the external cooler? I’m a Ram Cummins guy so these GMs are kinda new to me.

the oem cooler goes across the top of the radiator
on my Silverado I installed the tru-cool on page 25, tahoe/yukon/escalade should all be very similar

Black Betty 2018 Z71 Silverado....build

after we got back from dinner found out UPS had came and dropped off the running boards..... well sort of I received 2 running boards not in a box, loose one has a big long scratch on it, there wrapped in plastic and a very thin foam padding, I am assuming UPS ****** up the original box and just...

www.tahoeyukonforum.com

 

[ss4chad]

After I put in a 2800 Circle D stall converter in my truck, I installed a cooler flow bypass kit and a front Trans Cooler. Temps range around 125 - 165 range year round. From ball freezing winters to ass scorching summers!
I put in the Tru-Cool Max Heavy Duty 40,000 GCW Trans Perf Oil Cooler #47391 and the
Superior 6L80 6L90 8L90 10L90 Cooler Flow Bypass Kit #STL010

Money well spent!

Chad

​

 

[PA-WOODCHUCK]

MY 2016 towing 7000lb boat runs about 180* That said how do I check if it has the factory HD package if even offered?

 

[jaywestfall]

After I put in a 2800 Circle D stall converter in my truck, I installed a cooler flow bypass kit and a front Trans Cooler. Temps range around 140 - 180 range year round. From ball freezing winters to ass scorching summers!
I put in the Tru-Cool Max Heavy Duty 40,000 GCW Trans Perf Oil Cooler #47391 and the
Superior 6L80 6L90 8L90 10L90 Cooler Flow Bypass Kit #STL010

Money well spent!

Chad

​

TEXAS!!!!

 

[fozzi58]

There's a bulletin (aka recall) on 15-19 6L80 trans lines. Mine were replaced with the updated ones. Also Circle D 3000 stall torque converter, and I did have the thermostat removed - not flipped. My temps are usually around 165 (no 3rd party cooler). The only time it gets up to the 190's is during autoX events.

In the winter I usually let the trans temp hit 60 before driving off.

 

[COElkFreak]

I’m changing the fluid as we speak and all looks ok. I’m also installing a transmission bypass. Not flipping the bought a new assembly. See how it drives and then if needed I will install the bigger cooler.

 

[tagexpcom]

Have a 2018 Tahoe I just change the transmission fluid and filter. Just the other day while pulling the boat which is only 18 foot older Bayliner the transmission temp got to 260. Did I do something wrong? Do I need to fill the pill or is the transmission toast?

I'm no expert but curious - how long (time or miles) was it at 260F? Also, what as the ambient - can you avoid afternoons and tow in morning / night (cooler temps) till you get a solution?

From reading many posts - 260F is not necessarily so hot as being immediately fatal to the transmission for a short period but rather the 'immediate' issue is it breaks down the transmission fluid requiring fluid change or.... the bad fluid could lead to damage. Agree it's not good to let this occur regularly or for long length of time. I offer this comment to possibly lighten the worry if it's helpful

Agree with adding a cooler comments - looking forward to reading about what you do.

 

[COElkFreak]

I'm no expert but curious - how long (time or miles) was it at 260F? Also, what as the ambient - can you avoid afternoons and tow in morning / night (cooler temps) till you get a solution?

From reading many posts - 260F is not necessarily so hot as being immediately fatal to the transmission for a short period but rather the 'immediate' issue is it breaks down the transmission fluid requiring fluid change or.... the bad fluid could lead to damage. Agree it's not good to let this occur regularly or for long length of time. I offer this comment to possibly lighten the worry if it's helpful

Agree with adding a cooler comments - looking forward to reading about what you do.

It was pretty warm outside maybe around 93 degrees. She was just headed to lake after work for the long weekend. I was not with her but it hit 260 for 20 miles or so. She turned on the heater which helped bring it to 250.

I do also question why GM runs a 207 degree thermostat in these trucks as well. My Ram runs a 195.

 

[Marky Dissod]

I do also question why GM runs a 207F thermostat in these trucks as well.

Once you wrap your mind around the influence that CAFE MpG test scores have on GM / FoMoCo / Stellantis,
your next question will be how to stop them.

Generally speaking, though, operating temp of 212F is worth an MpG (just one) over an operating temp of 194F.

 

[COElkFreak]

Well took of for a two hour drive to take the kid to the airport. It’s better but not too impressed. Stayed around 178-188 except for waiting to drop him off. With no air flow that makes sense. But back on the road it cooled back off. I ordered a aftermarket cooler so I’ll add that next.