Towing up Mountain Pass - 210F Engine and 199F Transmission

[B-train]

I'm in the process of buying a used 2021 Yukon Denali 6.2L. A key thing for us is towing a 5,300lb 7 x 14 cargo trailer converted to a camper. In Southern Oregon we can't go anywhere without going over 4300 - 5200ft mountain passes and our old car overheats at 70F ambient or hotter.

Did a test today.... of a used 2021 Yukon Denali pulling 5,300lb trailer at 107F in the valley and 101F at the top of I-5 and the vehicle drove right on up/over reaching 200F Engine and 199F Transmission at 60mph. Interestingly when we got back and putting the trailer away, the Engine gauge changed from 200 to 210 at top / center and was showing 210F - e.g. no air flow at 1Mph backing the trailer into it's storage spot?
View attachment 406078View attachment 406080

Can someone confirm that 200-210F Engine and 199F Transmission is reasonably normal for going up 10mile, 6% grades at 100F+ ambient? Seems OK to me. I read on this forum about Transmission coolers but seemed like not needed at only 200F as things can go up to 230F? before red-alert.


On another note, it's interesting that the hitch is 22-23" above the ground and this model (Denali Premium) does not have the height adjustment feature. The trailer ball top needs to be at 14.5" so a deep drop hitch is going to be needed.

I'd say that is pretty normal, and concur with the other input here. What I can say about the needle jumping up when you slowed down and parked it - this is due heat soaking of all the components, along with diminished airflow.

On road trips, especially ar higher speeds, or pulling long grades, I never shut my truck off for fuel or rest stops. Keeping airflow and fluid movement will prevent heat spikes.

I'd recommend just letting your truck idle for 5 or 10 minutes with the AC off when you do a pull like that to let everything settle out. Happy trails! I like your setup

 

[thill466]

Those numbers are fine, if not great. 100 degree's over outside ambient temp while towing is normal.

 

[Sparksalot]

I like Derale cooling products; several of my customers run them and have yet to hear anything negative. One guy has a 383 in a square body for whom I built a 700R4 a few years back. Told me that prior to the rebuild his trans temps would exceed 210 on a reg basis in the summer. After I built the trans he put a Derale cooler on and told me it keeps his temps at 175-180 max.

What are the line sizes for a 6L80, and is the included hardware adequate, or is the remote install kit desirable?

 

[NickTransmissions]

What are the line sizes for a 6L80, and is the included hardware adequate, or is the remote install kit desirable?

ADDING TRANS COOLER TO 2012 5.3 6L80

So I am buying a trailer and the transmission is only cooled by the lines going into the radiator. Without towing, the transmission gets up to 220 on a hot day. I swapped the fluid and filter and now adding a cooler. I got the tru cool 40x cooler low pressure drop, and the oil cooler manifold...

www.tahoeyukonforum.com

See post #3

Check and confirm w/Derale to determine needed hardware but most of those kits come w/everything to mount it.

 

[Sparksalot]

ADDING TRANS COOLER TO 2012 5.3 6L80

So I am buying a trailer and the transmission is only cooled by the lines going into the radiator. Without towing, the transmission gets up to 220 on a hot day. I swapped the fluid and filter and now adding a cooler. I got the tru cool 40x cooler low pressure drop, and the oil cooler manifold...

www.tahoeyukonforum.com

See post #3

Check and confirm w/Derale to determine needed hardware but most of those kits come w/everything to mount it.

Thanks!

 

[Geotrash]

Here is GM's word on temperatures with Dexron VI based transmissions (in the case mentioned below it was the 6L80):

In the February 2011 issue of Trailer Life magazine RV Clinic in response to a reader about the maximum transmission temperature allowed in a 2009 Chevy Silverado, the Tech Team had this response.

“General Motors’ in-house towing team expert provided RV Clinic with this statement: The maximum allowable automatic transmission fluid temperature is dictated by the transmission oil itself. The oil begins to degrade significantly above 270 degrees Fahrenheit, so we design vehicles so that in all but the most extreme conditions, the fluid temperature in the transmission sump stays below 270 degrees F.

We allow for up to 285 degrees F in extreme conditions (i.e. towing a trailer with combination loaded at GCWR in Death Valley). But for customer usage anywhere else in the country, even at GCWR, transmission sump temperature should stay well below 270 degrees F. Above this point, certain internal components, such as seals, begin to disintegrate rather quickly. Although newer synthetic fluids can withstand higher temperatures we still recommend this (270F) as a maximum temperature."

xxxxxxx

For my part, I tow a 7500 lb camper with a 2012 Yukon XL Denali with the 6.2. Pulling up a long 8%+ twisty grade over the blue ridge on a hot summer day, I might see transmission temps of 235ºF and coolant temps of 225ºF with my current setup, by the time I get to the top and cross under the Skyline Drive. This is higher than anything I experienced in the Rockies with the same setup in the summer of 2021. And I don't worry about this at all. I change my transmission fluid every 25K on my tow rig for added insurance.

I have a 2-row Cold Case radiator and a Derale 13960 fan-forced transmission cooler mounted below the front bumper, and plumbed in series with the radiator's transmission cooler that's built into the end tank on it. I estimate that the performance of this modified cooling system is only 5-10% better than the factory stock setup on the XL Denali (with the towing package), so if I had it to do over again, I would probably leave the cooling system all stock.

 

[PA-WOODCHUCK]

Only way to know true temperature id with look at scanner data. dash gauges can be misleading.

 

[avalonandl]

Thanks folks - will monitor for <=180F Transmission Temps on a sustained basis.

I have to say that I really like the vehicle, but... I miss a shift handle as part of the console! Had one in most vehicles all my life since my 1st - a 66 mustang 6-cyclinder 3-speed (rattled like crazy). The R/D pull to engage and the -L+ for individual gears takes the sport-fun out of it. Love the clutch less shifter feature in my 2004 Cad SRX V8 - a lot of fun.

Trans temps over 200 are fine. Dexron 6 is fine till 230+

The charts that show your burning your trans at over 180 are out of date... Thats from the 70's

 

[Marky Dissod]

The charts that show you are burning your trans at over 180F are out of date ... That's from the 70's

And in the '70s they didn't have Dexron6, which in fact supports your assertion that those charts are out of date.

That in and of itself does not make those charts bad advice.

Biggest reason why GM wants hotter motor oil and ATF temps is to satisfy CAFE MpG test scores.
Otherwise, they'll sell less replacement engines, transmissions, and/or vehicles.

If you are not towing or hauling heavy, ATF temps about ≈212F / 100C or less are not worth concern.
Whether or not you are towing or hauling heavy, every time ANY of them is indicated to have reached 230F, I'd change the motor oil, AND the ATF, AND the antifreeze.

Y'all need to remember, that motor oil / ATF / antifreeze temperatures are not measured at the hottest points in their respective systems.
If you see motor oil / ATF /antifreeze temps over 230F, be sure that, somewhere else, that fluid is even hotter than where that measurement is being taken.

 

[tagexpcom]

An update - winter towing 5300lb trailer transmission temps....

Just did a 700mile trip thru Southern OR - Northern CA with several mountain passes. Ambient was around 55F. The transmission temp has a base of ~152F driving flat down I-5 at 65mph. Going up a few 10mile, 5-6% grade, mountain passes the transmission ranged from 175-180 as the peak at the top of the climbs.