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

[tagexpcom]

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?


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.

 

[NickTransmissions]

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.

Keep trans temps at 180 degrees max on a sustained basis. A couple momentary exposures to 200F are fine however if it keeps happening, change the fluid, install a huge aftermarket trans cooler, deep pan and do what you need to do to allow for continuous trans fluid flow through the system vs getting stuck behind some cooler bypass valve, if it is applicable to your vehicle.

At 230 degrees, fluid begins to break down and internal trans damage can ensue so unless you have a warranty, either you're (or someone on your behalf is) pulling it out, throwing it on the bench and tearing it down in prep for overhaul.

Im not familiar with the 8 and 10 speed units so if you have one of those i can only speak to them in general terms.

 

[Sparksalot]

Keep trans temps at 180 degrees max on a sustained basis. A couple momentary exposures to 200F are fine however if it keeps happening, change the fluid, install a huge aftermarket trans cooler, deep pan and do what you need to do to allow for continuous trans fluid flow through the system vs getting stuck behind some cooler bypass valve, if it is applicable to your vehicle.

At 230 degrees, fluid begins to break down and internal trans damage can ensue so unless you have a warranty, either you're (or someone on your behalf is) pulling it out, throwing it on the bench and tearing it down in prep for overhaul.

Im not familiar with the 8 and 10 speed units so if you have one of those i can only speak to them in general terms.

What external cooler do you prefer?

 

[NickTransmissions]

What external cooler do you prefer?

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.

 

[Larryjb]

210 to 212 for engine temps is nothing. That's not even the boiling point of water, and is probably in the normal operating range. My '02 was going above that towing up the Coquihalla. I had to turn the heat on, AC off, and open the windows to keep temps under control.

Conversely, our 08 Explorer which has the 6 speed transmission (I believe it's the same 6 speed used in GM, but I could be wrong), I never had any concerns with engine temperature. Tranny temps tended to the 200F on long climbs, but came back down after. I should have changed the fluid after the trip but just haven't had the time (too many other urgent emergencies always come up!). But four years later there have been no transmission issues.

 

[NickTransmissions]

(I believe it's the same 6 speed used in GM, but I could be wrong)

Largely correct. The GM 6Ls and Ford 6Rs are both based on the ZF6HP26 produced by both GM and Ford under license from ZF. GM made fairly significant changes relative to the ZF6, especially with the pump assembly. Ford's 6R60/80/140 are much more faithful. Same applies to the GM and Ford 8 and 10-speeds in that they're based on their ZF counterparts.

In fact its common for Euro folks to swap Ford 6R80 pumps and input drums/shafts into heavily modded zf6hp26 units for their upgraded BMWs and Audis for the higher torque handling capacity of those parts relative to the ZF stuff as they were built to handle the higher torque put out by Ford Coyote and other engines.

There's your GM/Ford transmission trivia for the week, lol

 

[Doubeleive]

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.

your probably fine driving like a normal person, I drive it at 100+mph and things get a little warmer sometimes, hasn't been a problem
fun drive, I drove it about 115mph almost the whole way thru once north and south. little rental car held up to my torture lol

 

[tagexpcom]

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.

 

[swathdiver]

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.

The transmission and fluid is designed to operate into the 260s before the warnings happen. So you're good. If you do that kind of towing a lot, change the fluid half of what the severe service schedule is, about 18-20K miles. If my fluid ever got into the 230s or more, I would change it after the trip.

As for the drop hitch, take into account the sag a 14.5" couple height seems low. Most utility trailers I've used are 16 or 18 inches and we use a 5.5" or 6" drop hitch.

 

[tagexpcom]

Interesting. Here's a pic of the trailer - and level is ~14.5" to top of the ball. The Caddy's receiver is ~14" to the center.

I ordered Blue Ox BLU28XR Adjustable Drop Hitch Receiver Adapter - 2" Hitches - 8" Rise/Drop - 10,000 lbs - https://www.etrailer.com/tv-review-blue-ox-adjustable-hi-low-adapter-blu28xr.aspx



The 2004 SRX (pic above) has 320hp V8 and with Blue Ox stabilizer + weight distribution pulls OK - but overheats going up a even a moderate grade >60F. Have to have heater blaring to pull temp back down and haven't risked anything over 75F ambient

I have to say, the Yukon was waaaaaaaay better in yesterday's test - and at 107F - what a pleasure to drive!!