Trans temp confusion

[jfoj]

@StephenPT

Thanks for the info, 10 speed gear ratios should be the same regardless of engine. TCM tuning would be different. I would have assumed that the Diesel may have had a different rear axle ratio to take more advantage of the low RPM torque.

My 6.2l Yukon XL tends to operate at close to your RPM on fairly level road surface. My Yukon in in 10th gear typically by 55 MPH and will stay in 10th gear under a fair amount of loading. I have watched the trans stay in 10th gear up to about 95% loading before dropping to 9th gear, but this is only about 100 RPM different than 10th gear.

Interesting it seems the 6.2l and I assume maybe even the 5.3l operate at close to the same RPM at 70 MPH as the Diesel! Wonder if anyone has tried any taller tires on a Diesel to see what happens to the fuel economy and drivability.

Here is a general chart of RPM vs Speed on fairly flat highway. You can see after 70 MPH wind resistance starts to play a bigger factor in the loading.

55 MPH - 1200 RPM
60 MPH - 1300 RPM
65 MPH - 1400 RPM
70 MPH - 1500 RPM
75 MPH - 1620 RPM
80 MPH - 1720 RPM
85 MPH - 1840 RPM

 

[viven44]

For what it's worth - due to similarities to the GM 10 speed, wanted to provide the datapoint that on my new Ford with the 10-speed and 7.3 gas, the transmission temp wants to be at ~210 - 220F. No change with/without towing.

 

[jfoj]

Recently installed the NextGen valve body updates on by truck along with a PPE 2 1/2 quart larger aluminum finned pan. I bypassed the internal valve body cooling loop thermostat.

Drove 2 1/2 hours one way this past weekend in 105F ambient temps with 2 adults and light gear and trans temp temp did not go above 165F.

Had a few small spikes when passing or pulling grades were TCC unlocked or slipped more and trans downshifted, but temps dropped back to normal quickly once trans was back in 10th and TCC was locked back up.

Seems that running 80 MPH pushed the temp slightly higher to the 165F range, if I slowed down to 65-70 MPH temp dropped a few degrees.

I have a heat shield to install on the cross over pipe that runs just below the trans pan that may help with the temps slightly. Pretty simple hose clamp install for the shield.

$35 for the 1 foot by 4 inch shield. May not make much of a difference but figured the radiant heat from the exhaust running under the pan might elevate the temps slightly, especially when towing and the engine is loaded up.

Amazon.com

 

[tagexpcom]

We have a 2021 Yukon w/6.2L + 10speed but does not have 'tow package'. Added a brake controller and tow a 5500 cargo trailer (square box) in mountainous areas. We did a test at 107F ambient / hot afternoon up a 10mile, 6% grade I-5 interstate near our home at 60mph and the trans maxed out at 200F. We routinely top out at 180F'ish (175-190F) in milder 80-90F ambient on long mountain ups.

For regular driving - it's shows 150'ish I think.

 

[viven44]

Our 2024 Suburban towing ~7000 lbs for over 3-4 hours... ambient low 90s... the highest I ever saw it go was 169F.

The Ford 10 speed employs a plastic oil pan (good job Ford saving $$, lol) not sure if that is why but there is a lot of shielding around the pan and over the exhaust pipe.

 

[jfoj]

At least on your Ford, you can drop the trans pan with the exhaust in place. I would be swapping the plastic pan out with a PPE or some other aluminum pan by 20k miles just because. Something in the road could easily bounce up and crack that pan and the heat will get to it at some point as well.

At least for the 5.3l and 6.2l 1/2 ton 4WD GM trucks and SUV's the drivers side exhaust crosses over under the rear edge of the trans pan and this pipe is POST Catalytic Converter so it likely is VERY hot while cruising. GM stuck the converters up very close to the exhaust manifolds, it will be interesting to see how the under hood plastics and rubber is in 10 years after driving. The BMW's with the converters hanging on the exhaust on the rolled over straight 6 cylinder had so much under hood heat the plastics and rubber were compromised by year 8 and by year 10 they were really having problems.

Picture of PPE pan installed on my 2024 Yukon Denali, you can see the exhaust cross over at the bottom end of the picture, it is not a great shot, but it gives you an idea how close the pipe is, the pipe is even flattened out to save space. Maybe 1 1/2" clearance between the top of the exhaust and the trans pan. The heat shield may not do wonders, but it can't hurt IMHO. We shall see if I detect an improvement. I will not have enough data to tell if the change is subtle.

 

[viven44]

Yes it does look like the pan can be dropped with relative ease on the Ford. I recall having trouble on our 2018 Tahoe with the 6 speed. The driver side pipe fought me. I had to pry it away with ratchet strap and 2x4 on the subframe and managed to pull the pan out. On our 2024 it’s the same flat pipe deal as yours. That pipe is too flat for my liking. At some point I want to run my IR temp gauge on it. I expect it to be a restriction and should see a sharp temp difference before and after.

Yes, I’d like to swap the pan to metal at some point.

 

[jfoj]

Added the heat shield mentioned in my post above, seems to fit fine, but very close proximity overall. Hopefully it will help with radiant heat transferring to the trans pan from the Post Cat drivers side cross over pipe.