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On average, I'm seeing 5-20°F degree temp drops compared to previous towing temps.
It's hard to nail down exactly as there's so many variables like weather, route, and grade. I don't have a good sense of non-laden temps as I'm only usually monitoring when towing. This particular trip was in early summer with temps in the 90s.
Towing on the level, pan and torque converter temps hover in the 190s. Not that much lower and maybe about 5 degrees lower at cruise versus prior.
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Torque converter temps are pretty dynamic, but there is definitely a bigger difference in pan temps staying lower and be able to sink heat in passing and grades with less or slower rise. Faster fall. Previously, when downshifting to 2nd in steep grades for engine braking, I could reliably see torque converter temps spike right to 230°F. Now I'm seeing that in the 210°F.
One of the main reasons for more trans cooling was for brutal long grades where I could reliability trip the torque converter lockup logic at 266°F torque converter temp and 203°F engine coolant. Once tripped, the transmission will aggressively lockup 4th, 3rd, and even 2nd gear. This greatly reduces heat produced in the torque converter at which point it tracks close to pan temps. Problem is the pan temps will continue to climb and I can get it over 250°F at which point I let up hovering around 4k engine RPM, giving into some mechanical sympathy. I've never tripped the 302°F threshold and credit to the robust OEM cooling as moving 15k+ lbs on 35s is some work.
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With the additional cooler, I can still trip the lockup logic if I'm super aggressive with basically the gas to the floor and engine screaming near redline for 5-10 minutes at a time. Notice the computed HP and TQ at 413hp and 390 lb-ft (OBD a bit optimistic)...it's basically engine output that drives heat in the transmission and I'm flogging it at max output. I was sure I could trip the lockup logic as I've been able to do that even when it's 40°F in winter. So I was pretty sure no amount of extra aux tranny cooling can prevent that.
Where it earns its keep is that pan temps do seem moderated staying pulled down more. It doesn't feel like it will continue to march into higher temps even when caning it for extended periods. I did just touch 240°F and ran out of hill (Grapevine CA). Still would like to test it in the Sierra's in later summer, but it already feels more resilient.
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