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2022 Trans temp...

hdhp

By hdhp
in 6.6L Gas V8 (L8T)

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Pryme Senior Enthusiast

Pryme

Posted
Posted
On 8/21/2025 at 9:40 AM, Epsilon Plus said:

I've been considering putting an aftermarket stacked plate/fan cooler on the truck. In Arizona often 110+ ambient temps, my truck has been hitting 216°F idling in the school pickup line with no air moving. My 22 has the 158°F thermostat. However, bypassing it will not solve the high temp from stand still issue.

 

Instead of tapping the factory lines and introducing a leak risk I'm considering deleting the radiator/stock tube/fin cooler and doing braided -AN lines direct to the cooler and back like I had on my GTO.

 

I wonder what the BTU/Hr removal rate of the stock cooler is. If anything, going through the radiator especially at rest is acting more like a trans heater than a cooler. I should probably leave the trans thermo in though so the fluid doesn't run too cold when it's 45°f ambient out and not 110+. The aux cooler fan thermo would be 180°F on.

 

Little disappointed in the stock setup that it can't handle 15 mins of idling without going to towing heavy up a hill temps. Blame the clutch fan at idle I suppose.

My kids take the bus like I did as a kid. Can’t have them too spoiled lol. 

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newdude
newdude

Gas and diesel.  Gas got it 2020, Diesels got it 2017 with the L5P.  17-19 L5Ps, the thermostat is up near the radiator instead of by the trans.   Not sure what temp the L5P stat opens full,

mrjulian416
mrjulian416

Actually that's low. Normal non loaded temp is around 195

newdude
newdude

Normal for towing.  

Epsilon Plus Enthusiast

Epsilon Plus

Posted
Posted

The issue isn't the surface area of the stock cooler, its the lack of airflow. It could be the size of the whole radiator but no air = no thermal transfer.

 

A proper aux cooler with a fan like I posted would work great, but custom mounting is a challenge.

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Chuck FB Enthusiast

Chuck FB

Posted
Posted

I notice when I looked up the radiators fluid fan clutches for the duramax vs the L8T, the duramax has an electrical connection so I assume it has external means of engaging the fan vs the more traditional heat sensing clutch on the L8T. Of course me saying that they could have easily added a higher capacity cooling package to the L8T platform without much additional cost doesn't help you or me with what they did create. However this talk of cooling reminds me of retrofit double electric fan kits that were made to fit on various GM trucks of various years and the mechanical fan was eliminated, not sure how they worked in practice but the idea seemed good to run fans at low ground and engine speeds where the mechanical fan doesn't shine. 

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Tyler Gibbs Enthusiast

Tyler Gibbs

Posted
Posted
On 10/23/2025 at 1:46 PM, AndrewF said:

FYI- PPE does make a larger transmission cooler specifically for the 6.6 gas trucks now. Both 6L90 and 10L1000 :)  

 

https://ppepower.com/products/bar-and-plate-transmission-cooler-2020-2025-gm-2500-3500hd-6-6l-gas-6l90-10l1000

That thang looks pretty stinkin beefy.  The drop-in plug and play is amazing as well.  I think that's a winner.

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