LM2 and LZ0 DO NOT have a thermostat in the valve body.
LM2 and LZ0 still have the water to oil heat exchanger that the ATF goes through no matter what. So if the thermal bypass in the lines to the aux cooler is closed, ATF goes out the transmission, into the water to oil exchanger, to the thermostat and then back to the transmission.
When it gets hot enough to open the TBV in the line, it will then flow to the aux cooler out front to regulate temperatures.
The cooling system is going to warm the ATF up as the exchanger is part of that entire Active Thermal Management cooling system.
LM2 and LZ0 DO NOT have a thermostat in the valve body. Just the one in the lines. Stock TBV opens at 194F.
From TSB 22-NA-182
10 Speed (10L80, 10L90, 10L1000) - 143F (61C) - TBV is within the valve body on all listed applications except those equipped with 3.0 (LM2) (LZ0) Diesel. The (LM2) and (LZ0) Diesel, the TBV is on the frame rail, external to the transmission and opens at 194F (90C).
As for your big Duramax, the transmission cooler lines still flow through the side tank on the radiator, so deleting the TBV in the valve body will only lower it so much.
Installed the PPE bypass on the RST last week. With ambient temps between 75-95, the trans temp dropped from 195-198 unloaded to between 180-185. Not what I was expecting (also has the Max Trailering package). I have a Nextgen diesel valve body upgrade kit going in this week and the remaining thermostat in the pressure regulator valve will be removed and I'll see what happens.
I did the same mod in the Valve body upgrade kit for my '24 3500 HD Duramax and I haven't seen much difference in trans temp but I've just been running back and forth to town so far.
It's going to last a long time. You seem to take care of your vehicles and that is key. I wish I kept my 2002 Silverado. These new vehicles are not built with quality anymore.
2022 Refresh LTZ with the console - I put a 4D tech Start/stop eliminator in the truck a week ago and it works great. Yes there are a number of panels you need to take off to get access but its not that hard to do. Figure I spent about 1-1/2 hrs doing the truck and another 10 minutes installing one in the wifes car - that had easy access.
Did they do this TSB from the post above?
New updated program required to get this running is #PIT6504 dated Apr 1 , 2026.
Appears the applications cover numerous Chevy and GMC vehicles with fwd col, AEB, and LKA options.
Hopefully this helps someone out in the future with these issues.
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