Haven’t heard that but the 6.6 L8T gas engine arrived in 2020 with a 6 speed auto, the 6L90 or perhaps an upgraded version of it. The same year, the Duramax got the “ Allison Clone” 10 speed. Now, in 2025, the 6.6 L8T engine gets the “ Allison Clone “ 10 speed. If the story is that the 6L90 couldn’t handle the torque maybe that’s true.
My 6L90 in my 6.0 3/4 ton has over 265,000 miles on it with no issues except a slightly delayed shift into reverse. I plan to do a pan drop this weekend to see what the wear materials look like.
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