Allison. GM guys play fast an loose with their drivetrain designations all the time.

Chevy should have never retired the 6L90. That transmission is a beast behind gas-motored HD trucks. Though I'm not going to lie, there is a gap between 2nd gear and 3rd gear where a 10-speed (if they were reliable) would be much appreciated. BYUFBDAD alluded to noticing such conditions above.

There are times while towing on my old 6.0, that if I miss my speed on a hill, I'm down to 2nd gear and 25mph and there is nothing I can do about it as I don't have the horsepower to overcome the steep gearing change between 2nd and 3rd.

Other than that, no complains from the 6L90 coupled to the 6.0 cast iron Vortec. That drivetrain is a beast and will keep going for hundreds of thousands of miles under hard conditions.