The Denali T case is a set 30/70 power split IIRC. Thinking that's what I was told on our '06. It's a 6.0/4L65e according to Comp Nine. 65 is supposed to be Corvette spec super duty 60.
Close enough. 62/38. So a little closer to 60/40. Anyway, and yes, they all came behind 4l65e’s. The biggest difference in the 60e vs 65e was that the 65’s had 5 pinion planetaries from the factory and 60’s only had 4 pinion. The 65’s also had hardened output shafts and sun gear, high energy clutch packs, an extra clutch in the 3-4 pack and a deeper pan. A few other small upgrades as well. So no doubt it was stronger than a 60 any day.
Actually when people say that they’re making or buying a, “built”, 4k60e what they really mean, or are hoping for, is a 4l65e.
But from all of my research, a factory 4l80e is stronger and MUCH cheaper than trying to build a 4l60e to handle high torque.
But they aren’t without their drawbacks though if you’re talking conversion. If it’s a 2WD conversion it’s relatively easy and cheap. You just need a flex plate and crank sleeve adapter, repin your factory plug, or buy a jumper harness, and find the proper length drive shaft out of something that came with a 4l80e from the factory in your same length vehicle. Since the overall length of the 80 is longer.
For a 4WD, you need a T case from a 4l80e or you have to tear yours apart and change out the input to the correct spline count. Then the correct drive shafts, or custom made if it’s not going into anything that ever came from the factory that way.
Anyway, it’s kind of like old hot rider guys knew that over a certain HP number, you wanted to go from a TH350 to a TH400. But that doesn’t mean that with enough $$ that you can’t replace everything inside of a TH350 to make it hold more power. It just isn’t very cost effective to do it.