Actually the most bullet proof I have seen is the 2-3 people that have put in a 4T80
And that just makes sense, since GM uses the 80 without the "T" in a variety of heavy duty applications. I have always wondered about a Former Admins statements that the "80" is harder to push and takes away HP. Never added up to me.
compare the internals of an 80 versus a 60 or 65.... quite a difference in size and weight of LOTS of parts, especially gears. it most certainly does sap more power, but i believe the tradeoff would be worth it if you question the 60E or 65Es ability to survive.
The 80 weighs some 80ish lbs heavier than the 60 overall. Surely it does take power, but in the power to ground reality test... if there'* a "snap" somewhere between flexplate and tires, that'* not good.
John.. Funny side mention about the 80 being in many RWD applications. The trans in my truck is a 60. That was a big surprise when I noticed it. That trans has been through hell and still lives to talk about it.