I agree with your decision. I have a 2014 Sierra CC SLE with 112K on it. Alot of small quirks I have corrected and the AC condenser once under warranty, but the engine and transmission has been good. I have done a few drain and refills and installed a sure cool thermostat bypass but I too am scared of the torque converter as well as the lifter issues. But I figure even at 3-6K for a trans replacement or engine top end rebuild I am light years ahead of the price of a new truck with no guarantee it will not have issues from the get-go. Of Course, mine being in real nice condition plays into my decision too. A gut at work let me drive a brand-new Tundra the other day and it was impressive and sounded cool when I stomped on the gas a bit, but the dash is still hard plastic, and the seating is not as comfortable as my Sierra. I am not knocking it but I did not see 45-60K difference in it and mine so I am rolling the dice mine will keep rolling. And that goes for new models from the big three as well.