As a master automotive…
As a master automotive technician for 30 years I am GM trained, I own a 2015 and 2017 Silverados and knew back then that you should NOT get the 8 spd transmission. GM has had constant issues with camshafts and lifters in the 5.3 and 6.0 and 6.2 in all of these engines. I have been replacing camshafts or/and lifters since 2012. The new 2.7 engines are known for the squeaks coming from the idler pulley bearing. The 2.7 does not have a tensioner just an idler. The only reason I still have my truck's at 127,000 miles without going into the engine is because of the range technology device I have in the data link connector that keeps the engine control module from going into four cylinder mode.