2012 Buick Enclave - Slips and studders

slipping and shuttering around 1600-1800 RPM

are you sure the tranny is slipping? if it is you should visit a good tranny shop. chevy has had this problem with newer vehicles and it was fixed with a fluid and filter change. but it could be the engine missing at those RPMs and feel like a shutter.

I have a 2020 Envision 2.4. I have a very slight shutter at the same rpms. I initially thought it was torque converter shutter, but when I turn off the A.C. I have yet had it to happen. So right now I’m considering it normal shudder cause by the A.C. compressor.
@weekend-warrior could you direct me to the info source to the transmission problem you stated?

here are a few examples…
8-Speed GM Transmission Problems Fixed Via New TSB | GM Authority

GM To Replace Transmissions In Some 2021 Chevy Silverado, GMC Sierra Units (gmauthority.com)
[TSB Seems To Fix 8-Speed Automatic GM Transmission Problems | Stingray Corvette Forum (stingrayforums.com)]
(TSB Seems To Fix 8-Speed Automatic GM Transmission Problems | Stingray Corvette Forum)

2016 Camaro Transmission Fluid Change (SHUDDER PROBLEM FIXED!) - YouTube