@j91z28d1
Amsoil ATL would be good. I've used it a lot over the yrs. Good stuff. I have 30+ qts on the shelf here. I bought it for a great price from an Amsoil dealer that was moving out of state and didn't want to haul it. I have plenty of Dexron6 too.
I started (Oct of 2018) with a VERY used 130K mile 07 Yukon Denali that we bought off a used car lot with who know what for mx history.
I immediately concluded it needed an engine rear main seal. So out comes the transfer case, tranny and torque converter to get to the rear main seal.
While The tranny was out I changed its fluid, filter, torque converter. and a couple of other seals & o-rings while I was in there. All new ACDelco Dexron6 went back in, 11-12 qts.
2+ yrs and 26k miles later I did a used atf analysis. I left the fluid and filter in place. Then 2+ more yrs and 17k more miles (43k miles total on fluid and filter) I did another analysis. I decided to change both fluid and filter, 6 qts). ACDelco Dexron6 went back in. My tranny mx schedule now is to change whatever I can get out of the pan (5-6 qts) every 25k miles, then at 50k change the filter too.
Here a thread I did in 2018 with a lot of pics of taking tranny out, xfer case, changing atf, etc etc:
https://www.tahoeyukonforum.com/threads/rear-main-seal-job-pan-etc-07-yukon-denali-6-2.108334/page-3