I’ve used the valvoline ULV in my 10r80 and it is good. I tried amsoils recommended fluid, an LV, and even only with 6 quarts swapped it was not a good match. Shifting was clunky, variable TC engagement was lost and it generally made it clumsy.
my 10r80 had ALL of the horror story complaints happening. Consistently bad shifts out of 3rd, and increasing occurrences of it giving up and going to neutral after notching the shifts in traffic and getting confused. I did several fluid changes after the dealer was no help, and found that a tiny splash (about 2oz) of lubeguard red was a radical, total, and life-altering fix, after getting the amsoil out and the ULV back in. It shifts as well if not better than our Lexus GS, which is a highly refined, quick, and well-sorted 8-speed. I would NOT use a full treatment of LG, but if I was doing a trans service would highly advise of adding just an ounce or two in.