For $2 a quart savings - Valvoline Multi-vehicle fluid (13.99) vs GM's Auto-Trak II transfer case fluid (15.99), I'll take GM's OEM TC Auto-Trak II fluid every time. That is just me since it is only 2 quarts to change out (whopping $4 savings going the "recommened for" Valvoline route). You do you.
2018 Chevrolet Silverado - grease once a year. RED TACKY GREASE (or any grease meeting NLGI #2, Category LB or GC-LB) for the nine (9) zerks. use straight fitting and 90 degree with 36" hose lever grease gun.
(2) outer tie rod ends
(2) upper ball joints
(2) lower ball joints
(1) top of pitman...
2018 Chevrolet Silverado 2500HD 6.0L 4wd. 6qts WALMART SUPER TECH Advanced Synthetic (20,000 mi. rated or 1 year) 5w30 and a NAPA GOLD FIL 7060MP oil filter (50% off annual sale is when I stock up). Change Every 5,000 (OLM @ 20%) - 7,000 (OLM @ ~5%) miles.
Sometimes buy NAPA Full Synthetic...