if i get what you are asking.....your traction is going to be dependent on your tires grip with the road (snow, slush, ice etc)..the point where you lose the grip is what you need to find. you cannot really plan or do much about black ice, or ice under snow you cannot see. typically each storm has its own "grippyness". some snow is sticky and gives good traction where other storms are mealy and does not offer much traction. i will start by feeling out corners. most times you cannot push the corners like when the road is bare (same speed). so if i can typically take the corner at 50 ill try 40 to 45 and see how it feels. do the tires slide/push in the corner? if so slow down a bit. i can usually get up to normal speeds on straight aways and up hills.
i have used both 4auto and 4lock. i have not noticed a difference at speed. the transition was always very seamless. from a stop i almost always want to be in 4lock. there are many variables you cannot account for (bumps, humps, twists etc) that can throw off the trucks momentum and cause it to act different (slide, spin, kick out etc). the biggest thing is to not push it too far and stay steady. yry not to break too much or at once going down hill and try to anticipate as much as possible. see things happening before they do. i drive on back roads (no highway) and up over a mountain everyday. we work no matter what. around here if school is cancelled, the plows tend to sleep in. tires are the biggest improvement. true snow tires