Hello. I'm so "over the moon" (in a good way) about my new 2015 Chevrolet Silverado LT 4x4 truck. After the last 2 winters in Tennessee, I neede a full size 4x4 pickup so that I can have "peace of mind" in case of the next winter like the last 2. This is the 2nd Chevrolet that I've owned outright. The 1st was a mid 90s S-10 pickup. My Silverado has an AUTOTRAC transfer case. Need suggestions on when to use it during heavy rain. Thank you.