Today we got a pretty good snow storm going where I live, and the g/f wanted a pop form the store half a block away. I got a 99 Silverado 5.7 4x4. So I jump in the truck for a quick run to the store. I pull out of the drive way, some tire spin on the snow and ice, completely intentional. Pull into the store grab pop, and back in truck. I pull back onto the road and hear this awful grinding when I break traction. Immediately off the gas, and it goes away. Give her the gas again, same awful grind. Pull into the back yard to see If i can figure it out. Any time it breaks traction that grinding comes back, but sitting at a idle or rolling it is fine. 2 wheel, 4 wheel, only grinding when I break traction. Toss it in reverse to back out of the yard, and grinding starts again w/o even taking my foot off the brake. If I let of brake and give it gas there is no power, will not reverse, the whole time it makes the grinding noise so I don't give it a lot of effort before I abandon that and push it back onto driveway. Any ideas? I checked my local Craigslist and found a 4l60e out of a 99 jimmy 4x4, if it is major tranny problem, will that transmission swap in? I am a bit of a "back yard" mechanic, anytime something breaks I fix it myself, but its awfully cold and snowing out and the garage is to full to pull the truck in at the moment. Not crawling under it or cleaning out the bay till at least tomorrow, when it lets up. Any advise or insight is greatly appreciated.