I got a k2500 6.5 with a 4l80e Trans, we want to use this to tow one of our hourse trailers, that weighs about 11-12k fully loaded with it. Is this to much for the truck? Also it has a shift patern is D,3,2,1 should I use 3rd to tow in and use 1st and 2nd to take off from a dead stop or put it into drive and at about 30mph or so shift into 3rd to prevent from towing in OD?