I have a 2012 silverado with the 5.3 engine and 6 speed trans 4x4 and noticed when trans is cold it does a slip shift from 2to 3 rd engine rpm flares up aprox 300 to 400rpm ,if realy cold out it maybe will do it again ,normaly it does this once and only noticed this problem? from 2 to 3rd shift, oh forgot to mention the truck has 400 kilometers on it and did it from new didn't even use first tank of gas .is this normal? is there a software update?