AW4 Tran starts in second.............

I was just out in the backyard and was trying to build me a little set of ruts to play in and then my transmission would only start in second gear. I let it cool down and the fluid level was fine and then it went back to normal. Is this normal? I have a extra tranny cooler because it did this once before. Was I just too hard on it or is something failing? I have one more question, on the stock radiator trans cooling lines, which line flows into the radiator frome the trans and which is the one from the radiator to the trans? I want to make sure that the extra cooler is connected to the right line........