In my searching of the intrawebs last night i found alot actually talking about this notorious th400 whining. Appearently the 400's are known for it. I had found the biggest three things for the cause was 1. Clogged filter, straining the pump 2. Low fluid level 3. Extra cooler line, or bigger tranny cooler. Requiring more pressure to push the fluid threw your cooler.
Im going to change out my filter, and then recheck fluid. But i did add a massive electric tranny fan with lines that run the full length of my blazer. It is seeming i may need an upgraded pump to push more fluid through my system.
I will take a look at my free play on the tc tho although i know i checked it on the install amd determined it was good. Doesnt hurt to double check.