I have a 99 z28 and looks like transmission fluid is leaking at the radiator on the bottom. I tried tightening it up some at the nut and it moved a little. Worried why it is turning.

 

the lines to the rad are flared.....to much tq and they be stripped !

 

I just moved it a tad bit. Guess I will have to take it to the shop to fix it.

 

Three potentials:1) the thread on the flare fitting is stripped 2) flare of tubing is cracked 3) thread in radiator that accepts the flare tube nut is stripped.
Best solution to all three is to not use the radiator portion and add an aftermarket tranny fluid cooler. The tranny fluid cooler portion is low pressure as it's the return to sump/pan. An aftermarket cooler would also eliminate the possibility of tranny fluid leaking into the engine coolant portion of the radiator.