I've got my 87 turbo buick pretty much leak free except I keep finding transmission fluid accumulating at the bottom of the radiator drain petcock on the passenger side. It's a small leak and doesn't drip on the floor, but it is red and dripping from the petcock. It has an auxiliary transmission cooler. All the lines look good and dry. I'm not sure where else to look to chase this down and try to fix. Anyone have any ideas?