1967 dart 270 /6 225 auto

put in a new radiator a few months back. didnt drive it that much. started driving it more recently, and within the past week the tranny has developed an awful winding/whine to it. it goes with the rpms of the engine, just like a power steering pump would, but only when OUT of park.
park it for a bit and its ok for the first minute or so of driving, then it sounds like rushing liquid, or more rather like liquid hitting fan blades and definate swishing running liquid, then the whine. checked the fluid, it's ok. other than that, im transmission dumb. the noise hits its absolute worst when the brake pedal is holding the car firm, and then stepping on the gas while in reverse. really brings out the cat being stepped on noise.

im parkin it !!! any clues?

Is it possible the transmission cooler is clogged and causing it to overheat? Is the fluid frothy?

no the fluid isnt frothy. i was thinking the same thing about the cooling lines. i sucked a LOT of solder out of the new radiator with a shop vac when i got it.

If you didn't get it all and some ended up in the tranny... well... that could be ugly. There shouldn't be any loose solder left inside a properly manufactured radiator...