Heater core would be the likely culprit here.
Find where the fluid is coming out and repair/replace it.
easiest way is to fill radiator and look and see where fluid is coming out, but Im sure you thought of that. The best way is to plug the ends of the radiator up with some type of rubber stopper then insert blow air through the drainport while holding it under water. Wherever the bubbles are coming from is where its leaking.
tranny cooler lines or tranny cooler blew up inside rad
"transmission fluid leaking from fitting below radiator cap after replacing radiator on 99 surburban
Probably your radiator fluid leaking out.
Antifreeze is green in color and is leaking from your radiator .
It is probably Radiator fluid that's leaking. if you have red radiator fluid. it looks purple when it heats up. I had this from my Toyota Sequoia when the leak went over the hot engine.
if you have an automatic transmission there should be cooling lines going to the radiator to cool the transmission fluid the lines could be leaking or the tank could be leaking
put radiator sealer in it or crack an egg in it
there is a transmission cooler inside your radiator and it must be leaking. probably replace the whole assembly
The transmission oil cooler inside the radiator is no good and allowing the fluids to mix. Not a good situation, don't drive it until it is fixed.
Because there are lines running from the radiator to the tranny, this lets the fluid flow through and be cooled so that it does not over heat in the tranny and cause damage to your bands inside your tranny.