You will need to eliminate the trans cooler circuit in the radiator as a possible culprit for your sludge. The oil cooler may have developed a pinhole leak. Check the trans fluid level as well. This will be certain death for the tranny if coolant gets in there. Have the trans cooler pressure tested to see if it holds pressure. If not, that may be your problem.
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.