if you hit the loadhaul button on a 2004 dodge 2500 CTD will it let u in overdrive or just 3rd gear? Im going to be towing a 4000lb trailer. should i not even worry? I have a tranny cooler on. Must be factory? Are all dodge tranny cooolers external now?(not in rad anymore)

Just push the button and let er RIP!!! If its not changing to much leave it in OD.