In most cases there is a coolant heat exchange that actually warms the transmission fluid in the cold weather. so the trans should stay warm enough When i went to the DD pan i didnt notice it running any cooler on the guage just cruising down the highway in lockup. ,if it was it was maybe 5-10 degrees if that. But once in stop and go traffic and trailer pulling the trans temps were much more stable it lowered the peak temp by quite a bit,i used to get 180 in the pan on oocasion,with the DD pan it rarley goes over 160 now,so overall the temps will be more consistent,and fluctuate less,and from what ive seen at least a 20 degree drop in your highest temp.