Hi - I have a 1985 Sunrader which has 47 k on it (recently bought). Has auto trans. with od. I plan to put a transmission cooler on it and drain/refill it with Dexron 111. I assume it has Dexron 11 now. It works perfectly now but will be taken on a trip over the Cascades and Rockies soon and we want to be sure it runs cool enough (hardly ever use the od). Any thoughts appreciated.