Shortly after buying my '03, okay the same day, I went throught the owner's manual page by page. I wasn't happy with the sections on towing while in OD so I wrote a letter to the Minneapolis office. I got a telephone call about two weeks later. The guy told me to leave it in OD unless it was hunting and pecking. So that's what I've done. My 48RE has worked great towing. It's empty that this transmission gives me the creeps. Anyhow, I am not up near you guys and your weight. My heaviest is 9000 lbs TT. Just my . 02.