I think when you have a heavy rig 30ft or more, loaded or unloaded It is my humble opinion you are in tow haul territory. That being said, I have used it both ways. Love it going up big long grades and down works great. It doesn't search as much or at all for the right hear. That's what I'm looking for. Another plus is tranny temp that stays down. Talked to a Ford mechanic when having service asked about it. 25 years experience his like for the TH was up/down grades. He also added that with my rig, no slide, I had more ccc, but regardless he said I was already towing, why not use it. In addition the TH mated to the 5sd torqshift was in tented in this manner. On the flats dealers choice. Just my 2c's.