I have an H55 and 3.70 gears, and have run 235/85's, and it works very well. I'm at a little over 2k rpm at 60mph, and 2500 at 75mph. The 2F doesn't have the grunt that a 12ht does, so if my gasser can do it I'm sure your diesel can too. I've not done much towing with it, but towing with...