Yup, mine's an auto, bought because it was recommended for towing up to 3T. As it is, we never bought the 5th wheeler that we'd intended to get, and so we're only hauling 1.8T around - but I'd still prefer to do it in an auto.
Ray, the factory clutch is not the strongest beast around and if your dealer was half as smart as they should have been, they'd have told you to get the auto if you were towing that much weight.
There's no way the transfer case can change from LO to HI range and the D40 will be driving all 4 wheels in both HI and LO, so the slightest turn of the wheel and you're not just using up clutch, you're stretching transfer chain as well. If you had the D22, you could leave the front hubs unlocked.
I suppose if you don't do any 4WDing you could have the front propeller shaft removed which at least gets rid of that problem, but you'd have to climb the hill completely in 4LO because there's no way to switch out until you've stopped the vehicle, put the gearbox in neutral, pressed the brake, place 3 freshly picked white onions on the dash and sung 'Silent Night' in Swahili with an Irish accent.