I know that this is a zf5 thread, but FWIW, Towing my 10K trailer with Raylan - e4od & 4.10 gears it's happiest cruising at about 2500 and above. Much below 2500 egts, coolent and to a lesser extent tranny temps climb. Also, if I let it drop below 2500, when I put my foot in it for a hill, I...