This spring we purchased a 3600RL, dry weight 12,000, and am pulling with an '08 Dodge, Quad Cab, single wheel, short box 4X4. This truck has a 6.7 Cummins with a builtin Jake Brake, Tow/Haul and Auto 6 tranny. So far about 10,000Km and the unit is fabulous. Mileage while pulling in Canadian...