I recently had a ECU Remap to increase power and torque. With the extra power it definitely holds 4th gear going up a raise towing a camper trailer weighing about 800kgs + a truck full of humans and gear. I do run a 285 tyre and 4.56 diff ratios. With the tyres and ratios I hated the way the truck towed, but after going with the ECU remap it is a different truck all together now.