The overcenter adjustement is on top of the steering box on the very front of the box. If you are standing in front of the truck, facing the truck, look down, almost straight down the right edge of the fan cowling. You'll see the steering gear box. On top is a 5/8 nut tightened over an Allen Head bolt. I don't remember the Allen Head size. While holding the Allen Head bolt stationary (so you know where you started), loosen the lock nut with the 5/8 wrench. Move the bolt clockwise to tighten and CCW to loosen the overcenter. Mine was a CCW move to ease the tightness). The book recommends 1/8 at a time. I agree. A little can go a long way. You may want to put a mark indicating where you started in case you have a problem. The lock nut needs to be snugged good to prevent leaking.