I went through this on my 65. Turns out when I was under there and buddy was turning wheel, the: steering box was loose, tie rods were soft, Idler arm was shot, and LBJ's wer bad. All this on a car that hadnt been driven for 25 years. Idler arm was biggest culprit as it was just deflecting up and down. Coupler was OK, tightened up steering box, changed bad joints and adjusted steering box. Loosen lock nut on top of box about 1/4 turn. Turn slotted screw CW while turning wheel back and forth over "high spot"at center travel. Youll feel wheel getting tighter. You dont want it too tight, once its where you like it, tighten lock nut.
