hard steering f-100

[flathead 53]

I have a 53 f-100 ,replaced steering box , tie rod ends ,center link ,rebuilt drag link,correct adjustment on steering box , truck steers hard when backing up or moving slow ,king pins are good ,only items not replaced are outer and inner wheel bearings , A good friend has a 52 f-1 pick up and it steers a lot easier then mine. I also have new tires ,same as his ,and run 36 lbs pressure in them ,I am lost on what the problem can be .