F-350 single rear tire, 6.0, auto, 4x4 pulling a gooseneck with john deere 4460, scales 26800lbs. pulled fine, noticeably heavy of course, but when I went thru a slight incline clover leaf ramp turn to the left, the steering wheel tried to "center" itself, was jerking to pull it back straight. with the weight on the rear in slight turn, I suspect the front axle U-joints, I have them and new ball joints and idler bushing as well, since I will be in there anyway. the tie rod ends and rest of linkage is good, typical.never have had problems in the past, not a daily driver, just my work horse farm truck. any other ideas?