Nissan Patrol 4x4 (Africa)

My 2000 4.5 patrol have a slight vibration on the steering at about 100kph. This is more noticable when going over uneven patches,feels like the front wheels are floating a bit. When the camping trailer is hitched this vibration becomes much worse, again at 100. When braking in a straight line everything is fine, but braking in a curve the vibration becomes very bad. There is not much vibration when braking with no trailer, only when the trailer is hitched. Since the problem I have rotated the wheels, had alignment and balancing done, new shocks, new steering damper, disks done and new ball joints on the steering arm and drag link,two different guys also checked the front bearings and found no problems. Anyone with any ideas of what to do next?

Front panhard rod bushes?

Had them checked, they are fine. Will do the alignment again to see if it makes a difference.

Are the kingpin bearings pre-loaded correctly, and where the wheels balanced on a central cone or on their bolt holes?