Dave, the clonk comes from moving the steering wheel slightly with the wheels on the ground. Look closely at the centre of the rack when the steering wheel is rocked very slightly, and you will see the rack moving very slightly vertically under the load. Repeat that with the wheels off the ground and there will be no clonk.
Mine is the same.
Doesn’t that perhaps suggest wear thus insufficient meshing between the rack teeth and those of the pinion perhaps? Cannot remember without going out to the garage to look at my rack but usually on racks in general there is a shimmed adjustment which bears on a pad that in turn bears on the smooth side of the rack to preload the engagement between it and the pinion.
