I’m getting a noise coming from the wheels on my Subaru almost like the tyres are juddering when on full lock. Does anyone know if this is suppose to happen or it might have something to do with the central diff ??

Is it a regular rattling sound from the hubs on hard lock or are the wheels/tyres actually scrubbing?

If its just the rattly noise then possibly CV joints running a bit dry, worth spending a couple of hours repacking the joints with fresh CV joint grease, will cost you about a tenner for a tin of CV grease and the cost of new clips to resecure the rubber boots....if you're going to try repacking the joints do the inners as well as the outers.

I suggest this because you have nothing to lose other than some time and £20 tops, you'll gain an extra few years from your drive shafts even if it turns out not to be the cause.