Strange noise advice please

Could be a number of things. Your gona have to get dirty and check the condition of the props. The condition of the diff for backlash and input bearing. Might be worth having some one move about the vehicle whilst it is producing the noise and try to establish the rough area it's comming from.

Very likely a propshaft UJ - rear of the front is the most lilkey suspect. Chock the rear wheels and jack up one front wheel with the trasfer box in neutral so there is no load on the propshaft. If that's not it, do rear in the same manner.

Richard