Chevrolet Silverado (2004) 2WD 1500. I have just bought this truck, I am happy with it apart from a clunk? It appears to be coming from the steering wheel shaft? When I turn the wheels ( truck in motion or stationary ) I hear a grinding clunk, any suggestions?

Try changing the power steering fluid. If the problem persists, the rack & pinnion may be bad.

GM Service Bulletin 00-02-35-003N addresses that issue. This is an updated part number for the upper intermediate steering shaft with a part number: 19153614.
It installs quickly and doesn't require realigning the front suspension.

If the intermediate steering shaft is the problem, you should be able to remove it, press out the universal joint, repack the joint with NLGI #2 wheel bearing grease (preferably synthetic), and press in the U-joint.