Dale, the 4 link with a watts refers to the rear suspension being a live axle with 2 trailing arms on each side which locate the the rear end fore and aft and through virtical movement. These 4 links are also responsible for the pinion angle.
The watts link is a pair of rods located on each side of the car's frame and attached to the back of rear end housing by means of a rocker (link) which will allow virticle movement of the rear but stop any lateral movement.
http://www.youtube.com/watch?v=blDJ-...eature=related
Lots more going on there but these are the basics. And for what it's worth; if the pinion angle is the cause of the noise (which I doubt) and it's so easy to fix (just a turn of the nuts) then why hasn't he already done it?