He also had a failed hub bearing on the rear. The front is where he busted the pin on the pressed in bearing. A failed (or failing) rear bearing can also cause a vibration (+ possible clunking) on weight transfer.In case you are referring to, the front arm uniball failed. We have zero failures with our GMS uniball rear arms so far.
Other common reasons for "creaking" or noises from the back end
1) Swaybars: Some aftermarket sway bars are missing the cap to hold the rubber in place and may move causing a creaking noise (Sector111). The bolts holding the sway bars can also loosen with heavy track use (use Locktite)
2) Upper Strut Mounts: Some aftermarket struts remote reservoir tube can hit/rub the cars mounting bracket for the strut.
3) Lower Strut Mounts: The lower bolt on the struts that clamps the strut to upright have been known to loosen (again track use). If you lift the car, you can wiggle the tire. Not sure if it will clunk, but it will wiggle tires.
4) Lower A-arm uniballs loose: If you didn't measure the A-Arms hole prior to insertion and the hole was too large, then the uniballs can loosen and shift off center. They will eventually come in contact with the car's arm brackets and make a hell of a racket when hitting bumps and weight transfer.
5) Failed uniball: As Gale noted, none of the uniballs have failed once correctly installed (yet, but they will eventually). IF the shop who did the install didn't press in correctly, they may have damaged the uniball....
6) Ball joint: The ball joint can fail, and will cause creaking and noise.