Dunno about the G*, but have heard very few Commondore SS owners with issues.
That being said, there's and SV-6 at work that has scared the carp out of it's driver a few times with rear end "crashing" noises.
Drove two identical Ford XR-6s and found one with majorly nasty drivetrain snatch, and the other a delight.
Stick on wheel weights on calipers is lame.