Hey guys, OP here with a few added thoughts for you. Glad to see this is back from the dead again and still useful to people.
Close examination of the orientation of the bushings will reveal an important truth....their axis is not horizontal with the car. The bushings are tilted, yet the axle by design must
rotate on a horizontal axis...so what does this mean?? It means the bushings are subject to twisting forces as the axle pivots up and down. It undoubtedly has to do with some kind of bias the engineers were trying to create, most likely to affect some toe or camber angle during articulation. Bottom line -- any poly bushing back there is going to squeak, in theory, because of the way it is being twisted every time you hit a bump. This is entirely different than what happens on a front control arm, where the bushing's axis IS inline with the pivot of the arm. The two cannot be really compared.
As far as why do this at all, that was covered in the original post. Crappy bushings are just....crappy. No one wants slop in their drivetrain, and VW's feel soooooo much better when everything is fresh. Plus the fluid-filled bushings are eventually going to leak.
Finally, let me say I am parting out the car. So hit me up if you wold like to possibly buy this entire axle. It has 20th rear brakes, an Autotech hollow sway bar, hubs and bearings were new at the time of the write-up (only put about 15K on the car since then), and they have a stud conversion on them.
Modified by RabbitsKin at 11:46 PM 4-14-2009