I just took my prg shackles off for the third time since I have had them , because of that damn squeak and seriously greased the living sh** out of them. (with lithium hi temp grease, usually lasts bout 4 months)
While I was back there I noticed the bushings were grooved from a little tab left on the lower shackle seat, by the factory. So I pulled out the trusty dremmel with grinding ball attachment and smoothed the hell out of those
tabs. It has been a week and not a sound, hopefully that is the answer your looking for.
That traction bar issue you are refering to pisses me off too, but all I do is crawl up underneath and retorque the bolts at both ends of the bars and it works for awhile