A Solution!
Rather than start a new thread, I'll put it here since there are good discussions and descriptions previously. Yeah, I've been having strange noises from the rear, coming and going. In the process of installing a rear sway bar, I found a major part of at least my problem. To do it, the lower shock bolts are removed and the trailing arms of the suspension rotated down. This makes the springs easy to remove. Besides being squeezed between the body and trailing arm, there is a spring locator "cup" on top and bottom (see first picture). The spring top and bottom slips over the cups to keep them in place. Between the cup / mounting surface and the spring is a rubber pad to prevent metal-to-metal contact.
When I pulled the springs out, on the top side of one, the end of the coil had punched through the rubber (see second picture). Based on the shiny metal, a sharp edge of the spring had been rubbing directly on the locator "cup". I rounded off the offending edge using a Dremel with a stone, then replaced the following parts:
1 x Insulator, Part #90538496 @ $3.91
2 x Shock Bolts, Part #11610587 @ $1.82
One irritation gone!
BTW, it's a pretty easy DIY job for an experienced DIYer. No spring compressor needed. Though do replace the shock mounting bolts with new; they are torque-to-yield which means that once loosened, they're trash.
