I've had the Helwig and Radius rods around 8 months..had a mechanic install both. I started getting a clunking noise if I hit something which caused a vertical and horizontal torgue--ie. cutting into a parking lot. I could not see anthing when I crawled under so I took it back to the mech. Up on the lift, the right side mounting bolt to the frame had backed out ssome and the top of the bolt was banging against the leaf sring--scraping up and down. These are locking nuts so maybe he did not tighten that one well originally. You have to stick your hand between the muffler and I beam to get at the bolt. Anyway, it's something else to check if you gat a noise in the back.
did you get this noise when braking also?
I am getting a clunk sometimes when braking that I cannot figure our.
I am waiting on my new shocks and Helwig rear sway to dig more into it