olcoacher, your noise is coming from the lower shock mounts more than likely. You can prove this by crawling under the truck and then pushing up on the spare tire. If you watch the lower shock mounts, you will see the whole shock move a little bit and then stop as you lift up on the rear.
As for the fix, you can first try tightening on the lower mounts to see if you can make the support clamp on to the shock properly. Works for some, doesn't work for others. Now, when i say tighten, I mean TIGHTEN!!!!! The term Spot Torquing is applied here.
After that, you can try finding a large fender washer that just barely fits over the bolt. The problem is that somewhere, all the aftermarket manufacturers got the wrong diamensions for the sleeves in the lower mounts. So, they are made about 1/8" too short. So, what you will need to do is to remove the lower bolt, slide the washer between the shock bushing and the support on the axle and then tighten everything back up. That may be enough to get the clamping force on the metal sleeve and not being applied to the rubber bushing.
What I ended up doing was machining some sleeves to put into the lower bushings that were the proper dimensions. You can probably get a machine shop to make you a set and it will run you about $25 or so.
I bet you replaced your shocks about 5,000 miles ago didn't you?
