I had some driveshaft shake but it was because I had shitty polyurethane transmission bushings that compressed way too much after installation and caused the driveline to be out of alignment at and shake like hell at certain speeds. Swapped driveshafts, guibos and CSBs plus pulled out the diff and inspected it and it still didn't go away.
Just put the new bushings in yesterday (Condor Speed Shop's UHMW bushings) and went for a quick drive. No more vibration. On the up side, I now have a spare everything to do with the driveshaft. Replacing your CSB will likely fix your problem though if it's snapped. Not a fun job, but pretty easy to do.
"She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself. " - Han Solo