I have a spare d-shaft in my garage if anyone knows how I can get rid of it ?
Definitely keep it until you’ve solved the current vibration problem. You may still need to use it to test the various theories. You were very wise not to discard it or exchange it. Once you know you don’t need it – the vibration is solved or you’ve sold the vehicle – take your driveshaft to a local driveshaft-experts repair shop. There’s usually one in every populated area, since driveshaft problems are a pretty common thing, especially on trucks. They will likely be willing to make you an offer for it. Before doing that you might offer it up on Craiglist, just in case somebody is looking for that exact one. In which case you’ll get a better price. If nobody wants it, use it to reinforce your next concrete pour.