Finally think I solved my vibration issue

Can you get it to vibrate sitting still? In other words does it vibrate at 3000 rpm in park?neutral? If so, I would rule out everything from the trans back. If it is at a roll, it could be the driveshaft ( bent,twisted, out of balance) or in thr rear diff. Bent axles, bad bearings etc. I had a similar situation in a stick shift car, turned out to be a pressure plate that was out of balance and a driveshaft that needed balancing. I had a vibration sitting still, and at a roll. Check everything, also, don't count out the internals of the transmission either. There are bearings and output shaft bushings that can cause issues. Through the process of elimination, I removed the worst of it ( the pressure plate) then smoothed it out with the driveshaft rebuild.