Re: process of elimination - vibration
Vibration issues are many times not so easy to find. Removing the front DS is a good start (put a mark on the couplings, so that you will put it back in the same position as it was before, otherwise you could end up with even more vibration) . Maybe also balancing the wheels to rule out unbalance. Did this vibration suddenly start, or was any kind of maintenance done?
Regarding the DS, there are some balancing weights soldered on them, just check if they are not gone (they are quite small on my Jeep, so don't know if missing them would make a big difference)