Ditto what VXorado said.

When my inner CV boot ripped, and I didn't catch it until it was too late, I was getting some vibrations at various speeds that I thought was a drive shaft issue or a transmission mount issue. Got under the VX, greased the U-joints, and slip joint in the drive shaft, checked the transmission mount bolts and still had the vibrations. Checked the CV joints on the front axle and realized that the boot was torn, and gunk had gotten in there and effed up the joint. Had to have the green cup removed and re-machined.

Since the front axle is hard mounted to the frame, I was feeling the vibrations from the bad drivers side inner CV joint in the floor boards below my feet.

Also, check the transmission mounting bolts. Others have had some vibrations, or clunks, due to the bolts backing themselves out allowing the transmission to move around.

One more shot in the dark; check your engine mounts. If one is bad/broken it would allow things to move around and possibly cause a vibration.