I just had a higher freq vibe (more a sound than a real vibe) after the tranny swap. Driveshaft type
..... even though the joints were replaced and the shaft balanced.
Well, I re-torqued the pinion nut and rotated the drive shaft flange 180 degrees (relative to the diff input) and voila - all smooth
.
If you get a low freq "shudder" when under load the front axle inner joints could be worn. A low cost trial is to swap the axles L/R.
Tapani
PS I have a very soft rubber disc in the steering column shaft - this causes some play and sound. Also the inner tierod ends were worn - easy enough to swap w/o pulling the rack.