help me please...drive train

i have a cj-7 (79) golden eagle. had it since birth. never a problem with drive train... then last week, doing about 20 it got a vib.. that felt like u-joints, come and go. took it to shop..checked everything, brakes, rear end, u-joints, bearings, everything behind trans..manual. to no avail. vib continued even when 304 was shut off...any help here. e-mail me [email protected]

either seized u/j. take off and check.or engine g/box mounts.other, could be bad tyre.