My 95 Bronco had a lift and sat on 35's. I had an unloaded vibration at 55-70mph. I replaced the tires, and had the driveshaft rebuilt and rebalanced but the vibration was still there. On a whim I swapped in a transfer case I had laying around and the vibration went away. Never did figure out what was wrong with the transfer case. Everything felt tight and smooth.
1997 CCSB, 7.3/E4OD
KC TP38R, CNC Fab Bellowed Up-Pipes, Full Force Stg 1 injectors, 3" DP, 4" exhaust, CNC Fab HPOP, Mark F E-Fuel, 7.3 Intercooler, 1.0 Exhaust Housing, TS Chip, remote coolant filter, and VB.