Is drive shaft on 88 Lincoln Mark VII a two piece unit with one on the inside of the other? I replaced the three u-joints and cardan ball joint. Checked ring and pinion, excellent. All wheel bearings, good. Still getting clangging and vibration in drive shaft. Clangging from 0 to 25mph. Vibration begins really noticible at 50 mph and up. On hoist, mechanic says there's something lose inside drive shaft that it is a two piece unit with one inside the welded up outer (from the factory).