Very common. Do you still have the 2 rods that run from frame to the engine in the bellhousing area? If not that is the problem ,if so make sure they are tight and all bushings etc are there. The cause is the engine moves back and forth as the clutch is engaged which makes the clutch grab and release making the chatter. If all the rods parts are in order you may need a new clutch ***y ,a disk at the least.
The Jalopy Journal
