POTENTIAL CAUSE
1. Loose engine accessories:
– Alternator
– A/C compressor
– Power steering pump
– Mounting brackets
– Pulleys
– Belt tensioner
– Serpentine belt
– Drive pulleys
2. Torsional damper damaged or loose.
3. Flywheel (drive plate) cracked or loose.
4. Torque converter imbalance caused by internal damage or missing balance weight.
CORRECTION
1. Check and repair as needed. Replace damaged missing bolts and apply Loctite 242 to loose bolt threads. Replace serpentine belt if damaged.
Replace bent, broken pulleys.
2. Replace damper if damaged, worn, loose.
3. Replace flywheel and also check for ballooned or damaged converter.
4. Replace converter.