I had this happen to my 98 E320 with 78,600 miles. My wife was driving at the time it happened traveling at 35 mph and about 5 miles from home.

The only damage it did was shread the edge of the drive belt and put a small gouge in the timing chain cover. The rubber from the balancer looked like it sheered from torque by the way it separated. This caused the balancer to shift back toward the engine causing the gouge and shreading of the drive belt.

I ordered a replacement crankshaft balancer and drive belt from Phil and replaced it myself. I also filled the gouge with JBweld.

Its been 5K miles since I replaced it without any problems. (Except for the "Check Engine Electronics" message).

FYI - my 98 E320 was manufactured in the fall of 97.

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Ray
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles